The changes in blood pressure in the right atrium are the same as those in the left atrium. The changes in blood pressure in the right ventricle are different from those in the left ventricle.
(both) atria pump blood to ventricles ; same / short, distance ;
right ventricle pumps blood to lungs ; short distance / at low(er) pressure / at approx 3.2 kPa / at approx 24 mmHg ; ora i.e. (left ventricle) greater distance / high(er) pressure / at approx 15.8 kPa / at approx 120 mmHg less resistance, in lungs or pulmonary circulation / greater resistance in the systemic circulation ; left ventricle pumps to, whole body / AW ; correct ref. to (muscular) walls ; e.g. same (thickness) in atria thicker / thinner, in ventricles more / less, muscular, in ventricles right ventricle pumps with lower / less, force ; ora
Some components of tobacco smoke are absorbed into the blood stream and affect the cardiovascular system.
Describe the effects of nicotine on the cardiovascular system
nicotine increases heart rate ; increases blood pressure ; makes platelets ‘sticky’ ; increases chance of blood clotting / promotes thrombosis ; decreases flow of blood to, extremities / AW ; constriction of blood vessels
Some components of tobacco smoke are absorbed into the blood stream and affect the cardiovascular system.
Describe the effects of nicotine on the cardiovascular system
carbon monoxide combines with haemoglobin / forms carboxyhaemoglobin / higher affinity for haemoglobin (than oxygen); R absorbed, reacts with, bonds to reduces oxygen carrying capacity (in context of, haemoglobin / blood) ; promotes release of damaging free radicals / peroxides / super oxides / oxidising agents ; causes platelets and neutrophils to stick together / platelets to stick to endothelium ; hypoxia can damage heart muscl
Describe the roles of centrioles in animal cells.
(during), mitosis / meiosis / nuclear division ; ignore ‘cell division’ / phases replicate, after / before, each division ; A at interphase move / separate, to poles ; assemble / organise, microtubules ; centre for growth of / forms, spindle fibres / for formation of spindle / AW ; modified centrioles found elsewhere such as in flagella / cilia ;
) Explain why it is possible to see the internal membranes of a cell in electron micrographs, such as Fig. 2.1, but it is not possible to see them when using the light microscope.
(EM has) greater / higher, resolution / resolving power ; ora explanation of resolution as ability to differentiate between two points (close together) ; width of membranes is 7 nm (±1) ; (resolution of) LM is 200 nm (0.2 µm) and EM is 0.5 nm (0.0005 µm) ; A 0.5 to 1 nm (0.001 µm) ref to shorter wavelength ; ora resolution is equal to half the wavelength ;
explain the effect of increasing temperature on the beetroot tissue.
at (temperatures above) 60 °C, cell / vacuolar, membranes damaged / AW; A tonoplast (membrane ) proteins, denatured / altered tertiary structure ; increased fluidity (of membrane) / phospholipid bilayer more fluid ; (so) diffusion / AW, of, betalain / pigment (out) ; as temperature increases, rate of diffusion increases / diffusion occurs more quickly
structure of collagen
more than four (different) monomers (monomers =) amino acids / polypeptides no sugar no base(s) strands not antiparallel peptide bonds no phosphate / phosphorus A sulfur (sulphur) present left handed helix tightly coiled triple helix A three stands
structure of dna
4 (different) monomers (monomers =) nucleotides / polynucleotides double helix right handed helix loose helix sugar antiparallel strands phosphodiester bonds base(s) phosphate / phosphorus
State what is meant by the term tidal volume.
volume of air breathed, in / out, with one breath
Explain how the minute volume at rest would be determined
before / after recovery from, exercise ;
either measure tidal volume, by breathing out into a bag ; multiply by number of breaths per minute ; A total tidal volume in x minutes ÷ x
or use a spirometer / described ; ref to taking recordings from a trace / use of a, kymograph / datalogger
Suggest two differences in the structure of the lungs that may account for the greater oxygen uptake by people who live on top of mountains
(bigger lungs so) more alveoli ; A greater surface area (of alveoli) more, bronchioles / airways ; R more bronchi wider, bronchioles / airways ; larger number / higher density, of capillaries (around alveoli) ; thinner wall / shorter distance, between air and blood / AW ;
Explain why the red blood cell count increases so much when people visit places at high altitude.
partial pressure of oxygen is low ; A low concentration of oxygen / less oxygen more haemoglobin (is required / produced / synthesised / available) ; compensates for smaller volume of oxygen absorbed / compensates for lower saturation of haemoglobin / more oxygen can be carried (per unit of blood) ; ref to, EPO / erythropoeitin ;
Suggest how organisms that live in freshwater that has a low concentration of sodium ions. and who’s body fluids have a higher concentration of sodium ions than the surrounding water, retains sodium ions in its body fluids.
cell membranes impermeable to sodium ions ; (as) sodium ion channels are not present (in cell membranes) ; active transport / active uptake ; A sodium pumps to take up sodium ions move sodium ions against their concentration gradient ; uses, energy / ATP ;
State one role of sodium ions in organisms.
ref. to, (nerve) impulses / action potentials / depolarisation / resting potential ; treat ref. to electric as neutral helps to maintain, water / solute / osmotic, potential of, body fluids / named body fluid ; helps to maintain, osmotic / electrolyte, balance ; ref. to, urine formation / osmoregulation ; absorption of glucose / co-transport ; [1 max]
flatworm which lives in ponds, streams and rivers. The dimensions of the flatworm are 12.5 mm long by 3.0 mm wide. Its volume was estimated as 12.6 mm3. Flatworms do not have a transport system for the respiratory gases, oxygen and carbon dioxide.
explain how flatworms survive without a transport system for respiratory gases.
thin / flat ; large / high, surface area to volume ratio / small / low, volume to surface area ratio ; R large surface area (on its own) (SA:V ratio) 5.95:1 ; A anything between 5:1 and 7:1 or suitable calculation e.g. 2 × (12.5 × 3.0) / 12.6
state two ways in which the structure of catalase is similar to the structure of haemoglobin and one way in which it differs
similarities
made of amino acids / amino acid monomers / polymer of amino acids A protein / polypeptides have quaternary structure / have more than one polypeptide chain ; four, sub-units / polypeptides ; haem / porphyrin / prosthetic group(s) ; [2 max]
difference
(four) sub-units / polypeptides, are identical ; or haemoglobin has, two different, sub-units / polypeptides ; or haemoglobin has alpha and beta polypeptides ;
(catalase) has active site(s) ; A Hb has (oxygen) binding site
State why it is possible for a catalase molecule to bind to four substrate molecules at the same time.
each, sub-unit / polypeptide, has an active site ; catalase has four, active sites / haem groups ;
Explain, in terms of water potential, how water moves from across the leaf
water moves down water potential gradient ; A high(er) to low(er) water potential / less negative to more negative water potential apoplast pathway / through cell walls ; symplast pathway / through, plasmodesmata / cytoplasm ; evaporation ; from spongy mesophyll cell walls ; into (substomatal / intercellular) air space ; diffusion of water vapour ; A diffusion of water if evaporation used in correct context elsewhere through stomata ;
State and explain three ways in which the structure of xylem vessels is adapted to transport water.
cellulose, cell wall / lining ; allows adhesion of water ; and prevents collapse providing support under tension
either lignin ; waterproofing / prevents water loss ; or lignin ; A rings / spirals / thickening / AW (of walls) prevents collapse / idea of providing support (under tension) ;
no cytoplasm / lack of contents / hollow / empty lumen ; R dead less resistance to / unimpeded / uninterrupted / unhindered / ease of / AW, flow / AW ; A greater volume per unit time / faster rate R continuous, smooth
lack of end walls / continuous tube ; less resistance to / unimpeded / uninterrupted / unhindered / ease of / AW, flow / AW ; R continuous, smooth
pits / pores ; R holes lateral movement / movement around air bubbles / supplies (water) to (surrounding), cells / tissues ;
wide / large diameter / large lumen ; so large volume of water can be transported ;
how do you know a cell is in metaphase
chromosomes / chromatids, on equatorial plate / at equator / AW ; A in, centre / middle, of cell nuclear, membrane / envelope, dispersing / breaking up / (partially) visible / AW ; A disappearing chromosomes, in one group / not in two groups / not arrow shaped / not going to poles / not separated / AW ;
Describe how cigarette smoke is responsible for the development of lung cancer.
smoke / tar, is carcinogenic
genes control, cell division / mitosis ;
mutation / change to DNA (in these genes) ;
tumour suppressor genes switched off cells,
uncontrolled mitosis
cancer cells do not respond to signals ;
(and) form a (malignant) tumour ;
(tar) settles on bronchial, epithelial cells / epithelium ;
State and explain two ways in which the structure of a phloem sieve tube is adapted for the transport of assimilates.
sieve pores ; allow easy flow (from sieve tube element to sieve tube element) ; R flow of water
sieve plate ; (may) prevent sieve tubes from bursting / AW ;
cell (surface) membrane / plasma membrane ; prevents loss, of sucrose / assimilates / phloem sap ; little cell contents / AW ; R no cell contents little resistance / AW, to flow ; R flow of water
plasmodesmata ; allows flow, to / from, companion cells ;
thin walls ; for, rapid / easy, entry of water (at source, to build up pressure)
Describe the function of the endodermis in roots.
Casparian strip / suberin, is impermeable (to water) ; blocks, apoplast pathway / pathway between cells / cell wall pathway ; ref. to passage cells ; water / (inorganic) solutes / minerals / ions, must pass through, endodermal cells / symplast pathway / symplast pathway described ; cell can select solutes / AW ; ref. to, active transport / carrier proteins ; ref. to presence of solutes (at base of xylem) causing increase in root pressure / AW
State two roles of water within plant cells other than taking part in breakdown reactions
accept any two relevant examples, e.g.
solvent / medium for reactions ;
transport medium ;
maintaining turgidity / keeping firm / prevents flaccidity / AW ;
(raw material / reactant for) photosynthesis / photolysis ;
expansion / elongation / growth ;
maintains, hydrostatic pressure / pressure potential ;
maintains water potential (gradient) ;
A maintains osmotic gradient / prevents plasmolysis
stomatal opening ;
hydrophilic interactions of membranes ;
(in vacuole) pushes chloroplast to edge of cell ;
R hydrogen bonding unqualified by ref. to membranes
Describe the role of elastic fibres in the wall of the alveolus
stretch / expand / lengthen, on inspiration and, recoil / shorten, on expiration ;
A alternatives for inspiration and expiration but R contract and relax
(stretch) to increase, surface area / volume of air, for, diffusion / gas exchange ;
(recoil) to (help), expel air / force air out ;
explain how alveoli are adapted for gas exchange.
correct ref. to diffusion of, carbon dioxide / oxygen ; A absorb / lose / AW
(many alveoli) large surface area ;
surrounded by, (many) capillaries / capillary network / AW ;
short diffusion distance (between air and blood) ;
blood maintains concentration gradient ;
epithelium / alveolar wall / AW, thin / squamous ; A alveolus one cell thick
A alveolus has a thin wall
R cell wall e.g. alveolar cell wall is thin
idea that very little between, epithelium and endothelium / AW ;
e.g. alveolus and capillary are close together
State two ways in which the lung tissue of someone with emphysema differs from the lung tissue of someone with healthy lungs.
assume answers are about person with emphysema, accept ora if clear
fewer alveoli / (large) ‘holes’ ;
A alveolar walls broken down / fewer air sacs / alveoli burst / destroyed
less / destroyed / broken, elastic tissue / elastin ; ignore damaged
R no, elastin / elastic fibres
small(er) surface area ;
fewer capillaries ;
named change(s) to bronchial tissue ; e.g. enlarged goblet cells, more mucus, scar
tissue, scarred, narrow lumen in airways, inflammation, damaged / no, cilia
ref. to tar deposits ;
State two symptoms of emphysema
shortness of breath (when exercising) / breathlessness ;
A breathing difficulty
wheezing / AW (on inspiration) ;
rapid breathing rate / hyperventilation / decreased ability to hold breath ;
R heavy breathing
chest, tightness / pain ;
cyanosis / bluish appearance to the skin / AW ; A pale
fatigue / tiredness / lethargy / weakness / dizziness / AW ;
coughing / coughing up blood ;
lots of mucus produced / much phlegm ;
expanded / barrel, chest ;
Explain how the valves ensure one-way flow of blood through the heart.
allow ref to one side only valve opens to allow blood from atria to ventricles ;
when ventricles contract, valves close (to stop backflow) ;
A valves close when blood is pumped out of the ventricles
ref. to pressure difference between chambers ;
Explain the roles of the sinoatrial node (SAN), atrioventricular node (AVN) and the Purkyne tissue during one heart beat.
SAN sends out, wave of excitation / impulses ; A electrical (im)pulses
R once only - nervous impulse(s) / pulse(s) / signal(s) / wave(s)
R if brain stimulates SAN to send out impulses
2 spreads across atria ;
3 atria contract / atrial systole ;
4 fibrous ring / non-conducting tissue / insulating tissue ;
5 prevents, it reaching the ventricles / ventricles contracting at the same time (as atria) ;
6 AVN sends on wave of excitation to ventricles ;
A in context – impulse reaches AVN and is passed on to ventricles
7 (therefore) time delay to allow, atria to empty / atria to complete contraction / ventricles
to fill / atria and ventricles do not contract at the same time ;
8 time ref. 0.1–0.2 seconds ;
9 Purkyne tissue conducts, excitation / impulses, to base of, septum / ventricles ;
A apex of heart
10 spreads upwards in ventricle (walls) ;
11 (so) ventricles contract from base upwards / ventricles force blood up from base ;
State two ways in which the composition of blood entering the right atrium is different to blood entering the left atrium.
right atrium has (ora for left atrium)
lower, concentration/partial pressure/AW, of, oxygen ; R no oxygen
A (right) deoxygenated blood (versus oxygenated blood)
A higher saturation of haemoglobin with oxygen
higher concentration/AW of, hydrogen carbonate ions/carbon dioxide ;
A more carbaminohaemoglobin
higher concentration of water molecules/high(er) water potential/less negative water
potential ;
higher concentration/AW, of glucose ;
patent ductus arteriosus – a link between the pulmonary artery and aorta fails to close after birth
Suggest and explain how the flow of blood in a person with patent ductus arteriosus differs from that of a person with a healthy heart.
suggest
1 blood flows from aorta to pulmonary artery ;
2 increased volume of / more, blood to lungs ;
A blood to lungs at higher pressure
3 oxygenated and deoxygenated mix ;
4 oxygenated blood / blood from aorta, to lungs ;
explain (why blood flows from aorta to pulmonary artery)
5 left ventricle thicker wall (than right ventricle) ;
6 (so) contraction generates greater force (than right ventricle)/AW ;
7 higher pressure in aorta (than pulmonary artery)
Explain the role of goblet cells in the maintenance of a healthy gas exchange system
synthesise/produce/secrete/release, mucus ;
mucus, sticky/AW ;
(mucus) traps/AW, pathogens/AW , dust/particles/AW, pollen ;
A named organism types/microorganisms
R cilia traps
increased secretion when, inflamed / infection ;
qualified ref. to role of mucus ; e.g.
increases distance (e.g. of pathogen) to reach (epithelial) cells
acts as barrier/prevents, entry/attachment to, cells
prevent, infections/pathogens reaching alveoli
Explain the role of cilia in the maintenance of a healthy gas exchange system
waft/move/AW, mucus ;
synchronous/metachronal, rhythm ; AW
movement towards back of throat for, swallowing/coughing out ;
qualified ref. to role of cilia in health ; e.g. ref. to, normal air flow/ventilation/keeping airways
clear
why is left ventricle s wall thicker than the right ventricle
(Y/wall of left ventricle) contains more (cardiac) muscle ; ora
left ventricle/ventricle beside Y, pumps blood to, whole body / further ; ora
at higher pressure with more force (than right) ; ora
resistance to blood flow is greater in systemic circulation ;
Name the medical condition caused by breakdown of the elastic fibres
(ii) emphysema
Cigarette smoke contains tar, a substance which has several harmful effects on the cells lining the gas exchange system.
Outline three of these effects.
(cause) mutations ;
uncontrollable, division/mitosis/cell replication/cell growth ;
lack of contact inhibition/no apoptosis or described/(proto)oncogenes ;
goblet cells secrete, excess/more/AW, mucus ;
destroys/weakens/paralyses/AW, cilia ;
development of scar tissue ;
inflammation ;
increased chance of infection/AW
Explain the importance of the effect of carbon dioxide on haemoglobin
carbon dioxide influences percentage saturation of haemoglobin with oxygen / AW ;
2 tissues / cells, with high rate of (aerobic) respiration ;
3 high demand for oxygen ;
4 haemoglobin / blood, releases more oxygen ; R faster
5 than it would in absence of carbon dioxide ;
6 at same partial pressure of oxygen ;
The percentage saturation of haemoglobin with oxygen decreases as the partial pressure of carbon dioxide increases.
Explain how this happens
either
react or combine with haemoglobin / form haemoglobinic acid / form HHb ;
A ‘picks up’ / absorb
or
carbon dioxide combines with haemoglobin / forms carboxyhaemoglobin ;
(so) stimulate haemoglobin to release more oxygen (in areas of low pO2) ;
ref. to, allosteric effect / change in tertiary or quaternary structure or shape ;
A conformational change
either
haemoglobin has a higher affinity for hydrogen ions than oxygen = 2 marks
or
haemoglobin has a higher affinity for carbon dioxide than oxygen = 2 mar
role and importance of carbonic anhydrase
(catalyses very) fast / AW, reaction ;
(carbon dioxide as) hydrogen carbonate ions / bicarbonate ions ;
diffuse / move / leaves, out of the (red blood) cell ;
in(to) the plasma ; R ‘into blood’
(so that) blood can transport more than could be transported as carbon dioxide (in
solution) / 80 – 90% CO2 transported this way ;
idea that
reaction maintains concentration gradient for CO2 from, tissues / tissue fluid, to blood ;
if carbon dioxide transported then pH would decrease ;
(therefore) maintains pH / prevents pH decreasing / acts as a buffer ;
State three ways in which the blood at venules differs from the blood at the artefioles other than in the concentration of carbon dioxide.
assume answer refers to Y unless told that it refers to X
less pressure ; A low pressure
less oxygen ; A deoxygenated
less glucose ; only accept more glucose if identified as liver
fewer / more, amino acids / fatty acids ;
less water / lower water potential / lower solute potential / higher osmotic pressure / higher
concentration of solutes and / or rbcs ;
A ‘blood is more concentrated’
fewer ions ;
more of named cell product ; e.g. insulin / glucagon / albumen / AW
(more), urea / excretory waste
Describe how carbon dioxide molecules reach red blood cells from respiring cells
diffusion / diffuses ;
down concentration gradient / from high concentration to low concentration / from high to low
partial pressure ;
description of pathway ;
two of the following
cell (surface) membrane of (respiring) cell, tissue fluid, (pore in) capillary wall / endothelium /
endothelial cell, basement membrane / plasma
Explain how the structure of red blood cells is suited to their function of transporting oxygen to body tissues
small size / 6-8 µm (diameter), to squeeze through capillaries (7 µm) ;
2 small size / 6-8 µm (diameter), so, haemoglobin (molecules) near to surface (of plasma
membrane) / reduces distance for diffusion (in / out of rbc) ;
3 no nucleus / lack of organelles, so more room for haemoglobin (so more oxygen
transported) ; R more room for oxygen
4 biconcave shape / diagram drawn, increases surface area for, diffusion / uptake / release
(of oxygen) ;
5 flexible / AW ( membrane), to squeeze through capillaries ;
The circulating red blood cell is metabolically active but only lives for about 120 days. During this time, some important enzymes are gradually broken down and this may contribute to the death of the cell.
Explain why the red blood cell is not able to replace important enzymes that have been broken down.
1 enzymes are proteins, protein synthesis does not occur ;
2 no, nucleus / DNA / genes, so no, transcription / mRNA ; *
3 no mRNA, so no, translation / protein synthesis ;
*A no nucleus, so no protein synthesis for one mark
4 no, RER / ribosomes, site of protein synthesis / AW ;
5 no mitochondria, insufficient ATP (for synthesis) ;
6 no RER for modification (of protein) ; A Golgi apparatus
describe and explain how carbon dioxide (CO2) and hydrogen ions (H+) play a role in the unloading of oxygen from haemoglobin
diffusion of, carbon dioxide / CO2;
2 into red blood cell from correct source ;
3 description of carbonic acid formation followed by H +
production ;
4 ref. carbonic anhydrase ) fast reaction; A ecf from (d)
5 haemoglobin has a higher affinity for hydrogen ions than oxygen ;
A haemoglobin releases oxygen more easily in acidic conditions
accept idea of H + binding to haemoglobin bringing out oxygen release
6 ref. to, allosteric effect / change in tertiary structure / AW, in (oxy)haemoglobin, causes,
release / AW, of oxygen ;
7 formation of haemoglobinic acid ; must refer to, H +
binding / decreased pH
8 ref. higher partial pressures / AW, CO2, linked to (oxy)haemoglobin releasing, more
oxygen / oxygen more readily ; Bohr shift
9 formation of carbamino-haemoglobin ; R carboxyhaemoglobin
10 chloride shift, qualified ;
e.g. as hydrogen carbonate ions move out of cell, chloride ions move in e.g. to maintain,
electroneutrality / a balance of charge / ions ;
Describe and explain the effects of nicotine on the cardiovascular system that can contribute to a person developing coronary heart disease
ref. to coronary arteries ; in correct context makes platelets sticky, so causing blood to clot ;
increases risk of thrombosis in, coronary arteries / arteries to heart (muscle) ;
leading to plaque / atheroma / atherosclerosis / AW ;
increases heart rate ;
increased blood pressure ;
damage to, tunica intima / endothelium /endothelial lining / arterial lining
The production of low-nicotine cigarettes and cigars is considered a strategy that may reduce the harmful effects of smoking.
Explain whether or not you agree with this statement.
agree
less addicted to smoking cigarettes so fewer smoked ;
fewer smoked, so reduced risk of smoking-related diseases ; A named disease
fewer smoked so reduced risk from, (effects of) tar / carbon monoxide ;
disagree as people may smoke more
may smoke more to, increase their nicotine levels / satisfy need for nicotine / AW ;
more smoked, so increased risk of smoking-related diseases ; A named disease
may smoke more so increased risk from, (effects of) tar / carbon monoxide ;
Plants take in mineral ions through their root hair cells. This may happen by a process which moves the ions from a low concentration in the soil to a higher concentration in the root hair cell.
(i) Name and describe this process by which mineral ions are taken in
active, transport / uptake ; [1]
carrier / transport, protein ; A pump protein R channel protein
ref. (protein) changing shape / conformational change ;
ref to specificity ;
ATP / energy, required ;
Water is also absorbed from the soil by the root hair cells.
Outline the mechanism by which this occurs.
osmosis in correct context ; e.g. through, cell surface / partially permeable, membrane or
into, cytoplasm / cell
diffusion, into / through, cell walls ;
from (region of), high(er) / less negative, water potential, to (region of), low(er) / more
negative, water potential or down a water potential gradient ;
transpiration pull ;
Describe the pathway taken by water as it passes from the root hair cells into the cells which are specialised for transport of water and mineral ions.
through cortex / via cortical cells ;
apoplast pathway
(by) via cell walls (of adjacent cells) ; R if named as symplast pathway ;
symplast pathway
via cytoplasm and plasmodesmata ; R if named as apoplast pathway
ref. vacuolar pathway ;
ref. apoplast to symplast / pathway described, at endodermis ;
(via) passage cells ;
ref to, suberised / Casparian, strip ; in correct context
There is a large difference between the percentage saturation of myoglobin and that of adult haemoglobin at low partial pressures of oxygen. Suggest reasons for this.
myoglobin has higher affinity for oxygen / myoglobin binds oxygen while haemoglobin
releases oxygen ; ora
(myoglobin) acts as a store of oxygen ;
myoglobin will only release oxygen, at (very) low oxygen partial pressures / AW when
oxygen demand (in muscles) exceeds supply ; A during exercise
AVP ; e.g. myoglobin has, one / fewer haem groups, so no cooperative binding effects
e.g. allows aerobic respiration to continue (in muscle)
Explain, with reference to Fig. 4.1, the significance of the difference in oxygen binding affinity between fetal and adult haemoglobin.
fetal haemoglobin has higher oxygen affinity (than adult / maternal haemoglobin) /
AW ;
(higher oxygen affinity) over all ppO2 / use of data at more than one ppO 2 (from
Fig. 4.1) ;
oxygen uptake from, adult / maternal, blood / AW ;
or
gas exchange taking place between fetal and, adult / maternal, blood ;
ref. to fetal reliance on mother to supply oxygen / mother only source of oxygen for
fetus ; [2]
In a rare condition known as Hereditary Persistence of Fetal Haemoglobin (HPFH), fetal haemoglobin continues to be produced well into adulthood in addition to adult haemoglobin. This condition, however, usually lacks any symptoms.
Suggest why HPFH usually lacks symptoms
at lower ppO2 both, unload / AW, oxygen ;
sufficient / more, adult haemoglobin present or adult haemoglobin provides sufficient
oxygen / AW ;
ref. to compensating by producing additional red blood cells ;
AVP ; e.g. ref. to similarity of position of both curves
For Examiner’s Use
(c) Describe how the assimilate you have named in (b)(i) is transported from the source to the sink.
1 H +
/ protons, (move) out of companion cells by, active transport / AW ;
R diffuse by active transport
2 H +
/ protons, diffuse (back) in with / cotransport sucrose, into companion cells ;
A description of (facilitated) diffusion
R active transport
ref. to companion cell required only once for mps 1 and 2
3 via, cotransporter / cotransporter described ;
4 sucrose, diffuses / AW, into (phloem) sieve, tube / element, via plasmodesmata ;
5 (entry of sucrose into sieve tube so) water potential lowers ;
6 water enters by osmosis ;
7 (hydrostatic) pressure builds up ; A pressure difference created
8 unloading at, sink / named sink, gives a difference in pressure (between source and
sink) ; AW
9 (so) mass flow ; term to be used in context
Aphids are insects with mouthparts adapted to penetrating the cells of plants which transport assimilates.
Suggest why aphids feed specifically from these cells.
obtain, sucrose / amino acids / other named assimilate ; R nutrients unqualified
pressure forces, sap / AW, into aphid ; [max 1]
The blood vessel that transports deoxygenated blood from the heart.
pulmonary artery
The cell that ingests and digests cell debris and bacteria in the lungs
phagocyte
The cell that secretes antibodies
B-lymphocyte / (effector) B (cell) / plasma (cell)
The epithelial cell that secretes mucus in the trachea
goblet (cell
The tissue that prevents the collapse of the trachea during inhalation.
cartilage
State one role of vacuoles in plant cells.
store of / holds, cell sap ; R if contains organelles
store of / holds, water / ions / named ion(s) / minerals / salts / pigments / (named) sugars ;
R substances / molecules
R storage unqualified
pushes chloroplast to edge of cell ;
gives, turgidity / turgor pressure / hydrostatic pressure / support / AW ;
A makes, firm / rigid
A controls / maintains, turgidity
Explain how the composition of the cell surface membrane determines the permeability
of the cell surface membrane
1 F partially permeable A selectively permeable
and G (fully / freely / AW), permeable / porous ;
F is partially permeable cell surface membrane
2 phospholipid (bilayer);
3 permeable to, lipid-soluble molecules / oxygen ;
A other terms for lipid-soluble
treat reference to water as neutral
4 impermeable to, water-soluble / AW, molecules / ions / AW ;
A other terms for water-soluble
treat reference to water as neutral
5 aquaporins / proteins, provide (increased) permeability to water ;
6 transport proteins provide permeability to, ions / polar molecules ;
A channel / pore / carrier, proteins
Explain how the composition of the permeable cell wall determines the permeability
of the cell surface membrane
G is permeable cell wall 7 cellulose ; 8 fibres ; 9 ref. to, spaces / gaps / holes / pores, (between, fibres / other cell wall components) ;
Describe the roles of plasmodesmata in transport in plants.
allows transport of, water / sucrose / amino acids / organic substances / ions /minerals /
salts / lipids / hormones / ATP, (from cell to cell / between cells) ;
R if linked to an incorrect transport mechanism e.g. sucrose moves by osmosis
2 without crossing, membranes / walls ; A without going through protein channels
3 this is movement through the symplast ;
4 any e.g. ; companion cell to (phloem) sieve tube (element / cell)
between mesophyll cells
mesophyll cell to companion cell
cortical cell to cortical cell / across cells of the cortex
cortical cell to endodermal cell
endodermal cell to, pericycle cell / xylem / phloem
ignore between sieve tube elements
5 allows, communication / signalling, between cells ;
Explain the advantage of the position of the dissociation curve for people with sickle cell
anaemia.
at partial pressures in the tissues ; where oxygen is unloaded from Hb
2 haemoglobin is less saturated (than L) ;
3 because, haemoglobin / Hb, dissociates more readily ;
A idea of unloading oxygen more readily even if Hb not mentioned
4 to compensate for, fewer / less effective, red blood cells / Hb ;
Describe and explain how humans become adapted to the low partial pressure of
oxygen at high altitude
haemoglobin less well saturated (in lungs at high altitude) ;
2 data quote from Fig. 3.1 ; A 80–90% saturated at ‘about 7.5 kPa’
3 produce more red blood cells / increase in number of RBCs ;
4 more haemoglobin ;
5 idea of compensates for, smaller volume of oxygen absorbed / lower saturation (of
haemoglobin) ;
also accept the following adaptations
6 increase in haematocrit / AW / decrease in plasma volume ;
A increase in RBCs per unit volume
R decrease in blood volume
7 increase in, breathing rate / tidal volume / heart rate / stroke volume ;
8 increase in, capillary density / number of mitochondria / myoglobin / respiratory
enzymes, in muscle ;
9 ref. to (increased) secretion of, erythropoietin / EPO ;
10 increase in (2,3), BPG / DPG, in red blood cells ; A rightward shift in curve
Explain why vaccination cannot be used to prevent sickle cell anaemia
not caused by (named type of) pathogen / non-infectious / non-transmissible / noncommunicable
/ AW ;
2 genetic / inherited / AW, disease ; A caused by a mutation / AW
A ‘passed down from parent(s)’
R idea of congenital diseases
R ‘you get it from your mother’
3 ref. to, no immune response / no antigen(s) ;
4 affects all red blood cells so vaccine would lead to their destruction ;
Explain how capillaries are adapted for their function as exchange vessels.
1 (capillary) wall is, thin/ single layer of cells / one cell thick ;
A endothelium/ epithelium for wall
2 short diffusion, pathway / distance/AW ;
R ‘easy’ diffusion
3 (many have) endothelial pores / fenestrations / gaps / spaces / openings ;
4 to allow named, substance/ cell, to leave the blood ;
A idea of separation/ selection, of named substance(s) by size
5 small diameter/ small lumen/ diameter of red blood cells ;
6 slows down flow of red blood cells /(capillary / blood) close to cells ;
7 (capillaries have) large, surface area/ surface area to volume ratio ;
8 idea that allows more exchange ;
Explain the differences between the composition of blood, tissue fluid and lymph for white blood cells
te blood cells
1 (named) white blood cells can, leave capillaries / enter tissue fluid ;
A diapedesis /(suggestion that some) too large to leave the, blood/ capillaries
2 high number in, lymph nodes / thymus / bone marrow/ spleen ;
A stored/ produced
Explain the differences between the composition of blood, tissue fluid and lymph for glucose
small (molecule) ;
4 filtered/ diffuses /leaves / leaks, from blood/ from capillaries / into tissue fluid ;
5 taken up/ used, by cells in respiration ;
Explain the differences between the composition of blood, tissue fluid and lymph for protein
too large to, leave capillaries / enter lymph/ enter tissue fluid ;
7 (in lymph / tissue fluid) antibodies / proteins, from/ secreted by, lymphocytes / other
cells ;
Outline how red blood cells are involved in the transport of carbon dioxide
carbon dioxide, reacts / combines, with (terminal amine/N terminal, of) haemoglobin ; R carried by /reacts with, haem 2 to form carbaminohaemoglobin ; 3 carbonic anhydrase catalyses, formation of carbonic acid (H2CO3)/reverse reaction described (in the lungs) ; 4 (carbonic acid dissociates to) HCO3 – /CHO3 – / hydrogen carbonate (and H+ ) ; 5 hydrogen carbonate/HCO3 – , diffuses /moves /AW, out (into plasma) ;
Transpiration is often described as an ‘inevitable consequence of gas exchange in
plants’.
Explain what is meant by this statement.
stomata open(ings) to allow carbon dioxide in ;
carbon dioxide required for photosynthesis ;
water vapour diffuses out through stomata ;
Describe three ways, other than small size, in which leaves are adapted to reduce the
rate of transpiration.
stomata close (for longer), during the day /when hot/when dry ;
2 stomata in pits / sunken stomata ;
3 stomata only on lower surface of the leaf ;
4 hairs / trichomes ;
5 low number of/ few(er)/ less, stomata (per unit area) ;
ignore ‘less open stomata’
6 thick(er) cuticle;
7 reflective cuticle (on upper epidermis) ;
8 thick(er) epidermis / more than one layer of epidermal cells ;
9 curled/rolled/AW, leaves ;
) Aquaporins are membrane channel proteins in plant and animal cells. They permit the
movement of water across membranes. Explain why they are necessary
water molecules are polar
idea that few polar molecules pass through the phospholipid (bilayer) ;
ora for non-polar molecules
A none pass /repelled
3 core of membrane/ phospholipid tails, are hydrophobic ;
A hydrophobic core
4 channels (through aquaporins), are hydrophilic ;
A core of channel proteins /described as R-groups of amino acids
5 (aquaporins) increase permeability of membrane to water ;
6 example ;
e.g. root hairs / small intestine epithelium/ nephron
7 role of water in a cell ;
e.g. solvent/reactant/reaction medium/ turgidity or support in plant cell
State three structural features that are present in a mesophyll cell in a leaf that are not
present in a prokaryotic cell
chloroplast ; A grana/ thylakoid(s) A plastid
(permanent) vacuole/tonoplast ; R vesicles unqualified A lysosome
mitochondrion/mitochondria ; A cristae
Golgi (body / apparatus / complex)/ dictyosome ; A Golgi vesicle(s)
rough endoplasmic reticulum/rough (ER)/RER ;
smooth endoplasmic reticulum/ smooth ER/SER ; A endoplasmic reticulum, if RER and SER
not given
nucleolus ;
linear/AW, chromosomes ; A DNA + histones
cellulose cell wall ;
starch grain/ amyloplast ;
plasmodesma(ta) ;
larger/ 80S/ 22nm, ribosomes ;
Ascorbase is a drug used in the treatment of type 2 diabetes. Molecules of ascorbase have a
very similar shape to that of the substrate for maltase.
(i) Explain how ascorbase acts to inhibit these membrane-bound enzymes.
maltase and maltose must be correctly referenced
ignore references to reversible/irreversible
(ascorbase) binds to/ fits into/ enters active site ;
complementary (shape) to active site ;
so substrate/ maltose, cannot enter/ cannot bind ;
A no/few, ES complex
A prevents formation of ES complexes
A ascorbase forms enzyme inhibitor complex
competes with substrate / competitive inhibition ;
slows the (rate of), digestion/ hydrolysis / breakdown, of maltose ;
R ‘stops the reaction’
R if in context of starch
alternative answer if candidates assume ascorbase is an enzyme:
ascorbase, breaks down/ digests / hydrolyses, maltase ;
A ascorbase destroys the active site of maltase
so no enzymes to digests maltose ;
slows / stops, reaction/digestion/hydrolysis / breakdown, of maltose ;
Ascorbase is a drug used in the treatment of type 2 diabetes. Molecules of ascorbase have a
very similar shape to that of the substrate for maltase.
Suggest why ascorbase can be used to treat people who have type 2 diabetes
inhibits / slows down/ prevents, breakdown/(catalysing) hydrolysis / digestion, of maltose
(to glucose) ; I starch
less glucose is absorbed/ passes across membranes /enters blood ;
, state three ways in which the lining of
the trachea, bronchus and bronchioles provides protection against the entry of bacterial
pathogens.
cilia beat to move mucus (up the bronchiole/ towards the mouth/ away
from the lungs /AW) ;
mucus as a barrier to entry into (epithelial) cells ;
mucus traps, pathogens / bacteria/ microbes ; accept in context of goblet cells
capillary / blood vessel, brings, phagocytes / macrophages (to engulf
bacteria) ;
(a) Suggest the advantage of complex plasmodesmata between cells in leaves.
) increased/faster, movement/ diffusion, of, assimilates / amino acids /
sucrose/water/ solutes / ions / molecules ;
I substances / particles / carbohydrates
I freely / easily / efficiently
I osmosis
(because) more, (symplast) pathways / passages /AW ;
accept in context of blockage of some plasmodesmata
correct ref. to symplast pathway in context of an advantage ;
e.g. of complex plasmodesmata ;
from companion cell into sieve tube (elements)/when loading sucrose
into phloem
AVP ; e.g. selectivity / control/regulation, of movement
Explain how assimilates in phloem sieve tubes move from the veins in a mature leaf to sinks,
such as flowers and fruits, in the rest of the plant.
mass flow ; A pressure flow
2 sucrose/ solutes / assimilates / sugars, decreases, water potential/
solute potential ; A symbol(s) Ψ
3 water enters (sieve tubes), down water potential gradient/ by osmosis ;
4 increase in/ high(er), hydrostatic pressure ;
5 unloading/removal, of sucrose at the sink lowers the (hydrostatic)
pressure ;
6 movement (from source to sink) is by gradient in (hydrostatic) pressure ;
explain the difference between the two ways in which enzymes interact with their substrates. the lock and key model and the induced fit model
enzyme A uses ‘lock and key’ and enzyme B uses induced fit ;
A enzymes work by ‘lock and key’ and induced fit
enzyme A/ lock and key, (shape of) active site is complementary /AW, to
(shape of) substrate (molecule) ;
enzyme B/ induced fit, has an active site that, moulds around/ AW, the
substrate ;
) Smooth muscle in the trachea and in the bronchi relaxes during strenuous exercise.
Suggest the advantages of relaxing this smooth muscle during periods of strenuous exercise.
more air/ oxygen, reaches the, alveoli/ gas exchange surface ;
2 more gas exchange/greater absorption of oxygen/ excretes more carbon
dioxide ; AW
A maximises oxygen obtained
3 satisfies increased demand for oxygen/AW ;
4 trachea/ bronchi/ airways, widen/AW ;
e.g. dilate/expand/ enlarge A diameter of lumen increases
5 reduces resistance to air flow ; R rate of air flow increases
Explain how hydrogen bonding is involved in the movement of water in the xylem
adhesion of water to, cellulose/ lining/walls (of xylem vessels) ;
A adhesive force
2 ref to, hydrophilic / polar, property of cellulose (fibres) ;
A hydrophilic / polar, parts of lignin
3 cohesion between water molecules ; cohesive force
4 maintains column of water/ prevents water column breaking/AW ;
5 ref. to transpiration pull/AW ; I transpiration unqualified
Outline the changes that occur as cell X becomes a mature red blood cell
produces /makes / synthesises, haemoglobin ; I fills up
2 produces /makes / synthesises, carbonic anhydrase ; I fills up
3 loss /AW, of the nucleus ;
4 loss /AW, of (named) organelles ;
e.g. ribosomes /(R)ER/ mitochondria
5 becomes biconcave/described ;
6 AVP ; e.g. cell surface/ antigens / named antigens
ref. to cytoskeleton
Explain why it is necessary for the athletes to increase the concentration of haemoglobin
in their blood when acclimatising to high altitude.
low(er) partial pressure of oxygen (at high altitude) ;
A pO2 / ppO2
2 less oxygen in, inhaled air/ lungs / alveoli ;
3 so haemoglobin, is not fully saturated/has lower saturation (with
oxygen) (than at sea level)/ lower affinity for oxygen ;
4 idea that more red blood cells so, higher concentration of/ more
haemoglobin ;
5 allows, same/ similar/ enough, volume of oxygen to be transported in the
blood as at sea level ;
6 volume of oxygen transported in the blood is less ;
7 less oxygen for (aerobic) respiration/ lack leads to anaerobic
respiration ;
8 any consequence, e.g. fatigue, altitude sickness ;
Name two smoking-related diseases associated with COPD.
emphysema ;
chronic bronchitis ;
w the pathway that air takes during inhalation.
nasal cavity pharynx larynx trachea/windpipe bronchus /bronchi bronchiole/ bronchioles alveolus / alveoli
active transport
transport mechanism across cell
surface membrane and
example of material transported across membrane
sodium ions
transport mechanism across cell
surface membrane
passive diffusion
and
example of material transported across membrane
oxygen molecules
endocytiosis
transport mechanism across cell
surface membrane and
example of material transported across membrane
bacteria
exocyosis
transport mechanism across cell
surface membrane and
example of material transported across membrane
mucin (for mucus)
With reference to the structure of a leaf, explain the difference between evaporation and
transpiration.
max 3 if no attempt at comparison
evaporation
1 formation of water vapour from water / conversion of water from liquid (form) to gas(eous
form) ;
2 requires, energy / heat ;
3 (water loss) from, surface / cell walls, of (spongy) mesophyll (cells);
transpiration
4 idea of loss of water vapour, to external atmosphere / from the aerial parts of a plant ;
A from leaves
5 ref. diffusion, down water potential gradient / from high to low water potential / from less
negative to more negative water potential ; A Ψ for water potential
6 through stomata ;
air spaces
7 correct ref. to, intercellular / air, spaces ; e.g. evaporation into air spaces, diffusion from
air spaces through stomata
Describe how the transpiration rate during the night would differ from the
transpiration rate during the day.
Explain your answer.
(ii) decreased / lower, rate during night ; ora
stomata closed at night ; ora
further detail ; e.g. closed to prevent water loss
closed as no photosynthesis
no light for photosynthesis
open (during day) for, gas exchange / CO2 in
Suggest how increasing phosphate ion uptake will lead to increased plant growth.
idea of, increase in cell numbers / more cells ; A ref. to mitosis / cell division
2 ATP, qualified ; e.g. for, cell growth / anabolic reactions
3 (activated) nucleotides for, DNA / RNA, synthesis ;
4 phospholipid for membranes ;
5 DNA replication (for cell division) ;
6 RNA for, protein synthesis / AW ;
7 AVP ; e.g. activate glucose for glycolysis
ref. NADP, light-dependent reaction
Describe and explain how the structure of xylem vessels is suited to their function.
transport of water and mineral ions ; A minerals
2 elongated cells / cells end to end
(to form)
tubes for transport ; A (e)long(ated) tubes for transport
3 no, end / cross, walls or end / cross, walls broken down
so
minimal resistance to / unimpeded / free, flow of water ; AW
4 hollow / no cytoplasm / no contents / no organelles / empty, ignore dead
so
more space for greater volume to flow / greater volume per unit
or
minimal resistance to / unimpeded / free, flow of water ; AW
5 cellulose lining A cellulose walls
so
hydrophilic / adhesion of water molecules / for movement of water up stem / to
maintain column of water / AW ;
A hydrophilic lining, for movement of water up stem / to maintain column of water
6 lignified (walls) / walls contain(s) lignin A thickened walls
R lined with lignin
so
prevents (inward) collapse / withstands negative pressure
R prevents bursting
7 lignified (walls) / walls contain(s) lignin A thickened walls
R lined with lignin
so
waterproof / prevents loss of water / prevents leakage / maintains column
8 additional ref. to lignin ; e.g. for support of plant
spiral / annular, thickening allows elongation (of stem)
for support of plant
9 pits / pitted walls
to
allow, sideways / lateral, movement (of water)
or to connect to all parts of plant / AW ;
10 relevant ref. to diameter of lumen ; e.g. narrow, for adhesion R capillarity
(relatively) wide to transport maximum volume of water
Outline the differences between the apoplast and symplast pathways after the water has left
the xylem.
apoplast = cell wall (and intercellular spaces) (pathway) ;
A between cell walls
R if cell wall and, cytoplasm/ vacuole/ plasmodesmata
R if linked to osmosis / facilitated diffusion/ active transport
2 symplast = cytoplasmic (pathway) ; R if facilitated diffusion/ active transport
reference to only cytoplasmic / not including vacuoles
mps 1 and 2 allow one mark only if no ref. to terms apoplast and symplast
e.g.cell wall v cytoplasmic pathway
symplast
3 osmosis, linked to passage across membranes ; must be in correct context
4 detail of membranes involved ; either tonoplast/ vacuolar membrane or cell
(surface) membrane of, ‘first cell’ entered directly from xylem/AW
5 via plasmodesmata ; ignore ref. to mechanism
6 (includes) vacuolar pathway /(through) vacuoles ;
apoplast
7 non-living pathway ; ora
8 ref. greater volume/ higher rate/ less resistance/AW ; ora
A faster/ fastest R amount for volume
9 ref. to, hydrogen bonding/ adhesion, to cell walls ;
State two ways that water is used in the leaf cell.
(maintain) turgor/ turgidity /prevents flaccidity / prevents plasmolysis ;
A provides support for cell R provides support for plant
A pushes chloroplast to edge (of cell)
(reactant in) photosynthesis ;
hydrolysis (reactions) ; A named reaction that involves hydrolysis solvent
A (medium) for cell,/ metabolic / chemical, reactions (to take place)
R if in context of outside cell or entering cell or as a transport medium
Suggest why a decrease in the volume of plasma in the blood may reduce the effects of
hypoxia
greater concentration of/(proportionately) more/AW, red blood cells
(through pulmonary capillaries per unit time)/AW ;
A haemoglobin for red blood cells
increases, the haematocrit/ the percentage of red blood cells to the total
blood volume/AW ;
When a person travels from 0 m (sea level) to a high altitude, gas exchange in the lungs is
affected. A condition known as hypoxia results, where the body tissues do not receive an
adequate oxygen supply.
Explain how hypoxia occurs when a person ascends from sea level to a high altitude
lower, atmospheric pressure/ partial pressure of oxygen so
lower partial pressure of/ less /AW, oxygen in, alveolar/ inspired/ inhaled, air;
A breathed in for inspired
A less oxygen goes into lungs
decreased, diffusion/ concentration/ pressure, gradient ;
between, alveolus / alveoli, and capillary ;
less /AW, oxygen, enters /AW (pulmonary) capillaries / the blood ;
A less /AW, oxygen, transported/AW, by, haemoglobin/red blood cells / blood
(to tissues)
(so) percentage saturation of haemoglobin is lower ;
A haemoglobin is less saturated
A fewer molecules of/ less, oxygen combine with haemoglobin
(as) haemoglobin has lower affinity (for oxygen than at sea level) ; AW
A ref. to effect of 2,3 DPG
allow correct explanation in terms of oxygen dissociation curve
ref. to insufficient red blood cells to compensate ;
ora e.g. more red blood cells, need to be/will be, produced
describe the effect of increasing altitude on both atmospheric pressure and the partial
pressure of oxygen
(as altitude increases), both of them/ atmospheric pressure and oxygen
partial pressure, decrease ;
(one) correct comparative data quote ;
altitude and pressure, with units once, for either atmospheric pressure
or oxygen partial pressure
non-linear decrease ; A almost linear decrease
decrease in oxygen partial pressure proportionate to decrease in
atmospheric pressure ;
Explain why an increase in the heart rate occurs in response to hypoxia.
more, blood/red blood cells, flowing to lungs (per unit time) ;
A blood flows faster to lungs
to maximise oxygen uptake (from alveoli)/ takes in more oxygen/AW
/ compensates for lack of oxygen ;
more blood pumped through, systemic circulation (per unit time)/rest of
body /to tissues /AW ; A blood flows faster for more blood
compensates for the lowered plasma volume
or
ref. need to, maintain supplies of required substances /remove waste/
prevent decrease in pH ;
allow named required substances e.g. glucose/oxygen/ amino acids
allow named waste substances e.g. carbon dioxide
(a) Explain the need for transport systems in multicellular plants and animals.
small / AW, surface area to volume ratio / SA:V (compared to unicellular) ;
ora large volume to surface area
A as organisms increase in size, surface area to volume ratio / SA:V, decreases
ref. long(er) distances (to reach cells / tissues) ;
A transport system reduces diffusion distance (as it takes materials close to cells)
diffusion (alone), too slow / insufficient / unable to satisfy needs / AW ;
A transport system decreases time to supply cells
ignore ref. to named substances diffusing
ref. efficient / AW, supply (to cells) of, glucose / amino acids / dissolved food ;
/ nutrients / hormones ;
A idea of greater volume (containing required materials) or higher concentration of materials
R oxygen, unless only transport in mammals
ref. xylem, phloem, circulatory system ; must have all three
A arteries and veins / blood transport system / blood vessels
The chamber that pumps blood into the pulmonary artery.
right ventricle ;
A blood vessel that transports deoxygenated blood into the right atrium.
vena cava
The specialised tissue responsible for delaying the conduction of impulses from the atria to
the ventricles.
atrioventricular node
The blood vessels that supply cardiac muscle with oxygenated blood.
coronary arteries
The valve that prevents the backflow of blood from the ventricle that contains oxygenated
blood.
bicuspid
Goblet cells produce mucus. Name one other structure in the gas exchange system that also
produces mucus.
mucous gland
explain one feature that enables the surrounding body cells to
receive an adequate supply of oxygen from the blood supplied by the capillary
F red blood cells / haemoglobin, close to body cells ;
F (capillary) endothelium/ capillary wall, one cell thick / thin ; A epithelium
E short distance/AW (for oxygen to move to cells) ;
F ref. to, diameter/ size, red blood cell and capillary (lumen) similar ;
E slows down flow (to allow sufficient oxygen to move out)/ short distance
(for oxygen to move to cells) ;
Some areas of the brain, known as blood-brain barriers, have a type of capillary that is
relatively impermeable to substances.
Suggest one way in which the structure of a capillary in the blood-brain barrier differs from
the structure of the other capillaries
) no/ fewer, gaps /fenestrations / pores, in endothelium/ capillary wall ;
A spaces
ref. tight junctions between (endothelial) cells ; A epithelial cells
idea that cells wrap round/ fewer cells make up capillary wall, so reduces
(endothelial) cell-cell contact ;
idea of layer around capillary / basement membrane, impermeable ;
a plant adaptation of your choice reduces water loss.
allow explanations for stomata in pits, thick cuticle and no stomata on outer
surface as ecf from (i)
curled leaf/ trichomes / stomata in pits
ref. to (creates) still/ non-moving, air ;
(in enclosed area) humid/ moist ; AW, e.g. traps water vapour/ maintains
humidity
water potential gradient less steep or decreased rate of diffusion of water
vapour (out) ;
A (water) vapour pressure gradient for water potential gradient
I decreased concentration gradient of water vapour
assume in context of between substomatal air space and enclosed area
unless stated otherwise
thick cuticle
greater layer impermeable wax /AW ; A thicker waterproof layer
increases distance for diffusion ;
of water vapour ;
no stomata on outer surface
most water lost via (open) stomata ;
cuticular transpiration only ;
ref. to where most exposure to, light/air currents /wind ;
Explain what is meant by a closed double circulation.
blood contained in (blood) vessels AW
or
blood contained in any three of
heart, arteries, veins, capillaries ;
systemic and pulmonary, systems / circulation ; A ‘systematic’
A described if circulations not named
e.g. for each complete circuit (round the body) passes through heart twice
from heart to lungs and back, then to (rest of) body and back
Describe the process of gas exchange between the alveolus and the blood.
idea of carbon dioxide out (of blood to alveolus) and oxygen in (to alveolus
from blood) ;
2 diffusion/ diffuses
or
(movement from) high concentration to low concentration/ down a
concentration gradient ; A diffusion/ pressure, gradient
3 (across) squamous epithelium/ squamous cells (of alveolar wall) ;
A pavement cells
4 (and) endothelium/ endothelial cells (of capillary wall) ;
A squamous cells but must be clear that this is for capillary wall
5 oxygen, into / AW, red blood cells ; I oxygen binds to Hb
6 steep gradient maintained by, ventilation/ uptake by haemoglobin/ blood
carries oxygen away / blood arrives with carbon dioxide/ deoxygenated
blood arriving low in oxygen
Explain why the rate of water uptake by the leafy part of the plant
not be the same as the rate of transpiration.
b) idea that water taken up may not all be lost in transpiration / transpiration is water loss (as water vapour) from (aerial parts / leaves, of) the plant ; example of use of water taken up ;; e.g. photosynthesis hydrolysis reactions maintaining turgidity / AW cell, elongation / increase in size
ref. to water uptake rate and transpiration rate differing because of (changing) environmental
conditions ; A examples e.g. higher transpiration rate than uptake rate in hot and dry
external conditions
Explain the effect of increasing the temperature on the rate of water uptake of plants
if no mp 1 and 2, accept increased rate of transpiration for one mark
1 increased rate of evaporation ; A description of evaporation
R evaporation, from leaf / from stomata / through stomata
2 increased rate of diffusion ; in context of water vapour out through stomata
3 (rise in temperature), lowers (relative) humidity / decreases water potential of air
(outside leaf) ;
4, 5 AVP ;; e.g. increased kinetic energy
steeper water potential gradient established in correct context
details of cohesion-tension theory linked to increased, transpiration / water uptake,
rate
increased rate of photosynthesis
replacing water lost from cells in leaf
State two environmental conditions, other than temperature, which will affect the
rate of water uptake of a leafy twig
humidity ;
wind (speed) ; A air movements
light intensity ;
(air) pressure ;
Due to the movement of ions into the lumen, water moves from the epithelial cells
into the lumen.
Name the process by which water moves and explain why it moves into the lumen.
osmosis ;
increasing, ion / solute, concentration in lumen (of intestine) lowers water potential ; ora
water follows, from a high(er) to a low(er) water potential / down a water potential
gradient;
Explain how water moves from the xylem in the leaf into these vacuoles.
ref. to movement, down water potential gradient/from high(er) to low(er) ;
2 apoplastic / cell wall, pathway from xylem to cell walls of (palisade mesophyll) cells ;
3 ref. to osmosis ; in context of movement, into cell / through cell surface
membrane/ through tonoplast,
R osmosis from xylem to vacuole
4 symplastic / cytoplasmic, pathway (within cell) ;
5 via plasmodesmata ; in context of water arriving from adjacent cell
6 ref. to channel proteins / aquaporins ;
7 solutes / named, in vacuole ;
Explain why lung cancer is sometimes referred to as a ‘lifestyle disease’
causes (mainly) linked to habits during life of person/AW ;
result of choices made by person/AW ;
example ;
e.g. (tobacco) smoking/ exposure to asbestos at work
List three adaptations, visible which are characteristic of xerophytic plants.
stomata in, pits / cavities / chambers / crypts ; I sunken stomata
no stomata on upper surface ;
few stomata ;
hairs / trichomes ;
thick (waxy) cuticle ;
thick walled epidermal cells ;
several layers of, upper epidermis / hypodermis ;
Describe the process of transpiration in plants such.
1 loss of water vapour from, leaves / aerial parts of the plant ;
2 water evaporates from, walls / surface, of mesophyll cells ;
3 into air spaces ;
4 water vapour diffuses(out to atmosphere) ; A water if mp2 awarded
5 through open stomata (to atmosphere) ;
6 down a water potential gradient ;
A idea that water potential gradient established
) Explain what causes oxyhaemoglobin to dissociate readily in actively respiring tissues
accept Hb for haemoglobin throughout
low(er), partial pressure/AW, of oxygen /O2 ;
high(er), partial pressure/AW, of, carbon dioxide/CO2 ;
formation of carbaminohaemoglobin ;
carbonic acid disocciation to form, hydrogen ions /H+
(and hydrogen carbonate
ions) ;
formation of haemoglobinic acid/binding (of Hb) with, hydrogen ions /H+
, causes
release of oxygen ; allow HHb
ref. to Hb affinity for oxygen ; e.g.
Hb has higher affinity for, hydrogen ions /H+
, than oxygen ;
reduces / lowers, affinity of Hb for oxygen
Bohr effect ;
AVP ; e.g. ref. to allosteric effects
State one way in which nicotine in tobacco smoke affects arteries.
damage/AW, to, endothelium/ tunica intima/AW ;
promotes blood clotting/ makes platelets sticky / increases risk of
thrombosis /AW ;
(so) contributes to plaque/atheroma ; A atherosclerosis
ref. (vaso) constriction ; A reduces diameter
A reduces resistance to blood flow
how does a smokers artety look comapred to a non smoker
deposit/ build-up/ presence/AW, of atheroma /(atheromatous) plaque ;
thicker wall ;
narrowing of the lumen ; R lumen, blocked/ clogged
lumen no longer round ;
rougher/AW, lining ; A idea of damaged endothelium
artery:
structural feature
function
one correct structural feature with one relevant corresponding function e.g.
thick / muscular, wall ; A thick tunica media A smooth muscle
withstand high blood pressure/ maintains pressure/ provides strength ;
elastic tissue ;
provide, stretch/recoil/AW ;
smooth tunica intima ;
maintain, laminar/ smooth, flow ; AW
presence of collagen ;
prevents rupture/AW ;
allow the function mark for general statement
transports blood away from the heart to the (lungs and) rest of the body ;
capillary:
structural feature
function
one cell thick (wall)/ endothelium only /thin wall/AW ;
short diffusion distance/ high rate of diffusion ; I easy diffusion
pores / gaps / spaces, between, cells in wall/ endothelium ;
to allow exchange of substances /example described/ formation of tissue
fluid ;
small, diameter/ cross sectional area ; A range 7–12µm
ref. efficient, exchange/ delivery / collection, of materials ;
e.g. reaches all cells /AW
slows down blood flow
maximises time for red blood cells to collect/ deliver, oxygen
reduces distance for diffusion to cells
Explain how the structure of veins is related to their function in returning blood to the
heart.
(ii) (presence of) valves ; R bicuspid/ tricuspid, valves
to stop backflow/ allows one-way flow/ flow only towards heart ;
Explain why multicellular organisms require transport systems while unicellular organisms,
such as Chlamydomonas, do not.
assume multicellular organisms unless stated, then accept ora
1 small, surface area to volume ratio/SA:V ;
A as organisms increase in size, SA:V decreases
2 ref. to (larger size means) long distances (to reach, cells / tissues) ;
3 diffusion, too slow/ insufficient/ unable to satisfy needs ;
4 transport system decreases time to supply cells ;
5 require, bulk / mass, flow ;
6 ref. to transport system means efficient supply (to cells) of nutrients
Describe the appearance of the lining of the bronchus in a long-term smoker.
presence of any 3 of:
1 shorter/ no/ fewer/ damaged, cilia ; A paralysed
2 undifferentiated/AW, cells ;
3 flattened/ squamous, cells / epithelium ;
4 scar tissue ; A scar tissue forms
5 enlarged goblet cells ;
6 excess / accumulated/AW, mucus ; A excess mucus secreted
7 tar deposits ; A description of tar on lining
8 phagocytes ;
9 AVP ; e.g. inflammation (of bronchial lining)
Describe the function of phloem sieve tubes.
transport of assimilates ; A named assimilate e.g. sucrose/ amino acids / auxins
from source to sink ; A from leaves to named sink e.g. roots / fruits
translocation/ mass flow ;
Explain how the structure of the walls of xylem vessel elements are adapted to their functions.
gnin for, waterproofing ;
lignin, for support/ to prevent (inward) collapse/AW (of vessel or plant) ;
R prevent bursting I withstand (high) pressure
cellulose for, adhesion of water/ formation of hydrogen bonds with water ;
A hydrophilic parts of lignin
pits for lateral movement of water ;
AVP e.g. rings / spirals, for, extension/ growth ;
Describe the pathways taken by water as it moves from the soil into the xylem of the root.
treat refs to mechanisms as neutral (soil to) root hair ; idea of across, cortex / cortical cells (root) ; apoplast / along cell walls ; symplast / via, cytoplasm / plasmodesmata ; through, endodermis / endodermal cells, by symplast pathway ; (because of) suberin / Casparian strip ; ref to passage cells ; apoplast into the xylem
Suggest one role for the pre-capillary sphincter muscle
vasoconstriction / contract / constrict / close / narrow, to, stop / control / reduce, blood flowing through capillaries ; blood, diverted / shunted, elsewhere ; any suitable e.g. ; diverted from, skin when cold / gut during exercise
vasodilation / relax / dilate / open / widen, to allow blood to flow through capillaries ; blood required in tissue to deliver, oxygen / glucose or to remove, lactate / carbon dioxide
Explain why the wall of the artery is thicker than the wall of the vein
withstands high(er) blood pressure ; maintains blood pressure ; ref to more, elastin / collagen / (smooth) muscle ; A thicker muscle
describe the role of capillaries in forming tissue fluid.
pores / gaps / perforations, in / between, (endothelial) cells ; A pores in capillary wall R spaces, holes water / ions / glucose, move out ; A named small soluble substances R list which contains incorrect substance / red blood cells hydrostatic pressure of blood is greater than (hydrostatic) pressure of tissue fluid ; (causing) pressure filtration / AW e.g. forced out under pressure / ultrafiltration ; R leaking pinocytosis across capillary wall
Describe three ways in which plasma differs from tissue fluid.
any three of the following more / plasma, proteins ; more glucose ; R sugars more, fat / fatty acids / glycerol ; lower, water / solute, potential ; R water concentration lower carbon dioxide concentration / lower concentration of HCO3- ; higher oxygen concentration ; AVP ; e.g. cell secretes substance that is in higher concentration in tissue fluid, another named solute, higher pressure
Describe the function of elastin in the lungs
expands / stretches, during inhalation ; recoils during exhalation ; forces air out of alveoli ; prevents bursting of alveoli
Describe how companion cells load sucrose into phloem sieve tubes
+ pumped out ; creates an H+ gradient ; sucrose moves in with H+ co-transport / through co-transporter ; energy / ATP, provided by mitochondria ; sucrose diffuses down concentration gradient ; through plasmodesmata ;
Phloem transfer cells are specialised companion cells that load sucrose into sieve tube elements.
Transfer cells move large quantities of sucrose into phloem sieve tubes.
Suggest why these cells have cell wall ingrowths
Describe the appearance of the phloem sieve tubes when viewed in longitudinal section
long (length greater than width) ; sieve plates ; sieve pores ; some / less / peripheral, cytoplasm ; no nucleus / fewer mitochondria / less ER ; thin wall ;
Explain what is meant by the term transpiration
loss of water vapour ; from leaves / aerial parts of plant ; R stomata unqualified ignore evaporation
Explain how the physiologist would determine the vital capacity of the athlete
athlete takes a deep breath and then breathes out as much air as possible / AW ;
suitable method to record this, e.g. spirometer / breathing out into a bell jar of water ;
With reference to Fig. 5.1, explain how phloem transfer cells help in the movement of sucrose from the mesophyll of a leaf into a phloem sieve tube element
explanation to max 4
hydrogen ion / H + , pumped / AW, out of, transfer cell / companion cell ;
R if to sieve tube element
active / using ATP / energy requiring ;
hydrogen ion gradient build-up ; AW
hydrogen ions, co-transport / with / AW, sucrose ; in context of into, transfer /
companion cells
diffusion / facilitated diffusion (of hydrogen ions and sucrose) through co-transporter
(membrane protein) ;
A through membrane protein if ‘cotransport’ already used
sucrose, diffuses / AW, through plasmodesmata into sieve tube element ;
ref. to Fig. 5.1 mitochondria for ATP production ; ref to infoldings of cell wall ; large surface area of cell membrane ; for more, protein pumps / co-transporter proteins ;
Explain how sucrose in the phloem sap is moved from sieve tube elements in leaves to cells in a sink, such as a root.
sucrose / assimilates / phoem sap, in sieve tube (elements) in, source / leaf
low(ers) / less negative, water potential ;
water enters, qualified ; e.g. by osmosis / from surrounding tissue;
increases the hydrostatic pressure ;
sucrose unloaded at sink ;
lowers water potential in surrounding tissue ;
water moves out and decreases hydrostatic pressure (in source) ; allow ecf if
hydrostatic not used
pressure difference (causes flow) ;
(pressure difference) forces sap through sieve tubes / causes mass flow (towards
sink) ; AW
explain how water is absorbed by root hairs
1 diffusion through (freely permeable) cell wall; 2 membrane is partially permeable ; A selectively 3 osmosis across membrane (into cell) 4 (only) some water may pass between phospholipids (across membrane); 5 movement across membrane facilitated by aquaporins ;
6 ref. down water potential gradient / from high water potential to low water potential; A from a higher / to a lower, water potential if in context 7 AVP ; e.g. further detail about aquaporin (hydrophilic channel)
Describe the pathway taken by water from the cytoplasm of the root hair cell to a xylem vessel in the centre of the root.
pathway via, cells of cortex / cortical cells, and endodermis / endodermal cells ;
symplast pathway, described as cytoplasm and, plasmodesmata / vacuole(s) ;
(out of cell to) apoplast pathway, described as cell wall pathway ;
Casparian strip / suberised cell wall, of endodermis, impermeable to water ; (so) pathway only via, symplast / cytoplasm ;
AVP ; e.g. reference to pericycle reference to passage cells of endodermis vacuolar pathway (unless given in mp 2)
why the rate of transpiration is higher during the day than at night in both groups of plants
rate of transpiration, (almost) always / AW, higher / higher at night, in A / mutant plants ; ora A expressed in terms of water loss at night only cuticular transpiration / no stomatal transpiration ; idea that during day stomatal transpiration same for both ; (so) differences because of less effective cuticle ; comparative data quote ;
Describe how a red blood cell develops from a stem cell.
transcription (of specific genes) ; A reference to gene switching protein / polypeptide, synthesis ; A translation production of haemoglobin ; further detail ; e.g. assembly of quaternary structure (production of) carbonic anhydrase ; loss of, mitochondria / named organelles ; loss of nucleus ; adopts biconcave disc shape
Explain what are meant by the terms closed and double as applied to mammalian circulatory systems
closed blood travels, inside blood vessels
whats the role of the microvilli
increase the surface area for absorption/movement across membrane
Describe the role of goblet cells in the gas exchange system
secrete/make/produce/release mucus ; pathogens/bacteria/viruses/microorganism/dust/AW stick to mucus ; A trapped by mucus idea that pathogens/AW do not reach the cells lining the trachea or the cells lining the bronchi or the alveoli ; prevents pathogens/AW entering the circulatory system ; reduces chances of infection
State two environmental factors that affect the rate of transpiration. Explain how each factor affects the rate of transpiration.
each factor 1 mark, explanation for each factor 1 mark look for ora for explanation
temperature ; I high / low or hot / cold
increased temperature, increased rate as higher rate of, evaporation (from spongy cell surfaces) / diffusion (of water vapour out via stomata) or at very high temperature stomata close so transpiration, stops / slows ;
humidity ; I high / low
one from increased humidity, decreased rate as, less steep water potential gradient / decreased diffusion rate (of water vapour out via stomata) ;
wind (speed) / air movement ; I fast / slow
higher wind speed steeper, water potential gradient / higher diffusion rate (of water vapour out via stomata) / diffusion shells do not build up / wind moves moist air away / AW or at high wind speed the stomata close so transpiration slows ;
water availability ; I high / low reduced water availability causes stomata to close (so reduced rate of diffusion ) or more water available, steeper water potential gradient between roots and leaves ;
light intensity ; I high / low
higher light intensity, increased rate as stomata open more widely A more light (as ecf from stating factor) or at very high light intensity the stomata close so transpiration slows ; A stops
explain how hydrogen bonding is involved in the movement of water through the xylem
cohesion and adhesion ; in correct context transpiration stream / transpiration pull ; A continuous column of water moving up (to leaves) attraction / cohesion, between water molecules ; A water is cohesive A stickiness between water molecules adhesion / AW, of water molecules to lining of xylem (vessels) ; only needs ‘molecules’ once adhesion to / AW, cellulose molecules / hydrophilic parts of lignin
Smoking causes changes to the structure of the lining of the bronchi that make smokers more likely to be infected by bacteria. Describe these changes and explain how this leads to an increased risk of bacterial infection.
changes max 2 fewer / no / damaged / AW, cilia ; A paralysed / destroyed R killed A ciliated (epithelial) cells destroyed scar tissue, develops / replaces ciliated (epithelial) cells / AW ; goblet cells enlarged ;
increased risk max 2 thicker layer / more, mucus traps bacteria ; mucus not removed (by cilia action) so, (trapped) bacteria remain / longer time for bacteria to infect cells / AW ; bacteria multiply / bacterial population growth, in mucus (so increases chance of infection) ;
Haemoglobin binds oxygen in the lungs to form oxyhaemoglobin. Describe what causes oxygen to be released from the oxyhaemoglobin as blood flows through respiring tissues.
four from oxygen used up in (aerobic) respiration (in tissues) ; low(er) / decrease in, partial pressure of oxygen / AW ; allosteric mechanism / described ; small decrease in partial pressure leads to a large dissociation of oxygen ;
ref. to decrease in haemoglobin affinity for oxygen (so oxygen released) ; AW
high(er) CO2, partial pressure / AW ; haemoglobinic acid formation / H+ combines with haemoglobin (causes oxygen release) ; AVP ; e.g. H+ from carbonic acid dissociation A H+ results from action of carbonic anyhydrase to form carbonic acid effects of carbaminohaemoglobin formation
Explain why red blood cells are in blood but not in tissue fluid.
too large to pass through, (endothelial) pores / capillary walls
function of the SAN
SAN to max 2 pacemaker / sets rate of heart beat / responsible for rhythmic contraction ; sends out, impulses / waves of excitation ; initiates / brings about / AW, heart beat / contraction of the heart / atrial contraction / atrial systole ;
Function of the purkyne tissue
Purkyne tissue to max 2 conducts, impulses / waves of excitation, down septum to, ventricles / apex of heart / base of heart ; conducts, impulses / waves of excitation through ventricle walls ; to cause, ventricular contraction / ventricular systole (from base upwards)
When a person starts to smoke cigarettes, one immediate effect is a decrease in the oxygen that is taken up in the lungs.
Explain why this is so.
carbon monoxide (in inhaled smoke) binds to haemoglobin / carboxyhaemoglobin formed ; carbon monoxide competes with oxygen for, haemoglobin binding sites / AW; haemoglobin has a higher affi nity for carbon monoxide than oxygen
Describe the process of oxygen transfer between the alveolus and the blood in the surrounding capillary.
oxygen in(to blood), carbon dioxide out (of blood) ; diffusion / from a high(er) concentration to a low(er) concentration ; through alveolar wall and capillary, endothelium / wall ; oxygen enters red blood cells ; oxygen taken up by haemoglobin ; AW
Explain how water was lost from the leaves of the leafy twig
moist / AW, surface of mesophyll cells ; water evaporates / evaporation ; in correct context from spongy mesophyll cell walls ; into (intercellular) air spaces ; air within leaf is fully saturated ; water vapour diffuses through stomata ; A ‘water’ if evaporated
down water potential gradient / from a high to a low water potential / from less negative to more negative water potential
Explain the mechanism by which water is transported in the xylem of the leafy twig while in the potometer.
cohesion-tension ; cohesion / AW between water molecules ; hydrogen bonds ; accept here or for adhesion once only transpiration pull / water is pulled up the xylem / water in a continuous column ;
ignore negative / hydrostatic pressure
adhesion to (cell) walls ; water molecules ‘stick’ to cellulose / cellulose is hydrophilic ; A lignin (although it is hydrophobic!) [3 max]
Name two tissues found in the wall of the bronchus
smooth / AW, muscle; A smooth muscle cells
cartilage ;
connective tissue ; A elastic, fibres / tissue A collagen fibres
A collagen and elastic fibres A elastin and collagen fibres
mucous gland ; A mucus-secreting cells R goblet cells
Describe the appearance of a section through the wall of a bronchus in a person with
chronic bronchitis.
no / few / damaged / destroyed / AW, cilia / A ; R killed / dead
allow ecf from (a)(i)
2 scar tissue ;
3 fewer / damaged / AW, (columnar) epithelial cells / epithelium ;
A ciliated cells epithelial cells replaced by scar tissue = 2 marks
4 goblet cells, enlarged / AW ;
5 enlarged mucous glands ;
6 more (smooth) muscle ;
7 large numbers of white blood cells ; A macrophages, phagocytes
8 inflammation ; A swelling in context of inflammatory response
Suggest why a person with chronic bronchitis is more likely than a healthy person to
suffer from infectious diseases of the gas exchange system
1 pathogens / AW, enter from, inhalation / external atmosphere / AW ; R germs
2 (sticky) mucus traps pathogens ; AW
3 mucus, accumulates / not swept away (because cilia destroyed) ;
4 pathogens / AW, remain / multiply (in gas exchange system) ;
5 increased time leads to increased opportunity to gain entry into cells / AW ; [max
It is formed in the bone marrow and matures from a monocyte. It contains many
lysosomes with hydrolytic enzymes.
macrophage
It is formed, and matures in, the bone marrow. It contains a lobed nucleus and has
the ability to ingest microorganisms by endocytosis.
neutrophil ;
When activated, it differentiates into a cell that secretes a chemical, which causes
other cells to lyse (burst). It contains a large, spherical nucleus.
T-killer
It is formed as a result of a primary immune response and remains in the body. On
activation, it has the potential to produce antibodies during a secondary immune
response
memory B- lymphocyte
Describe three structural features of the blood vessel shown in Fig. 1.1 that would help
to identify it as a vein and not as an artery.
vein large / wide, lumen (relative to thickness of wall) ;
A artery narrow lumen
2 irregular shape ; AW
A flattened / oval / not round(ed) (shape) ;
A artery, round(ed) / regular (shape)
I ref. to (vein) not spherical / artery spherical
3 thin / AW, tunica media / middle layer / (smooth) muscle and elastic layer
or
(proportionately) less, elastic / (smooth) muscle, in, tunica media / middle layer ;
4 (relatively) thin, tunica externa / tunica adventicia / outer layer / fibrous coat /
fibrous layer ;
R small(er)
5 tunica intima / tunica interna / inner layer / endothelium, smooth / not ‘crinkly’ /
not wavy / AW ;
alt if mp 3 not awarded, award 1 mark only for
thin (smooth) muscle layer / less (smooth) muscle
thin elastic layer / less elastic tissue
Explain how the following structural features of a capillary are related to its function.
(i) The capillary wall is composed of a single layer of squamous epithelial cells.
short distance for diffusion (of molecules / ions / named) ;
A reduced distance / thin / short pathway / AW
increased rate / AW, of diffusion (of molecules / ions / named) ;
A fast(er) / (more) efficient
I easy / better
Explain how the following structural features of a capillary are related to its function.The diameter of the capillary lumen is approximately 8microm
1 small size allows contact with (many body) cells / AW ;
A idea of extending into small spaces
2 red blood cell, close to, (body) cells / tissue for (efficient), diffusion / AW ;
A in contact with / close to, capillary wall / endothelium, for diffusion
3 red blood cells / blood flow, slow(s) down / idea of more time,
for (efficient) diffusion / cells to obtain sufficient nutrients / AW ;
treat ref. to lower pressure as neutral
4 (plasma / blood, containing), glucose / nutrients / named nutrient / oxygen,
close to / AW, body cells ;
Explain the need for transport systems in plants
1 large (size / volume / organism) ;
A multicellular / many cells
A larger
2 (so) small(er) / low, surface area : volume ;
as size increases, SA:V decreases = 2 marks
3 diffusion (alone), not enough / too slow (to supply needs) ;
4 explanation ; e.g. surface too far from, centre / AW, of plant
distances too far to supply required, nutrients / substances
requires, supplies in bulk / mass flow
5 (so require) xylem and phloem, qualified ;
e.g. transport in different directions
xylem transports water (and mineral ions) and phloem transports, assimilates /
photosynthates / sugars / amino acids
explain how the different structures of cell types the sieve tube element and the
are related to their function.
mitochondria for, aerobic respiration / oxidative phosphorylation / ATP,
production / AW ;
R ATP energy
A release / supply, ATP / energy (for the cell)
treat as neutral cell B also has mitochondria
2 RER / many ribosomes, for, polypeptide / protein, production ;
if mps 1 and 2 not given, one mark for mitochondria and, ribosomes / RER
3 ref. nucleus and, genes coding for (required) proteins / synthesis of ribosomes
or
nucleolus synthesises ribosomes ;
cell B / sieve tube element
4 (at least) one main structural feature ;
R hollow
peripheral cytoplasm / AW e.g. pushed against walls
no nucleus / no RER / no vacuole / no Golgi / few organelles /
reduced ER / few mitochondria
R no organelles
5 (to) minimise / reduce, resistance to (mass) flow ; AW
e.g. uninterrupted flow / more efficient transport of sucrose
6 (so) maximum volume transported (/unit time) ;
A idea of
7 sieve plates, qualified ; e.g. stop bulging
allow mass flow / reduce barrier to flow
become plugged with, P-protein / callose, to prevent losses / after damage
8 no plasmodesmata (as on Fig. 3.1) to maintain pressure or plasmodesmata (not shown) for diffusion of sucrose into sieve tube / AW
state four differences between transport systems in mammals
and in plants. Mammals
arteries, veins, capillaries A delivery to cells by arteries and capillaries heart / pump 3 double circulation 4 closed circulation 5 one (circulatory) system / water and6 (all) living cells 7 transports, (respiratory) gases / oxygen / carbon dioxide organic molecules transported in same vessels / AW 9 faster rate of flow 10 rate of flow controlled by, nervous system control of heart / action of heart / vasoconstriction and vasodilation / AW accept ref. endocrine system 11 components include blood cells 8 transports glucose accept within correct list 12 13 14 AVP ;;; homeostasis involved / concentration of dissolved substances controlled ref. to defence e.g. immune system e.g. blood clotting organ-based valves present
state four differences between transport systems in mammals
and in plants.plants
xylem and phloem ;
A vascular bundle no heart / no pump / (xylem and
phloem) have different mechanisms
for (mass) flow ;
A transpiration pull in xylem /
pressure gradients in phloem no double circulation / xylem unidirectional
flow / phloem source to sink /
AW ; R single circulation no double circulation / xylem unidirectional
flow / phloem source to sink /
AW ; R single circulation two (separate) systems / water transport in
separate vessels to organic molecules ; living and dead cells ;
A dead cells in xylemrespiratory gases not transported ; (phloem) transports sucrose ;slower rate of flow ;rate of flow, not controlled by nervous
system / (in xylem) controlled by
external factors / (in xylem) controlled by
transpiration rate ; cells not transported / AW ;no homeostasis / AW ;
no equivalent to immune system
callose formation ;
tissue-based ;
no valves ;
Nicotine has an effect on the cardiovascular system, such as making platelets sticky, so
causing blood to clot. This increases the risk of thrombosis and reduces blood flow.
Outline other effects of nicotine on the cardiovascular system.
increases heart rate ;
A heart, pumps / beats faster
2 increased blood pressure / hypertension ;
3 damage to, endothelial / arterial, lining ;
A damage to, tunica intima / lining of veins
4 (so) contributes to plaque / atheroma ;
A atherosclerosis
5 vasoconstriction
or
constricts / reduces diameter of, arterioles / blood vessels ;
A more resistance to blood flow must be in context
6 reduced blood flow to extremities / AW ;
Describe and explain how water and nitrate ions are transported in the xylem from roots to
leaves
descriptions across the root, e.g. symplastic and apoplastic route
I ref. to hydrostatic pressure
1 nitrates dissolved in water ;
2 in an apoplastic / a non-cytoplasmic route (in xylem) ;
3 passive (transport)/ does not require energy ; describe
4 transpiration pull/ idea of column of water pulled up ;
5 movement of water out of xylem creates tension ; A negative pressure
6 cohesion of water molecules / explanation in terms of
hydrogen bonding ; explain
7 adhesion of water molecules to cellulose/ lining ; I lignin
8 AVP ; e.g. water potential gradient root to leaf
mass flow caused by evaporation
, describe the effect of carbon monoxide on the cardiovascular
system.
1 carbon monoxide binds to Hb/Hb has higher affinity for CO than O2 ;
A carboxyhaemoglobin forms (heavy smoker)
2 (with CO) Hb reaches lower % saturation/lower percentage saturation
(after 3.6–, 4.0–4.2 kPa) ;
A correct figures quoted
R lower saturation at all partial pressures of oxygen
3 less oxygen taken up, in lungs /at higher partial pressures
or
reduces the volume of oxygen transported ; AW
4 below 3.6–4.2 kPa (with CO), curve shifts to left/Hb has (relatively) higher saturation ;
5 less oxygen unloaded at lower partial pressures / in tissues ;
6 heart rate increases to deliver sufficient oxygen ;
7 ref. to insufficient oxygen to heart muscle and effect on people with CHD ;
Explain the circumstances that cause the closing of the semi-lunar valves during the cardiac
cycle
following ventricular systole/ contraction
or
when ventricles in diastole/relaxation ;
when pressure in arteries higher than that of ventricles
or
when pressure in ventricles lower than in arteries ;
A aorta/ pulmonary artery
Explain the differences between the composition of blood and the composition of tissue fluid
at the arterial end of a capillary bed.
in blood
idea that red blood cells too large to leave capillaries ;
idea that (some plasma) proteins too large to leave capillaries ;
higher concentration of oxygen, qualified ;
e.g. from lungs
not yet unloaded (from haemoglobin)
not yet diffused out (from red blood cell)
not yet forced out of capillary (in plasma)
(higher concentration of) glucose/ nutrients / named nutrient, qualified ;
e.g. to be delivered to cells / from absorption
tissue fluid contains
ref. to products excreted by cells (yet to enter blood) ;
e.g. waste products /(more) carbon dioxide/ lactate
Bacteria that enter the stem through a wound can reach the root of the plant to cause damage.
Suggest how the bacteria are able to reach the root of the plant
travels in phloem/ phloem sap/ translocation ; R in xylem
from cell to cell via plasmodesmata ;
in symplast pathway ;
in apoplast pathway ; R in xylem
ref. to bacterial motility, e.g. flagella ;
This is an artery because it has
a thick tunica media ;
a thicker tunica media than tunica externa ; ora
a thick layer of, (smooth) muscle / muscle and elastic tissue ;
A thick muscular wall
R striated / skeletal, muscle
many (layers of) smooth muscle cells ;
a, well-defined / firm / oval /regular/AW, shape (in cross section) ;
narrow/AW, lumen in relation to thickness of wall ; A narrow lumen
convoluted /folded /AW, endothelium / tunica intima ;
function of the AVN
delays, impulse / AW ;
R nerve impulses / signals / messages / waves unqualified
A ecf from (i)
sends impulse to, Purkyne fibres / Bundle of His / ventricles / septum ;
allows atrial systole to complete before ventricular, systole / contraction(s) ;
A idea that allows ventricles to fill (before they contract)
A idea that allows atria to, empty completely / complete contraction
function of the left atrioventricular (bicuspid) valve.
either
stops backflow (of blood) ;
(stops backflow) from ventricle to atrium ; R if ref. to right
or
allows one-way flow of blood ;
allows flow from atrium to ventricle ; R if ref.
function of the sinoatrial node (SAN)
) acts as a pacemaker / regulates heartbeat ;
A ref. to myogenic / described e.g. as rythmn / AW
releases / AW, waves of excitation / depolarisation / (electrical) impulses / action
potentials ;
R nerve impulses / signals / messages / waves unqualified
atrial systole / atrial contraction(s) ; A initiates, heart beat / cardiac cycle
ref. to nervous innervation allowing changes ;
Describe and explain how the structure of the human gas exchange surface is adapted
for maximum efficiency.
1 many alveoli ;
2 large surface area ; I high SA:V ratio / increase SA
3 many capillaries / network of capillaries ; I good blood supply
4 (so) maintain, diffusion / concentration / partial pressure, gradient(s) ;
5 lining / epithelium / wall, of, alveoli / gas exchange surface, is thin / one cell thick /
squamous ; I thin interstitium
R ‘cell walls of’ R lungs R alveoli are one cell thick R endothelium / membrane
6 (so) short diffusion distance / only diffuse through two cells ;
7 ref. to, elastin / elastic fibres ; I alveoli are elastic
8 (so) allows alveoli to, increase in volume / expand / stretch / stop bursting / recoil ;
R contract
9 (alveolar type II cells secrete) surfactant ;
10 (so) reduces surface tension ;
Explain briefly how sucrose is moved, or translocated, through sieve tubess
dissolved in, water / sap ; A in solution
mass flow ;
down (hydrostatic) pressure gradient / moves from high(er) to low(er) pressure (potential) ;
A symbol – ψp
AVP ; e.g. from source to sink
loading by, companion / transfer cells, requires ATP / is active ;
I ATP required for mass flow
) Suggest how the oxygen that is not combined with haemoglobin is transported in the
blood.
(in solution /dissolved) in the plasma / cytoplasm of red blood cells ;
Explain why a long-term smoker would have a lower volume of oxygen combined with
haemoglobin in the alveoli at 13.3 kPa.
two from
carbon monoxide, combines with haemoglobin / forms carboxyhaemoglobin ;
irreversible /permanent / stable compound /AW ;
reduces haemoglobin available to transport oxygen ;
alveolar walls /elastin, broken down (in emphysema/COPD) ;
less surface area for, absorption of oxygen / gas exchange ;
The investigation was repeated in the presence of carbon dioxide. The volumes of oxygen
combined with haemoglobin at partial pressures of oxygen below 8.0 kPa were less than
shown in Fig. 5.1.
Name this effect and explain the advantage of this decrease at partial pressures of oxygen
below 8.0 kPa.
1 Bohr, effect / shift ;
AND
to max 2 (‘more’ only needs to be used once)
2 carbon dioxide decreases affinity of haemoglobin for oxygen ;
3 more oxyhaemoglobin dissociates (than at a lower concentration of carbon
dioxide) ;
A oxyhaemoglobin dissociates more readily
A haemoglobin, releases /AW, more oxygen
4 more oxygen for (rapidly) respiring, tissues / cells ;
5 to meet the demand for increase in (aerobic) respiration ;
A to provide, enough / sufficient, oxygen for respiration
ora e.g. delays onset of/ prevents, anaerobic respiration
