organism exchange

Question 1

surface area to volume ratio

Answer 1

larger the organism= smaller SA:V

Question 2

Fick’s law is…

Answer 2

rate of diffusion= (SA x difference in conc.)/ length of diffusion path

Question 3

single celled organisms…

Answer 3

exchange gases across body due to large SA:V

Question 4

the tracheal system of insects has…

Answer 4

trachea
tracheoles
spiracles

Question 5

adaptation of insect tracheal system…

Answer 5

gases enter + exit through spiracles
gas exchange through diffusion, CO2 conc. gradient from tracheoles to atmosphere
mass transport- contraction of abdominal muscles moves gases along
in flight, muscle cells respire anaerobically to produce lactate, lowering WP so water moves from tracheoles to cells
more air drawn down in to decreases volume in tracheoles

Question 6

structure of mass exchange in fish

Answer 6

gill filaments (at right angles to each other to increase SA)
lamellae in gill filaments (deep folds= increases SA)

Question 7

adaptation of gas exchange in fish are…

Answer 7

lamellae are folded for large SA
lamellae + filaments= thin, increased diffusion rate
use counter current exchange to absorb O2

Question 8

counter-current principal is…

Answer 8

water and blood flow in opposite direction
ensures a favourable conc/ gradient of O2 is maintained across WHOLE LENGTH of lamellae

Question 9

dicotyledonous plants…

Answer 9

exchange gas though stomata
guard cells control opening/closing, helps prevent water loss by evaporation
small SA:V
waxy cuticle (waterproof)
hairy leaves trap water vapour (reduce WP gradient)
cuticle rolls to cover stomata

Question 10

structure of gas exchange in humans

Answer 10

trachea
bronchus
bronchiole
alveolus
diaphragm
lungs
ribs

Question 11

inspiration

Answer 11

external intercostal muscle contracts, internal intercostal muscle releases
ribs pulled upwards and outwards whilst diaphragm contracts and flattens
increased thoracic volume, decreasing air pressure so air forced into lungs

Question 12

expiration

Answer 12

external intercostal muscle relaxes, internal intercostal muscle contracts
ribs pulled downwards and inwards, diaphragm relaxes and is pushed back into dome shape
decreases thoracic volume, increasing air pressure so CO2 is forced into atmosphere

Question 13

alveoli has…

Answer 13

very large SA= higher rate of diffusion
network of capillaries so short diffusion distance
alveolar epithelium is thin

Question 14

amylase is…

Answer 14

produced in salivary glands/pancreas (secrets into the small intestine)
hydrolyses starch into maltose

Question 15

membrane bound disaccharides…

Answer 15

present in membrane small intestine
hydrolyse disaccharides (maltose to monosaccharide like glucose)

Question 16

lipase…

Answer 16

hydrolysis lipids to monoglycerides and fatty acids
present in small intestine

Question 17

adaptations that help lipase

Answer 17

bile salts made by liver emulsify lipids giving large SA so easily hydrolysed by lipase
products can remain associated with bile to form micelles
micelles travel to ileum, broken down when in contact with epithelium, products can diffuse straight into epithelium

Question 18

protease…

Answer 18

hydrolyses proteins (polypeptides) into amino acids
3 types: endopeptidases (hydrolyse peptide bonds in the middle region of the polypeptide chain), exopeptidase (hydrolyse peptide bonds on terminal amino acids), membrane-bound dipeptidases (hydrolyse dipeptides into 2 amino acids)

Question 19

adaptation of amino acids and monosaccharides

Answer 19

co-transport:
1. Na+ and amino acid co-transported from lumen to epithelium
2. K+ actively transported from blood into epithelium
3. amino acid transported into blood via facilitated diffusion

Question 20

haemoglobin is…

Answer 20

globular protein (4 polypeptide chains, quaternary structure)
each haem group has Fe+ ion
has 4 oxygen binding sites
function- carry O2 through blood to respiring tissues

Question 21

loading/unloading; oxyhaemoglobin dissociation curve features…

Answer 21

partial pressure= O2 conc.
at lowest part of graph= low affinity, low chance of oxygen loading onto haem
at highest point of graph= high affinity, saturation increases, high chance of O2 loading onto haem
s shaped because= upon binding of first O2 molecule, tertiary structure of haem changes, making 2nd + 3rd binding easier, so saturation increases (conformational change)

Question 22

Bohr effect is…

Answer 22

CO2 dissolves in blood, forming carbonic acid, lowering blood pH
changes tertiary structure of haemoglobin, so lower affinity
more O2 dissociates at respiring tissues
low affinity= curve shifts to the right
high affinity= curve shifts to left

Question 23

some species have different haem…

Answer 23

mountain =-dwellers have haem with high affinity so is loaded with O2 at Lowe partial pressure
less O2 available at high altitude so good
foetuses, worms have some myoglobin which has high affinity

Question 24

circulatory system of mammals

Answer 24

veins= towards heart
arteries away from heart

Question 25

types of veins and arteries...

Answer 25

vein to hear= vena cava heart to lungs= pulmonary artery lungs to heart= pulmonary vein heart ti body= aorta vein towards liver= hepatic vein towards kidneys= renal

Question 26

structure of the human heart...

Answer 26

enter right atrium via vena cava tricuspid valve to right ventricle pulmonary artery to lungs left atrium bicuspid valve to left ventricle aorta to body

Question 27

adaptation of the human heart...

Answer 27

walls on left are thicker, blood has to be pumped around the whole body, so high muscle power required atria thin- only pump to ventricles ventricles thick- pump to lungs and body

Question 28

cardiac cycle...

Answer 28

cardiac diastole= atria + ventricles relaxed, blood enters atria pressure rises, so AV valves open, blood flows into ventricles down pressure gradient article systole + ventricle diastole= atria contract to ensure blood enters ventricles (ventricular diastole) ventricular pressure slightly incr. shutting AV valves to prevent back flow ventricular systole= ventricles contract, further incr. ventricular pressure so more than that of pulmonary artery/aorta semi-lunar valves open so blood flows into pulmonary artery (right-deoxygenated/aorta, left-oxygenated)

Question 29

double circulatory system...

Answer 29

allows high pressure to be maintained single system wouldn't work- large SA of lung capillaries would decrease pressure so less oxygenated blood delivered to tissues

Question 30

adaptations of arteries

Answer 30

thick muscular layer, so constriction and dilation can control blood volume thick elastic layer to maintain blood pressure and allow stretch and recoil thick wall, prevent bursting due to high pressure

Question 31

adaptations of arterioles

Answer 31

thick muscle layer to restrict blood flow into capillaries thinner elastic layer and walls

Question 32

adaptations of veins

Answer 32

thin muscle and elastic layer and wall due to lower pressure can be flattened easily, helping blood flow to heart, larger SA valves to prevent back flow

Question 33

adaptations of capillaries

Answer 33

no muscle/elastic layer one cell thick form capillary beds, narrow diameter, short diffusion distance

Question 34

formation and return of fluid steps

Answer 34

1. blood enters from arterioles, resulting in high hydrostatic pressure at arteriole end (start) 2. molecules like glucose, amino acids, fatty acids, ions, H2O and O2 forced out (this forms tissue fluid) 3. large molecules like protein ramen in capillaries, lowering water potential 4. at venue end, low hydrostatic pressure and water potential, so H2O re-enters by osmosis (not all) 5. remaining tissue fluid absorbed into lymphatic system, later re-absorbed into capillaries

Question 35

leaf anatomy

Answer 35

xylem= responsible for movement of water] H2O absorbed by root hair cells via osmosis H2O reaches xylem, transported against gravity along long, thick-walled tubes phloem= transports organic substances by translocation (mass flow hypothesis) sieve tube elements, companion cells

Question 36

cohesion tension theory

Answer 36

water is dipolar, so H bonds formed between H2O molecules (cohesion) results in continuous eater column being created in xylem H2O transpires, so column is pulled up the xylem (transpiration pull) puts tension on xylem, making diameter decrease

Question 37

how can xylem form column?

Answer 37

cells= hollow because they are dead, no end walls

Question 38

mass flow hypothesis steps...

Answer 38

1. organic molecules created by photosynthesis transported to companion cells via facilitated diffusion (source) 2. sucrose actively transported into phloem/sieve tube elements by co-transport with H ion 3. this decreases WP so H2O enters phloem form xylem via osmosis 4. this incr. volume= incr. hydrostatic pressure 5. sugars used in respiring cells, incr. WP so they exit by osmosis, decreasing hydrostatic pressure (sink) 6. hydrostatic pressure gradient therefore created from phloem to respiring cells

Question 39

ringing experiment...

Answer 39

1. ring of bark along phloem removed from trunk 3. trunk swells above removed ring, liquid was found to contain sugar 3. showed phloem transported sugars as can't be transported due to removal of phloem ring

Question 40

tracing experiment...

Answer 40

1. plants provided with radioactive- labelled CO2 2. absorbed during photosynthesis to produce sugars, also radioactively- labelled 3. samples then cut and placed on X-ray film, detects radioactive material 3. section containing radioactive sugars was detected, highlighting where phloem was located