Chapter 7 - Mass Transport

Question 1

What does the affinity of haemoglobin for oxygen mean

Answer 1

• the ability of haemoglobin to attract, or bind, oxygen

Question 2

What does the saturation of haemoglobin with oxygen mean

Answer 2

When haemoglobin is holding the maximum amount of oxygen it can bind

Question 3

What does the loading/ association of haemoglobin mean

Answer 3

The binding of oxygen to haemoglobin

Question 4

What does the unloading/ dissociation of haemoglobin

Answer 4

When oxygen detaches or unbinds from haemoglobin

Question 5

What does the oxyhemoglobin dissociation curve show

Answer 5

That oxygen is loaded in regions of high partial pressure of oxygen and unloaded in regions if low partial pressure

Question 6

Explain the positive cooperation of oxygen

Answer 6

at low partial pressure it is difficult for the first O2 molecule to bind to the haemoglobin so requires a large increase in partial pressure (hence why the graph is steep at first)
Once the first O2 molecule binds the quaternary structure of the haemoglobin, it changes in shape, which increases the affinity for the next oxygen to bind so binding the rest of the oxygen molecules only require a small increase in partial pressure (hence why the graph begins to level off)

Question 7

What is the Bohr effect

Answer 7

When carbon dioxide concentration causes the oxyhaemoglobin curve to shift to the right. So the affinity for oxygen decreases because the carbon dioxide dissolves in the blood to form carbonic acid causing pH to decrease and these acidic conditions changes the shape of the haemoglobin slightly decreasing affinity and therefore unloads more oxygen

Question 8

What effect will low CO2 conc have in the oxyhemoglobin affinity curve

Answer 8

Makes it shift to the left as the pH will increase as less H+ ions are released into the blood so the Shape of haemoglobin will change and oxygen affinity increases and therefore more oxygen is loaded

Question 9

Explain the difference between fetal haemoglobin and adult haemoglobin

Answer 9

The fetal haemoglobin has a higher oxygen affinity than the adult haemoglobin as the foetus cannot inhale or exhale, so it’s source of oxygen comes from the mother haemoglobin in the blood supply, so the fetal haemoglobin has to have a high o2 affinity in order to take oxygen from the mother’s haemoglobin

Question 10

Explain the difference between llama haemoglobin and human haemoglobin

Answer 10

Llamas live at high altitudes where there is a low partial pressure of oxygen compared to humans so has a higher oxygen affinity

Question 11

Explain the difference between dove haemoglobin and human haemoglobin

Answer 11

Dove has a lower oxygen affinity compared to humans as they have a faster metabolism for aerobic respiration to provide for contracting muscle (so will produce more co2 causing their oxygen affinity to decrease)

Question 12

Explain the difference between earthworms haemoglobin and human haemoglobin

Answer 12

• earthworms haemoglobin has a higher oxygen affinity than humans as they live underground where there is a low partial pressure of oxygen

Question 13

Why do mammals have a double circulatory system

Answer 13

To mamaage the pressure if the blood flow

Question 14

What does it mean by double circulatory system

Answer 14

That the blood passes through the heart twice in each circuit, with one circuit which delivers blood to the lungs and the other which delivers blood to the rest of the body

Question 15

How does the closed double circulatory system work in mammals

Answer 15

1) the blood flows through the lungs at a lower pressure, this prevents damage to the capillaries in the alveoli and at low speed to enable more time for gas exchange
2) the oxygenated blood from the lungs then goes back through the heart to be pumped out at 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 16

What are the key blood vessels

Answer 16

• coronary arteries
• pulmonary artery and vein (connected to lungs)
• renal artery and vein (connected to kidneys)
• vena cava, aorta, pulmonary artery and vein (connected to heart)

Question 17

Role of coronary arteries

Answer 17

Supply heart with oxygenated blood

Question 18

Properties of the cardiac muscle (thick muscular layer in heart)

Answer 18

• myogenic, meaning can contract and relax without needing any stimulation from the nervous system or hormones
• never fatigues as long as it has a supply for oxygen

Question 19

What happened if coronary arteries become blocked

Answer 19

• can cause coronary heart disease as the coronary arteries won’t receive oxygen and therefore won’t be able to respire so the cells in cardiac muscles will die, resulting in myocardial infarction (a heart attack)

Question 20

Properties of the left and right atria (atrium)

Answer 20

• elastic walls to stretch when blood enters
• thinner muscular wall than ventricular as they do not need to contact as blood is only pumping to ventricles and not to the whole body

Question 21

Properties of the left and right ventricles

Answer 21

• thicker muscular walls to enable a bigger contraction, this creates a high blood pressure to enable blood to flow longer distances

Question 22

Why does the right ventricle have a thinner muscular wall compared to the left ventrical

Answer 22

• As it Pumps blood to the lungs, so blood has to be at a low pressure to prevent damage to capillaries in the lungs and blood flows slowly allowing more time for gas exchange, this means that is has a thinner muscular wall compared to the left ventricle

Question 23

Why does the left ventrical have thicker muscular walls compared to the right ventrical

Answer 23

The left ventricle have thicker muscular walls to enable bigger contractions to create a lot of pressure to pump oxygenated blood to the other more distant organs of the body.

Question 24

Role of vena cava

Answer 24

Carries deoxygenated blood from the body to the right atrium

Question 25

Role of pulmonary vein

Answer 25

Carries oxygenated blood from the lungs to the left atrium

Question 26

Role of pulmonary artery

Answer 26

Carries deoxygenated blood form the right ventricle to the lungs to become more oxygenated

Question 27

Role of aorta

Answer 27

Carries oxygenated blood from the left ventricle to the rest of the body

Question 28

Names of valves in heart and Where they are found

Answer 28

Semi lunar valve - in aorta and pulmonary artery Atrioventricular valve - found between atrium and ventricles - Bicuspid valve (found on the left side) and Tricuspid valve (found in the right side)

Question 29

Role of septum

Answer 29

Separates the deoxygenated blood from the oxygenated blood to maintain a high concentration of oxygen in the oxygenated blood to maintain a concentration gradient to enable diffusion at respiring cells

Question 30

Roles of valves

Answer 30

- enables blood to flow in one direction by opening when pressure is higher behind the valve and closing when the pressure is higher in front of the valve

Question 31

3 stages of cardiac cycle

Answer 31

1) Atrial Systole 2) Ventricular systole 3) Diastole

Question 32

What does systole mean

Answer 32

Contracting

Question 33

What does diastole mean

Answer 33

Relaxing

Question 34

What happens during diastole in the cardiac cycle

Answer 34

1) the atria and ventricular muscles are relaxed 2) semi lunar valves relax 3) blood enters the atria via the vena cava and pulmonary vein increases the pressure within the atria

Question 35

What happens during atria systole of the cardiac cycle

Answer 35

1) the atria muscular walls contract, increasing atrial pressure further 2) this causes the atrioventricular valves to open and blood to flow into the ventricles 3) the ventricular muscle walls are then relaxed (ventricular diastole)

Question 36

What happens during ventricular systole in the cardiac cycle

Answer 36

1) the ventricular muscular walls contract, increasing the ventricular pressure 2) this causes the atrioventricular valves to close and the semi lunar valves to open 3) the blood is pushed out of the ventricles into the arteries

Question 37

What is the cardiac output and stoke volume

Answer 37

Cardiac output = the volume of the blood which leaves one ventricle in one minute Stroke volume = volume of blood that leaves the heart each beat

Question 38

How to work out cardiac output

Answer 38

Stroke volume x heart rate

Question 39

How do atrioventricular valves work

Answer 39

- Open when pressure is higher in atria compared to ventricles - Close when pressure is higher in ventricles than in the atria

Question 40

How do semi lunar valves work

Answer 40

- open when pressure is higher in ventricle than in arteries - closes when pressure is higher in arteries than ventricles

Question 41

Adaptations of arteries

Answer 41

-Collagen - Provides strength to prevent the vessel from bursting and to maintain vessel shape. - Elastic fibres - Contain elastin that lets them stretch and recoil to minimise changes in pressure. - Thick smooth muscle layer - Contracts and relaxes to constrict and dilate the lumen and control blood flow. - narrow lumen to increase pressure

Question 42

Adaptations of of veins

Answer 42

- Collagen - Provides strength to prevent the vessel from bursting and maintain vessel shape. - thinner walls - allow veins to be easily compressed, aiding the flow of blood to heart - Valves - Pocket valves shut to prevent the backflow of blood when veins are squeezed by surrounding skeletal muscle. - wide lumen - This maximises the volume of blood that is carried to the heart.

Question 43

properties of capillaries and how it is an advantage

Answer 43

- narrow lumen, reduces flow rate giving more time for diffusion - single cell thick, reduces diffusion distance - small diameter gives a large surface area to volume ration and reduces diffusion distance - red blood cells in contact with the wall increases time for diffusion - fenestrations to allow large molecules through - flattened cells reduces diffusion distance

Question 44

Properties of arterioles

Answer 44

- thick muscle layer (compared to arteries) to help restrict blood flow into the capillaries - thinner elastic wall than the arteries as the pressure is lower - thinner wall than arteries as pressure is lower - no valves

Question 45

Function of blood vessels

Answer 45

- arteries - transports blood from the heart to the arterioles under high pressure - arterioles - transports blood from the arteries to the capillaries - capillaries - site of exchange of materials between blood and tissue fluid - veins - transports blood from the capillaries back to the heart

Question 46

Explain how tissue fluid is formed and how it may be returned to the circulatory system (6)

Answer 46

1) as blood enters the capillaries the hydrostatic pressure of blood is high at arterial end of the capillary 2) causes water and soluble molecules pass out 3) large proteins and molecules remain 4) this lowers the water potential and hydrostatic pressure 5) water moves back into the venule end of the capillary by osmosis 6) lymphatic system absorbs any excess tissue fluid which returns to the circulatory system

Question 47

What is tissue fluid

Answer 47

Fluid containing water, glucose, amino acids, ions and oxygen which batches the tissues

Question 48

Properties of two key cells in the phloem tissue

Answer 48

1) sieve tube elements- are living cells with few organelles but no nucleus 2) companion cells - provide ATP for active transport f organic substances

Question 49

How does translocation occur - mass flow hypothesis

Answer 49

1) photosynthesis will occur in the chloroplast of the leaves creating organic substances e.g sucrose 2) Sucrose is actively transported from the source into the sieve tube elements using the ATP produced by the companion cell 3) This increase of sucrose in the sieve tube elements lowers the water potential 4) Water then moves into the sieve tube elements from the xylem vessels via osmosis 5) This increase in water volume in the sieve tube elements increase the hydrostatic pressure causing the liquid to be forced down to the sink 6) sucrose is used in respiration at the sink cell or stored as insoluble starch 7) more sucrose is actively transported in the sink cell causing the water potential to decrease 8) this results in osmosis of water from the sieve tube elements into the sink cell 9) the removal of water decreases the volume in sieve tube elements and therefore the hydrostatic pressure decreases

Question 50

What happens in the sink cells

Answer 50

Sucrose is used in respiration at the sink or stored mass insoluble starch

Question 51

Evidence/Investigations to show that sugars are transported in the phloem

Answer 51

- Tracers - Ringing experiment - aphids - as they feed on plants by penetrating the phloem and extracting the contents in the sieve tube elements

Question 52

How do tracers work

Answer 52

1) Plants are provided with only radioactively labelled carbon dioxide and over time this is absorbed into the plant and used in photosynthesis to create sugars which all contain the radioactively labelled carbon dioxide 2) Thin slices from the stems are then cut and placed on the x rays film and the stem that contains the sugars turn black and this highlights where the phloem is showing that the sugars are transported in the phloem

Question 53

How does the ringing experiment work

Answer 53

1) a ring of bark and phloem are removed off a tree trunk, resulting in the trunks to swell above the removed section 2) analysis of the liquid in this swelling shows it contains sugar, and this shows that when the phloem is removes the sugars cannot be transported and therefore proves that the phloem transports sugars

Question 54

Factors affecting transpiration

Answer 54

- Light intensity- increases rate of transpiration as more light will cause more stomata to open, which increases the surface area for the evaporation of water - temperature - increases rate of transpiration as more heat means faster kinetic energy, so faster moving molecules and therefore more evaporation - humidity - decreases rate of transpiration as more water vapour in the air means that the water potential outside is higher than inside the leaf therefore it reduces the water potential gradient so less evaporation occurs - wind - increases rate of transpiration as more wind will blow away the air containing the water vapour, maintaining the water potential gradient

Question 55

What are the factors that contribute to the cohesion tension theory (how water moves up the xylem)

Answer 55

- cohesion - adhesion - root pressure

Question 56

How does cohesion contribute to the cohesion tension theory

Answer 56

- water is dipolar which enables hydrogen bonds to form between the different water molecules, this creates cohesion between water molecules (they stick together) , therefore water travels up the xylem as a continuous water column

Question 57

How does adhesion (also known as capillarity) contribute to the cohesion tension theory

Answer 57

- Adhesion of water is when water sticks to other molecules and so the water adheres to the xylem walls - the narrower the xylem the bigger the impact of adhesion

Question 58

How does root pressure contribute to the cohesion tension theory

Answer 58

- as water moves into the root by osmosis it increases the volume of liquid inside the root and therefore the pressure inside the root increases, this is known as root pressure - this increase in pressure in the roots forces water above it upwards (positive pressure)

Question 59

Explain the cohesion tension theory (how water moves up the xylem)

Answer 59

1) Water vapour evaporates out of the stomata on leaves, this loss in water volume creates a lower pressure 2) when this water is lost by transpiration more water is pulled up the xylem to replace it (negative pressure) 3) due to hydrogen binds between the water molecules, the water molecules are cohesive, which creates a continuous column of water within the xylem 4) water molecules also adhere to the walls of the xylem, which helps pull the water column upwards 5) as this column of water is pulled up the xylem it creates tension, causing the xylem to be pulled inwards causing it to become more narrower, increasing the impact of adhesion

Question 60

How haemoglobin transports oxygen

Answer 60

1) Red blood cells contain haemoglobin, which has 4 haem groups. 2) In the capillaries in the lungs, oxygen binds to iron in haem groups forming oxyhaemoglobin. 3) Each haemoglobin molecule can carry 4 oxygen molecules, one per haem group. 4) Oxyhaemoglobin can be transported via blood to respiring body tissues. At body cells, oxygen dissociates from haemoglobin.

Question 61

describe the mechanism by which the arteriole regulates blood flow to capillaries

Answer 61

- smooth muscles within arteriole contracts - this contraction leads to the narrowing or constriction of arteriole lumen