Organisms exchange Surfaces Unit 3

Question 1

whats the total oxygen requirement correlated to and the rate of absorption of gases by an organism

Answer 1

oxygen- correlated to its total volume. the bigger the organism the more oxygen it requires. - larger/ more cells therefore requiring more energy for cellular processes
the rate of absorption of gases by an organism is correlated to the size of its SA

Question 2

What does the sa:v show

Answer 2

Shows the relationship between the size of the surface area and the size of the volume
Both values must the ‘same’ units
Volume is always at 1 - this allows direct comparison between organisms of different sizes.

Question 3

How do Single-celled organisms/ small organisms exchange gases across their body surface:

Answer 3

Single-cellular organisms exchange materials by diffusion on their surface w their environment
They have a short diffusion pathway as they are small
A large SA:Vol ratio due to their small volume compared to the surface area of their cell surface membrane.

Question 4

Multi-cellular/ larger organisms exchange gases across their body surface.

Answer 4

Larger organisms have lower surface area to volume ratio:
• Diffusion is too slow as some cells are deep within the body
• A large volume of animal has requirements too high for the available surface area

Question 5

What have large/ multicellular organisms done to overcome slow diffusion

Answer 5

To overcome this, organisms have developed adaptations.
1. Changes to body shape such as folded thinner or longer
• Increases SA:V and overcomes long diffusion pathway
2. Development of systems, such as a specialised organ for gaseous exchange
• Increases SA:V and overcomes long diffusion pathway
• Maintain a concentration gradient for diffusion eg. by ventilation / good blood supply

gills in fish
lungs in mammals
Gills are folded into lamella
Lungs are folded into alveoli
The oxygen diffuses into the circulatory system (mass transport) to deliver gases directly to cells.

Question 6

Surface area: volume and heat loss in smaller animals and adaptations

Answer 6

Smaller animals have a larger surface area to volume ratio compared to larger animals. This means that More heat loss per gram/in relation to body size by radiation compared to larger animals.In order to maintain a constant body temperature, smaller animals have a higher metabolic rate per gram of body mass so (Faster rate of) respiration and These chemical reactions release heat which is used to maintain body heat.
Adaptations for heat loss
Organisms that live areas of high temperatures tend to have adaptations to enable them to stay cool.
These adaptations increase their surface area: volume ratio and can include a smaller body size (compared
to similar species in cooler climates), larger ears, longer faces and longer noses.
Organisms that live in areas of cold temperatures are adapted to reduce their surface area: volume ratio,
this decreases the loss of heat via radiation and helps maintain their internal body temperature.
Adaptations can be: a larger body size, smaller ears, and compact facial features.
larger surface area to volume ratio
more heat los per gram of body mass
higher metabolic rate per gram of body mass.
** so faster respiration
**

Question 7

units in order of largerst and how to convert eg m, dm

Answer 7

( M. )
x10 ( dm ) div by 10
x10 ( cm ) div by 10
x10 ( mm) div by 10
x1000 ( ųm ) div by 1000
x1000 ( nm ) div by 1000

Question 8

Use your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse. 3marks

Answer 8

Mouse:
(Smaller so) larger surface area to volume ratio;
More heat loss (per gram/in relation to body size);
(Faster rate of) respiration

Question 9

Describe how gas exchange occurs in Single-celled organisms and large organisms:

Answer 9

Single-celled organisms exchange gases across their body surface by diffusion:
• They have a large surface area to volume ratio and a short diffusion pathway
Large organisms have specialised gas exchange surfaces:
They have a large surface area for diffusion
Thin surface, so short diffusion pathway
Maintenance of a steep diffusion gradient

Question 10

Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake.

Answer 10

1. Larger organisms have a smaller surface area:volume (ratio)
   2.Overcomes long diffusion pathway

Question 11

Describe The tracheal system and gas exchange in an insect

Answer 11

Spiracles lead to tracheae that lead to tracheoles. Open spiracles allow diffusion of oxygen crom air
Oxygen diffuses in, down a concentration gradient, through the open spiracles and into tracheae. The tracheae are lined with rings of chitin to prevent them from collapsing during ventilation.oxygen diffuses directly into the respiring cells so no blood’s required
The tracheoles are not lined with chitin and so are permeable - this makes them the site of gas exchange in insects.

Question 12

Features of gas exchange in insects:

Answer 12

Short diffusion path
• Tracheoles are in direct contact with (and sometimes enter them) the insects body cells.
• Insects are small maintaining an overall short diffusion pathway from spiracles to respiring tissues.
• The walls of the tracheoles are thin.

Concentration gradient:
• The cells respire using the oxygen so the concentration of oxygen at the cells remains low.
• Body can be moved by muscles to move air so maintains concentration gradient for oxygen and carbon dioxide.

Large surface area:
• Tracheoles are very branched.

Question 13

Describe how insects are evolved to prevent water loss

Answer 13

•Cuticle in tracheae impermeable so reduce water loss
•body covered in waxy cuticle
•spiracles close preventing waterloss
spiracles are lined by hairs which trap the water vapour around the spiracle. This reduces the water potential gradient so less water is lost.

Question 14

Describe how an insects able to obtain oxygen and limit water loss (6 marks)

Answer 14

Air enters through spiracles through trachea. Creates diffusion gradient in trachea.
oxygen diffuses into the cells
Body covered with waxy cuticle
spericals able to close reducing water loss

Question 15

what happens to tracheoles during exercise

Answer 15

Fluid in the end of tracheoles moves into tissues during exercise.
• Cells produce lactate by anaerobic respiration.
• Reduces water potential.
• Water moves in down W gradient by osmosis.
• Increases volume in tracheoles and reduces pressure to draw more in.
• Diffusion through air is faster.

Question 16

How have fishes adapted for efficient exchange of gases and why

Answer 16

Water has a lower oxygen content than air, and diffusion rates are slower in water than air. This means that fish have developed a very efficient method of gas exchange to meet their oxygen demand.
Fish exchange gases at the gills.
Short diffusion pathway:
* Gills have a single layer of epithelial cells and the capillaries within the gills have a single layer of endothelial cells.
(Lamallae are thin so short diffusion pathway to blood)
Large surface area:
* The gills are folded into filaments, and these are further folded into lamellae.
Concentration gradient:
* The gills have lots of blood capillaries.
* Blood in the capillaries flows in the opposite direction to the flow of water over the gills - this is called counter current flow.

Question 17

What’s counter current flow in fish and how’s oxygen diffused

Answer 17

Counter current flow: water and blood flow in opposite directions so maintains diffusion along length of lamella
Diffusion of oxygen
There is a diffusion gradient favouring
the diffusion of oxygen from water
into the blood all the way across the
gill lamellae, Almost all the oxygen
from the water diffuses into the blood.

Question 18

How does co2 enter leafs and where does gas exchange occur

Answer 18

Plants need CO2 For photosynthesis and produce O2 as a waste gas.but they need it for respiration as plants respire all the time
Carbon dioxide diffuses into the leaves down a concentration gradient through pores in the surface of the leaf called stomata.
Gas exchange occurs at the surface of the mesophyll cells. The mesophyll ells are where most of the photosynthesis occurs - particularly the palisade mesophyll cells - their tall and long shape increases the surf -ace area for gas exchange.

Question 19

What do plants have to increase efficiency of gas exchange

Answer 19

Large surface area:
• Large, flat leaf
• Tall, long palisade mesophyll cells.
Short diffusion pathway:
• Thin leaf.
• Air spaces.
Concentration gradient:
• Mesophyll cells use the carbon dioxide, maintaining a low concentration at the mesophyll cells.
Stomata:
The stomata can open (to allow gasses through) and close (to reduce water loss)
The two guard cells control the opening/closing of stomata.

Question 20

How do plants reduce water loss

Answer 20

All plants can lose water through their stomata by diffusion/evaporation in a process called transpiration.
To reduce water loss most plants can do the following:
* Stomata can close when the guard cells lose water and become flaccid, further reducing water loss.
* The leaf is covered in a hydrophobic, waxy cuticle which reduces water loss from cells by evaporation.
* Most stomata are on the lower surface of the leaf, as this reduces the loss of water by evaporation out of the stomata.
15

Question 21

Which types of plants can further reduce water loss:

Answer 21

Xerophytes are plants adapted for hot and dry conditions
• curled leaf shape so trap water vapour and decrease in water potential gradient;
•Thick cuticle so increase in diffusion distance
• Sunken stomata, humid air is trapped reducing water potential gradient between inside leaf and humid trapped air
•Hairs on leaves so reduction in air movements and trap water vapour so waterpotential gradient decreased
•Stomata in puts so trap water vapour and water potential gradient decreased
• waxy cuticle reduces evaporation

Question 22

Whys counter current so important in fishes and what is it

Answer 22

When water flows over the gills in the opposite direction to the flow of blood in the capillaries.
It ensures equilibrium is not reached and that diffusion gradient maintained across the entire length of gill lamella

Question 23

Describe how oxygen in air reaches capillaries surrounding alveoli in lungs. No breathing details. 4 marks

Answer 23

Air enters the
trachea and bronchi and bronchioles, down pressure gradient
across alveolar epithelium across endothelium capillary down diffusion gradient
into blood

Question 24

Adaptations of alveoli

Answer 24

There are many alveoli so a large surface area
Shart diffusion distance
thin walls and Alveolar epitheliam and capillary endothelium are just one cell thick. creates short diffusion distance. Cells are flattened
Steep concentration gradient
Many capillaries close to aveoli to maintain good blood supply and maintain steep concentration gradient
Well-ventilated to bring (fresh air) O2 to the surface and take (stale air) CO2 away and maintain steep concentration
gradient for O2 and CO2

Question 25

ventilation in humans

Answer 25

To maintain the diffusion of gases across the alveolar epithelium air must be constantly moved in and out of the lungs The diaphragm and internal/external intercostal muscles contract to change the volume of the thorax, so changing the air pressure. Air always moves from higher to lower air pressure BREATHING IN External intercostal muscles contract so ribcage moves up and out Internal intercostal muscles relax Diaphragm contracts so it flattens (These 2 things) increases the volume of the thorax so pressure decreases. Air pressure in thoracic cavity decreases below atmospheric pressure. Air moves into lungs down pressure gradient. BREATHING OUT External intercostal muscles relax so ribcage moves down and in. Internal intercostal muscles contract Diaphragm relaxes and moves up and returns to domed shape (These) decreases the volume of the thorax so pressure increases.Air pressure in thoracic cavity increases above atmospheric pressure, Pressure in the thorax higher than outside so Air moves out of lungs down pressure gradient

Question 26

Described forced respiration

Answer 26

Internal intercostal muscles contract pulling the ribcage further down and in. External intercostal muscles relax. causes decrease in thoracic cavity air pushed down concentration gradient

Question 27

What happens during digestion

Answer 27

During digestion, large insoluble biological molecules are hydrolysed to smaller soluble molecules. Large food molecules like starch/proteins/lipids are too big to be absorbed from the gut into the blood across the cell membranes. Digestive enzymes are produced by specialised cells in mammals to catalyse the breakdown. Enzymes are specific to substrates so different enzymes are needed

Question 28

Carbohydrate digestion:

Answer 28

Mouth: Salivary glands produce the amylase. Salivary amylase hydrolyses glycosidic bonds in starch to form maltose. starch To maltose by amylase Pancreas: Produces pancreatic amylase. Produces alkali fluid Small Intestine: Disaccharidases attached to the epithelial cells lining the ileum hydrolyse glycosidic bønds in disaccharides to form monosaccharides. Maltose to glucose by maltase Membrane bound Full digestion of starch: Starch is hydrolysed to maltose catalysed by amylase (salivary) amylase is produced by salivary glands which release it into the mouth and (pancreatic) amylase is also produced by the pancreas and released into the small intestine. Membrane-bound disaccaridases are attached to the membranes of epithelial cells in the ileum (small intestine). They break down disaccharides eg. Maltose, into monosaccharides

Question 29

Protein digestion

Answer 29

Occurs in stomach hydrolysed by 3 types of protease enzymes: endopeptidases, exopeptidases and dipeptides into amino acids and ACTIN (enzyme required for complete hydrolysis of proteins to amino acids) Some Endopeptidases are produced by the pancreas and secreted into the small intestine. Other types of endopeptidases are produced by the stomach celks and work in acidic conditions using HCL in the stomach Endopeptidases hydrolyse internal peptide bonds within a protein,&act in the middle of protein.(hydrolysing long polypeptides into shorter polypeptides). This increases the surface area for exopeptidases and speeds up full hydrolysis of proteins Exopeptidases, hydrolyse and act on the bonds at the end of proteins to remove single amino acids More surface area Dipeptidases are located on the cell surface membrane of epithelial cells in the small intestine and act on dipeptides and produces amino acids

Question 30

Lipid digestion

Answer 30

Lipids are hydrolysed to monogycerides, and fatty acids catalyzed by lipase. (by breaking of ester bonds by addition of water) Lipases are made in the pancreas and workIn the small intestine. Bile salts produced by the liver **emulsify large droplets of lipids into small droplets With a larger surface area for lipases to work on so faster hydrolysis) The monoglycerides and fatty acids form micelles with the bile salts micelles are lipid droplets surrounded by bile soluble in Water. they make the fatty acids soluble in water and allow them to be carried to the epithelial cell in the ileum Lipid digestion can be seen by measuring the change in pH. As lipids are hydrolysed the fatty acids make the solution more acidic. The faster the change in pH the faster the hydrolysis of the lipids. Measurement of lipases rate of reaction in this way means that a pH buffer can not be used as the buffer WOuld maintain a constant pH which is not desired in this type of investigation. Use of a pH meter would be the most accurate way to measure the pH change Comparisons between solutions containing bile salts and those without could also take place

Question 31

What happens after digestion

Answer 31

The products of digestion are absorbed across the ileum epithelial cell membranes: After hydrolysis, the smaller saluble products of digestion are absorbed from a part of the small intestie called the ileum.

Question 32

How is The structure of the ileum is highly adapted to ensure rapid absorption:

Answer 32

The lleum is very long and is folded into structures called villl. This increases surface area for absorption. Each villus has a good capillary network, and a network of tubes called a lacteal which is part of the Lymph system. Both rapidly remove absorbed molecules, maintain a steep concentration gradient. The lining of the ileum is made of one layer of epithelial cells and the capillaries are one layer of endothelial cells - this ensures a short pathway for absorption

Question 33

Adaptations of the epithelial cells:

Answer 33

Folded membrane and microvilli so large surface area. Large number of carrier proteins so fast rate of absorption. Large number of mitochondria so make more ATP Membrane bound enzymes so maintains concentration gradient

Question 34

Absorption of monosaccharides and amino acids

Answer 34

When the concentration of amino acids or monosaccharides is high in the ileum, they move into the epithelial cells by facilitated diffusion. At lower concentrations of amino acids and monosaccharides such as glucose they are taken up by co transport. 1) sodium ions actively transported out of cells into blood 2) this creates and decreases sodium concentration gradient inside epithelial cells 3) sodium moves back into the cell from the intestinal lumen via carrier protein by co transport bringing glucose with it 4) glucose is now at high concentration in the cell and so exists by facilitated diffusion into the blood to the capillary

Question 35

Absorption of monoglycerides and fatty acids

Answer 35

relies upon bile salts which emulsify lipids, increase surface area for lipase activity and form micelles Micelles contain bile salts and fatty acids. Micelles make the fatty acids soluble in water solution in the lumen of the ileum and transport the fatty acids and monoglycerides to the cell membrane of the epithelial cells. Once at the cell membrane of the epithelial cells the micelle releases the fatty acids and monoglycerides. As the fatty acids and monoglycerides are small and hydrophobic they cross the cell membrane (into the epithelial cell) by diffusion through the phospholipid bilayer. fatty acids absorbed by diffusion Once inside the cell, the triglycerides are reformed in the smooth endoplasmic reticulum vescicles move to cell membrane .The triglyceride is transported to the Golgi apparatus where the triglyceride is added to a protein modifying it into a structure called a chylomicron. This chylomicron is packaged into a vesicle and exported out of the cell. The chylomicrons move into lacteals where they are transported around the body Bile salts produce micelles with monoglycerides and fatty acids, transports them to the epithelial membrane to be absorbed by diffusion. Triglycerides are reformed in the RER. The Golgi produces chylomicrons from triglycerides and proteins. The chylomicrons are exported by exocytosis Chylomicrons are absorbed into the lacteals in the villi

Question 36

Describe the role of micelles in the absorption of fats into the cells lining the ileum

Answer 36

Micelles include bile salts and fatty acids. Make fatty acids soluble in water Carry fatty acids to cell of the ileum Maintain a high concentration of fatty acids to cell. Bile salts released Fatty acids absorbed by diffusion

Question 37

Haemoglobin describe it

Answer 37

A quaternary protein that carries oxygen around the body The haemoglobins are a group of chemically similar molecules found in many different organisms. * Found in the red blood cells * Protein with a quaternary structure (more than 1 polypeptide chain) * Each of the four chains has a haem group (Fe) that can bind to an oxygen molecule making oxyhaemoglobin * The cooperative nature of oxygen binding: First molecule of oxygen to bind causes a change in the shape of haemoglobin, this uncovers other binding sites making the binding of further oxygens easier.

Question 38

describe how Haemoglobin loads (pick up) O2 in the lungs and unloads (release it) in respiring tissue,and the oxyhaemoglobin curve

Answer 38

* Haemaglobin has a higher affinity for oxygen At high O2 partial pressures eg. in the lungs O2 is loaded * Haemoglobin has low affinity for oxygen At low O2 partial pressures eg. in respiring tissues . More O2 is unloaded. More O2 released at the same partial pressure and bigher rate of respiration means high demand of oxygen– due to the high concentration of carbon dioxide in these tissues,

Question 39

describe haemaglobin shift to the left

Answer 39

The shape of the haemoglobin molecule varies between different animals. This causes the haemoglobins to have different affinities for oxygen. The different shapes are due to different genes coding for different amino acid sequences. This results in different primary sequences and therefore different tertiary shapes. e.g. Foetal haemoglobin and animals living in low oxygen environments have a higher affinity of oxygen. Key points for curves to the left * Haemoglobin has a higher affinity for oxygen * Haemoglobin loads oxygen more readily at lower oxygen partial pressures and can be saturated at lower O2 partial pressures * Oxygen can be supplied to respiring tissues * It unloads oxygen only at very low partial pressures

Question 40

Effect of Carbon Dioxide and The Bohr Shift to the right

Answer 40

Respiring tissues produces carbon dioxide which dissolves and forms Carbonic acid and H+ this reduces the pH. This causes a change in the haemoglobin’s shape and thus reduces the affinity of the haemoglobin for oxygen. * The haemoglobin has a lower affinity for oxygen * more oxygen unloaded and released at same partial pressure to the respiring tissues allowing faster respiration to provide energy for metabolic reactions * high rate of respiration means high demand of oxygen

Question 41

whats affinity, partial pressure and bohr affect

Answer 41

Affinity – How readily oxygen associates to haemoglobin Partial pressure – The pressure created by a gas in a specific space Bohr effect – the effect of carbon dioxide on the affinity of haemoglobin; the more carbon dioxide the lower the affinity of haemoglobin for oxygen

Question 42

Describe how CO2 in the air outside a leaf reaches the mesophyll cells inside the leaf (4 marks)

Answer 42

via stomata stomata opened by guard cells diffuses through air spaces down conc gradient

Question 43

describe adv and disadv of having a higher stomatal density

Answer 43

adv- More CO2 uptake, more photosynthesis so faster growth disadv- more water loss, less photosynthesis so slower growth

Question 44

describe a method you could use to find the surface area of a leaf

Answer 44

Draw around leaf on graph paper count squares multiply by 2

Question 45

Insects abdominal pumping and ventilation

Answer 45

A compressed abdomen increases pressure. Air containing higher levels of CO2 is forced through the abdominal spiracles out of the trachea, An expanded abdomen lowers the pressure, air containing higher levels of O2 is forced through the thoracic spirackes into the trachea Ventilatin- to force air in, expand abdomen, increase in volume, decrease In pressure, air moves in, forces air out, Compressed abdomen, volume decreases pressure increases air forced out

Question 46

How do substances move over short distances

Answer 46

by osmosis, diffusion and active transport

Question 47

How do substances move over long distances

Answer 47

by mass flow

Question 48

Whats mass flow

Answer 48

In mass flow a fluid moves in a particular direction due to a force In living organisms this is the movement of water, dissolved solutes and suspended objects Mass flow requires a source of energy to pump the fluid but is much faster than diffusion Examples include: circulatory systems in animals, xylem and phloem in plants

Question 49

Why do large multicellular organisms need to use mass flow

Answer 49

Surface area:volume ratio too small Distance for diffusion too long Mass flow takes gases and nutrients close to all cells

Question 50

What type of circulatory system do mammals have

Answer 50

closed

Question 51

What's the closed circulatory system

Answer 51

Blood is enclosed within blood vessels and pumped around by the heart.

Question 52

Whats the double circulatory system

Answer 52

blood passes through the heart twice in one. There is one circuit that delivers blood to the lungs and another circuit that delivers blood to the rest of the body.Enables separate circulation to lungs so can maintain higher pressure to rest of body organs

Question 53

What do the arteries do?

Answer 53

take blood away from the heart to the rest of the body – blood is under high pressure

Question 54

what do veins do

Answer 54

return blood back to the heart – blood is under low pressure

Question 55

What do the capillaries do

Answer 55

connect arteries and veins, site of exchange

Question 56

order of the heart things, ventricle.. artery

Answer 56

Ventricle (of the heart) → Artery → Arteriole → Capillary → Venule → Vein → Atrium (of the heart)

Question 57

Explain why mammals have a closed double circulatory system

Answer 57

To manage the pressure of blood flow. The blood flows through the lungs at a lower pressure. This prevents damage to the capillaries in the alveoli and also reduces the speed at which the blood flows, enabling more time for gas exchange. The oxygenated blood from the lungs then goes back through the heart to be pumped out at a higher pressure to the rest of the body. This is important to ensure that the blood reaches all the respiring cells in the body.

Question 58

Name the major blood vessel attached to the heart, lungs and kidneys

Answer 58

• Heart (vena cava, aorta, pulmonary artery and pulmonary vein • Lungs (pulmonary artery and pulmonary vein) • Kidneys (Renal artery and renal vein)

Question 59

Tissue fluid is the liquid that surrounds cells. What does it contain?

Answer 59

water,glucose, amino acids, fatty acids, ions, oxygen

Question 60

Describe the Artery's wall, endothelium, limen, elastic content, valves, pressure and valves

Answer 60

Wall - Thick muscular to withstand pressure Endothelium - smooth to reduce friction and Present but folded to allow for stretch and smooth. Lumen - Narrow maintains pressure. Elastic content - elastic tissue to allow recoil and stretches when ventricles contract(High can stretch and recoil with changing pressure) Valves - No (apart from aorta and pulmonary artery) Pressure - High Pressure drops when ventricles relax, but stays quite high due to elastic recoil of walls. Pressure decreases with distance from heart as there is resistance to blood flow due to friction with the larger surface area of walls and dissipation of energy in elastic recoil. Walls - Thick wall to resist pressure. Thick layer of elastic tissue stretches with high pressure pulse then recoils maintaining pressure pushing the blood further. Smooths out flow.. Thick muscle prevents rupture

Question 61

Describe the Veins wall, endothelium, limen, elastic content, valves, pressure and valves

Answer 61

wall- Thiner endothelium- Present and not folded(dont have to stretch) lumen- Wide, reduce resistance, allow large volume. Wide lumen to fit large volume of blood, and lower resistance elastic content - Low valves - yes prevent backflow Pressure- low. Pressure always low. Large volume means low flow rate Walls- Thin walls as pressure is low. Walls are squeezed by skeletal muscle and breathing movements to push blood.

Question 62

Describe and explain four ways in which the structure of a capillary adapts it for the exchange of substances between blood and the surrounding tissue.

Answer 62

1. permeable capillary wall 2. narrow lumen, reduces flow rate giving more time for diffusion; 3. thin walls, reduces diffusion distance; 4. flattened (endothelial) cells, reduces diffusion distance; Capillary pores: allow some substances eg. Water, white blood cells (not red blood cells) to leak out through the wall. This further reduces pressure Takes blood as close as possible to cells for rapid transfer of oxygen, carbon dioxide and glucose between blood and respiring cells. Friction of blood with the walls and large total cross sectional area lowers the pressure and slows blood flow which enhances exchange

Question 63

Describe Arterioles

Answer 63

Arteries branch into arterioles they have muscular walls which can contract if contract they constrict the aterioles reducing blood flow: if relax they dilate the arterioles this way the arterioles are able to regulate the flow of blood to the capillary beds

Question 64

Explain how water from tissue fluid is returned to the circulatory system.

Answer 64

. (Plasma) proteins remain; 2. (Creates) water potential gradient 3. Water moves (to blood) by osmosis; 4. Returns (to blood) by lymphatic system;

Question 65

Describe tissue formation and return of tissue fluid

Answer 65

1. hydrostatic pressure of blood high at arterial end due to contraction of the left ventricle. (water potential relatively high) 2. water and small soluble molecules forced out of capillary e.g amino acids, salt ions and glucose 3. This reduces the volume of the blood so means the remaining blood has a greater volume of capillary to contain it and therefore the pressure in the capillary (tissue formation) 4. plasma proteins and large molecules e.g. blood cells remain; 5. This reduces the water potential of the blood 6. water moves back into venules end of capillary by osmosis; 7. lymph system collects any excess tissue fluid which returns to the blood

Question 66

How can high blood pressure result in oedema

Answer 66

high blood pressure= high hydrostatic pressure • Increase in hydrostatic pressure at the arteriole end • More water is forced out of the capillary into the tissue fluid • Water potential gradient remains the same so water moving back into the capillary does not increase so more tissue fluid formed

Question 67

How does (plasma) Protein Deficiency (diet/not produced by liver/over excretion by kidneys) cause oedema

Answer 67

Less plasma protein in blood water potential of blood isn't lowered as much/ waterpotential of plasma increases water potential gradient is not as high Less water moves back into capillary by osmosis at venule end

Question 68

How do blocked lymph vessels cause oedema

Answer 68

* Excess tissue fluid is unable to be absorbed by the lymph vessels * Excess water accumulates in the tissue fluid

Question 69

Describe how the hearts a specialised organ to pump

Answer 69

The heart is made up of cardiac muscle and has it own blood supply from a blood vessel - the coronary artery. It is split into the left and right sides (blood from each side does not mix) and 4 chambers. Atria receive blood from veins and ventricles pump blood into arteries. Ventricles are made of thicker muscle than the atria because blood is to be pumped further away and so a high pressure needs to be generated by more muscle. Atria only pump blood to ventricles. The left side of heart is thicker as blood is to be pumped to all the body systems so a higher pressure is needed. The right side of the heart pumps blood to the lungs only, so less resistance. Additionally a higher pressure to the lungs would force more fluid out at the capillaries (see formation of tissue fluid) which would impair gas exchange.

Question 70

Describe the function of the components of the external structure of the heart

Answer 70

Aorta - Carries oxygenated blood from L ventricle to general body Vena Cava- Carries deoxygenated blood back to R atrium from the body Pulmonary Artery- Carries deoxygenated blood from R ventricle to lungs Pulmonary vein- Carries oxygenated blood back to L atrium from lungs Coronary arteries- Supply the heart muscle tissue with oxygenated blood

Question 71

Describe the function of the components of the internal structure of the heart

Answer 71

Atrium (atria) Contracts to force blood into the ventricle ventricle - Contracts to force blood into aorta / p artery bicuspid valve- Prevents backflow of blood from L ventricle to L atrium tricuspid valve- Prevents backflow of blood from R ventricle to R atrium semi lunar valves- Prevents backflow of blood from arteries to ventricles cords (valve tendons) - Prevent valves from inverting

Question 72

What does the cardiac cycle do

Answer 72

maintains the unidirectional flow of blood in the heart. Unidirectional flow of blood ensures maximum efficiency in the delivery of oxygen and nutrients to cells and the removal of waste products, ensuring that oxygenated and deoxygenated blood do not mix. Systole - contracts Diastole - relaxes

Question 73

Describe the cardiac cycle

Answer 73

Ventricular Diastole (whole heart diastole): • Heart relaxes (both atria and ventricles.) Pressure drops. • Blood fills atria from veins (vena cava/pulmonary vein), this is often referred to as passive (re)filling. Atrial systole:(Atria both contrachne) • Cardiac muscle in the atria contract. • Pressure in atria increases • higher pressure in atria than ventricles opening the atrio-ventricular valve • Blood forced into ventricles • Valves in veins stop blood going back into veins (vera cava, pulmonavy eir heme vame) Ventricular Systole: Ventricles contract from the base upwards, causes increase in blood pressure • Ventricular pressure higher than atrial pressure shutting the AV valve,preventing backflow into atria. • Ventricular pressure higher than aortic pressure, opening the semi-lunar valve • Blood forced through semilunar valves into arteries (aorta/pulmonary artery) After Ventricular Systole the heart fully relaxes again (diastole), there is lower pressure in the ventricles than in the arteries, the semi-lunar valves close, preventing back flow of blood into the ventricles. The elastic recoil of the arteries means the arteries initially expand to accommodate the high volume of blood forced out of the ventricles but then recoils, decreasing the diameter of the vessel again, maintaining the high blood pressure and ensuring the continual forward flow of the blood, away from the heart.

Question 74

What is transpiration?

Answer 74

Loss of water vapour from the stomata by evaporation

Question 75

4 Key conditions that affect the rate of transpiration

Answer 75

light intensity - Positive correlation. more light causes more stomata to open = larger surface area for evaporation temperature - positive correlation. more heat means more kinetic energy, faster moving molecules and therefore more evaporation humidity - negative correlation.more water vapour in the air will make the water potential more positive outside the leaf, therefore reduces the water potential gradient. wind - positive correlation. more wind will blow away humid air containing water vapour, therefore maintaining the water potential gradient

Question 76

Describe the xylem

Answer 76

Xylem is the tissue that transports water and ions in stems and leaves: * Consists of dead cells * Cells walls contain lignin which water can adhere to and which provide strength to the xylem to prevent inward collapse * No cytoplasm or organelles (tubes are hollow) for no impeded flow Tubes with no end walls that form a continuous system of tubes for water Transport * This allows water to move as a continuous column with no impeded flow * Pits (small gaps in the xylem cell wall): * Allow horizontal movement of water

Question 77

How does briefly water pass through the root and what does this rely on?

Answer 77

1. Adhesion - Forces between the water molecules and hydrophilic lining of the xylem walls 2. Cohesion - Force between Water molecules Forming an Unbroken column In the Xylem 3. Tension - Pull generated by water evaporation. This creates a negative pressure inside the xylem (pressure is lower inside the xylem than outside of it) 4. Transpiration - evaporation of water, as water vapour, from the leaves and shoots of plants. Usually through the stomata

Question 78

Describe how water moves up the xylem

Answer 78

1. Transpiration - diffusion of water vapour through stomata. This lowers water potential of the leaf cells and water moves from the higher water potential in the xylem to the leaf cells by osmosis. 2. Water is pulled up the xylem which creates tension. 3. Water molecules cohere together by hydrogen bonds formung a continuous water coloumn. 4. water molecules also stick to the xylem cell walls by adhesion. 5. water enters the roots from the soil by osmosis. it travels across the root cortex into the system. An increase in transpiration causes higher tension in the xylem reducing pressure, reducing the diameter. (due to the increase upwards pull on the continuous column of water). The higher the rate of transpiration, the higher the tension, and the lower the diameter of the xylem.

Question 79

whats a potometer and what does it assume?

Answer 79

A potometer creates a sealed environment with water that can be used to measure water uptake based on the distance an air bubble moves over time * Assumes water loss by transpiration is approximately the same as water uptake by roots * Some water may be used in photosynthesis and some taken in to maintain cell turgor. Measurements may also be affected by water made in respiration.

Question 80

how to set up potometer

Answer 80

* Set up the equipment under water and cut the shoot under water so that air bubbles do not enter xylem and break the continuous water column * Seal the joins with Vaseline – prevents leaks and/or air being drawn in * Dry off the leaves after removing from water, this would decrease the water potential gradient and effect the rate of transpiration. * Use large number of leaves for measurable rate. * Draw an air bubble in * Leave to equilibrate then measure the distance the air bubble moves in a given time. * Move bubble back to the start using a reservoir of water and repeat to increase reliability or set up new condition eg. Different light intensity

Question 81

How do tendencies help to maintain flow of blood in one direction through the heart?

Answer 81

Due to high pressure in the ventricle, it prevents valve from being inverted and blood flowing into the atrium

Question 82

Whats translocation

Answer 82

Plants transport the organic products of photosynthesis. These are transported as soluble sucrose in living tubes called phloem. Solutes are loaded in the leaves (the ‘source’)and taken to other parts where they are used for energy requiring processes such as growth eg ATP for active transport) or storage ‘sink

Question 83

What are phloem made up of

Answer 83

living cells, this allows them to produce ATP for sucrose transport. Phloem consist of two cell types: Sieve tube elements: living cells with no nucleus and just a few organelles so less resistance to flow. Their end cell walls have perforations in them called sieve plates Companion cells: Very active cells next to the sieve tubes’ Connected to sieve tubes by plasmodesmata (small holes and connections in cell wall). Lots of mitochondria– provide the energy (ATP) to the sieve tubes for the active movement of sucrose

Question 84

Mass Flow Hypothesis

Answer 84

1. Source produces glucose (by photosynthesis) which is then converted to sucrose. 2. Sucrose solution is actively transported into the phloem by companion cells 3. Lowers Water potential of sieve tube Water moves in from xylem by osmosis – (increased the volume in the phloem causes increased pressure 4. Hydrostatic pressure builds up, forcing the sucrose solution along the phloem by mass flow to respiring cells or storage organ (from a high to a low pressure). 5. At the sink sucrose moves from the phloem into the sink cell by active transport. This lowers the sinks water potential so water moves down a gradient into the sink. 6. Water re-enters the xylem by osmosis. Sucrose is used in root for respiration for storage

Question 85

Evaluating evidence for and against the mass flow hypothesis

Answer 85

For the mass flow hypothesis to be 100% correct the following conditions must be true: 1. Downward unidirectional flow 2. Higher to lower pressure (the phloem has a high hydrostatic pressure) 3. Sucrose moves from source to sink 4. Process is active

Question 86

what have insects done to overcome small sa:v

Answer 86

Insects developed tracheal systems. Which are series of specialised tubes in direct contact with cells. They also maintain a small size to maintain a short diffusion distance.

Question 87

Explain the importance of ventilation

Answer 87

Brings in air containing higher concentration of oxygen & removes air with lower concentration of oxygen. Maintaining concentration gradient

Question 88

explain why an athlete had the same cardiac output but a lower resting heart rate than before 2 MARKS

Answer 88

volume of blood pumped out of left ventricle increased so more blood pumped out so increased strength of heart muscle. (like any muscle in body, if you work muscle it gets bigger and stronger)

Question 89

Whats the equation for cardiac output

Answer 89

co = hr x SV Cardiac output refers to the volume of blood pumped by the heart per unit of time, heart rate (beats per minute) represents the number of times the heart beats per minute, indicating the frequency of cardiac cycles. stroke volume (volume of blood pumped per beat).

Question 90

Adaptations in Cardiac Output

Answer 90

Cardiac output rises during exercise to supply oxygenated blood to muscles, allowing cells to respire and produce ATP. while it decreases during sleep when metabolic demands are lower.

Question 91

Explain how the pressure in a ventricle is related to the thickness of the ventricle wall

Answer 91

thickness of the wall increases because ventricle wall contracts contraction causes increase in pressure

Question 92

Explain why the hydrostatic pressure falls from the arteriole end of the capillary to the venule end of the capillary

Answer 92

Loss of water

Question 93

explain why the water potential of the blood plasma is more negative at the venule end of the capillary than the arteriole end of the capillary

Answer 93

Water forced out of the capillary plasma proteins remain as they are too large to leave Increasing water potential of the plasma proteins

Question 94

give the pathway of red blood cell from kindney to lungs

Answer 94

Renal vein, vena cava to right atrium, rifht ventricle to pulmonary artery