3.4.1 Mass Transport in Animals

Question 1

describe the role of red blood cells & haemoglobin (Hb) in oxygen transport

Answer 1

● red blood cells contain lots of Hb
○ no nucleus & biconcave → more space for Hb, high SA:V & short diffusion distance
● Hb associates with / binds / loads oxygenat gas exchange surfaces (lungs) where partial
pressure of oxygen (pO2) is high
● this forms oxyhaemoglobin which transports oxygen
○ each can carry four oxygen molecule, one at each haem group
● Hb dissociates from / unloads oxygen near cells / tissues where pO2 is low

Question 2

describe the structure of haemoglobin

Answer 2

-protein with a quaternary structure
-made of 4 polypeptide chains
-each chain contains a haem group containing an iron ion (Fe2+)

Question 3

define the haemoglobins

Answer 3

-a group of chemically similar molecules found in many different organisms

Question 4

describe the loading, transport and unloading of oxygen in relation to the
oxyhaemoglobin dissociation curve in areas of low pO2

Answer 4

-Hb has a low affinity for oxygen
-so oxygenreadily unloads / dissociates with Hb
-so % saturation is low

Question 5

describe the loading, transport and unloading of oxygen in relation to the
oxyhaemoglobin dissociation curve in areas of high pO2

Answer 5

-Hb has a high affinity for oxygen
-so oxygen readily loads / associates with Hb
-so % saturation is high

Question 6

name areas with low pO2

Answer 6

respiring tissues

Question 7

name areas with high pO2

Answer 7

gas exchange surfaces

Question 8

explain how the cooperative nature of oxygen binding results in an S-shaped (sigmoid) oxyhaemoglobin dissociation curve

Answer 8

1. binding of first oxygen changes tertiary / quaternary structure of haemoglobin
2. this uncovers haem group binding sites, making further binding of oxygens easier

Question 9

describe evidence for the cooperative nature of oxygen binding

Answer 9

● a low pO2 as oxygen increases there is little / slow increase in % saturation of Hb with oxygen
○ when first oxygen is binding
● at higher pO2, as oxygen increases there is a big / rapid increase in % saturation of Hb with oxygen
○ showing it has got easier for oxygens to bind

Question 10

what is the Bohr effect?

Answer 10

-effect of CO2 concentration on dissociation of oxyhaemoglobin → curve shifts to right

Question 11

explain effect of CO2 concentration on the dissociation of oxyhaemoglobin

Answer 11

1. increasing blood CO2 eg. due to increased rate of respiration
2. lowers blood pH (more acidic)
3. reducing Hb’s affinity for oxygen as shape / tertiary / quaternary structure changes slightly
4. so more / faster unloading of oxygen to respiring cells at a given pO2

Question 12

explain the advantage of the Bohr effect (eg. during exercise)

Answer 12

-more dissociation of oxygen → faster aerobic respiration / less anaerobic respiration → more ATP produced

Question 13

explain why different types of haemoglobin can have different oxygen
transport properties

Answer 13

-different types of Hb are made of polypeptide chains with slightly different amino acid sequences
-resulting in different tertiary / quaternary structures / shape
-so they have different affinities for oxygen

Question 14

explain how organisms can be adapted to their environment by having different types of haemoglobin with different oxygen transport properties (having high O2 affinity)

Answer 14

-more O2 associates with Hb more readily
-at gas exchange surfaces where pO2 is lower
-eg. organisms in low O2 environments - high
altitudes, underground, or foetuses
-curve shifts left

Question 15

explain how organisms can be adapted to their environment by having
different types of haemoglobin with different oxygen transport properties (having low O2 affinity)

Answer 15

-more O2 dissociates from Hb more readily
-at respiring tissues where more O2 is needed
-eg. organisms with high rates of respiration / metabolic rate (may be small or active)
-curve shifts right

Question 16

describe the general pattern of blood circulation in a mammal

Answer 16

closed double circulatory system - blood passes through heart twice for every circuit around body:
1. deoxygenated blood in right side of heart pumped to lungs; oxygenated returns to left side
2. oxygenated blood in left side of heart pumped to rest of body; deoxygenated returns to right

Question 17

suggest the importance of a double circulatory system

Answer 17

● prevents mixing of oxygenated / deoxygenated blood
○ so blood pumped to body is fully saturated with oxygen for aerobic respiration
● blood can be pumped to body at a higher pressure (after being lower from lungs)
○ substances taken to / removed from body cells quicker / more efficiently

Question 18

name the blood vessels entering and leaving the heart and lungs

Answer 18

● vena cava – transports deoxygenated blood from respiring body tissues →heart
● pulmonary artery -
transports deoxygenated blood from heart → lungs
● pulmonary vein – transports oxygenated blood from lungs → heart
● aorta – transports oxygenated blood from heart → respiring body tissues

Question 19

name the blood vessels entering and leaving the kidneys

Answer 19

-renal arteries – oxygenated blood → kidneys
-renal veins – deoxygenated blood to vena cava from kidneys

Question 20

name the the blood vessels that carry oxygenated blood to the heart muscle

Answer 20

-coronary arteries - located on surface of the heart, branching from aorta

Question 21

suggest why the wall of the left ventricle is thicker than that of the right

Answer 21

-thicker muscle to contract with greater force
-to generate higher pressure to pump blood around entire body

Question 22

explain the pressure & volume changes and associated valve movements
during the cardiac cycle that maintain a unidirectional flow of blood (atrial systole)

Answer 22

● atria contract
● so their volume decreases,
pressure increases
● atrioventricular valves open
when pressure in atria
exceeds pressure in ventricles
● semilunar valves remain shut as pressure in arteries
exceeds pressure in ventricles
● so blood pushed into
ventricles

Question 23

explain the pressure & volume changes and associated valve movements
during the cardiac cycle that maintain a unidirectional flow of blood (diastole)

Answer 23

● atria & ventricles relax
● so their volume increases,
pressure decreases
● semilunar valves shut when
pressure in arteries exceeds
pressure in ventricles
● atrioventricular valves open
when pressure in atria
exceeds pressure in ventricles
● so blood fills atria via veins & flows passively to ventricles

Question 24

explain the pressure & volume changes and associated valve movements
during the cardiac cycle that maintain a unidirectional flow of blood (ventricular systole)

Answer 24

● ventricles contract
● so their volume decreases,
pressure increases
● atrioventricular valves shut
when pressure in ventricles
exceeds pressure in atria
● semilunar valves open when pressure in ventricles exceeds pressure in arteries
● so blood pushed out of heart through arteries

Question 25

1. explain how graphs showing pressure or volume changes during the cardiac cycle (semilunar valves closed) can be interpreted

Answer 25

-pressure in [named] artery higher than in ventricle -to prevent backflow of blood from artery to ventricles

Question 26

2. explain how graphs showing pressure or volume changes during the cardiac cycle (semilunar valves open) can be interpreted

Answer 26

-when pressure in ventricle is higher than in [named] artery -so blood flows from ventricle to artery

Question 27

3. explain how graphs showing pressure or volume changes during the cardiac cycle (atrioventricular valves closed) can be interpreted

Answer 27

-pressure in ventricle higher than atrium -to prevent backflow of blood from ventricles to atrium

Question 28

4. explain how graphs showing pressure or volume changes during the cardiac cycle (atrioventricular valves open) can be interpreted

Answer 28

-when pressure in atrium is higher than in ventricle -so blood flows from atrium to ventricle

Question 29

how can heart rate be calculated from cardiac cycle data?

Answer 29

heart rate (beats per minute) = 60 (seconds) / length of one cardiac cycle (seconds)

Question 30

describe the equation for cardiac output

Answer 30

cardiac output (volume of blood pumped out of heart per min) = stroke volume (volume of blood pumped in each heart beat) x heart rate (number of beats per min)

Question 31

describe the function of arteries

Answer 31

-carry blood away from heart at high pressure

Question 32

explain how the structure of arteries relates to their function

Answer 32

●thick smooth muscle tissue -can contract and control / maintain / withstand blood flow / pressure ●thick elastic tissue -can stretch as ventricles contract and recoil as ventricles relax, to reduce pressure surges / even out blood pressure / maintain high pressure ●thick wall -withstands high pressure / prevents bursting ●smooth / folded endothelium -reduces friction / can stretch ●narrow lumen -increases / maintains high pressure

Question 33

describe the function of arterioles

Answer 33

-division of arteries to smaller vessels which can direct blood to different capillaries / tissues

Question 34

explain how the structure of arterioles relates to their function

Answer 34

● thicker smooth muscle layer than arteries ○ contracts → narrows lumen (vasoconstriction) → reduces blood flow to capillaries ○ relaxes → widens lumen (vasodilation) → increases blood flow to capillaries ● thinner elastic layer → pressure surges are lower (as further from heart /ventricles)

Question 35

describe the function of capillaries

Answer 35

-allow efficient exchange of substances between blood and tissue fluid (exchange surface)

Question 36

explain how the structure of capillaries relates to their function

Answer 36

●wall is a thin (one cell) layer of endothelial cells - reduces diffusion distance ●capillary bed - large network of branched capillaries -increases surface area for diffusion ●small diameter / narrow lumen -reduces blood flow rate so more time for diffusion ●pores in walls between cells -allow larger substances through

Question 37

describe the function of veins

Answer 37

-carry blood back to heart at lower pressure

Question 38

explain how the structure of veins relates to their function

Answer 38

● wider lumen than arteries → less resistance to blood flow ● very little elastic and muscle tissue → blood pressure lower ● valves → prevent backflow of blood

Question 39

explain the formation of tissue fluid

Answer 39

at the arteriole end of capillaries: 1. higher blood / hydrostatic pressure inside capillaries (due to contraction of ventricles) than tissue fluid (so net outward force) 2. forcing water (and dissolved substances) out of capillaries 3. large plasma proteins remain in capillary

Question 40

explain the return of tissue fluid to the circulatory system

Answer 40

at the venule end of capillaries: 1. hydrostatic pressure reduces as fluid leaves capillary (also due to friction) 2. (due to water loss) an increasing concentration of plasma proteins lowers water potential in capillary below that of tissue fluid 3. water enters capillaries from tissue fluid by osmosis down a water potential gradient 4. excess water taken up by lymph capillaries and returned to circulatory system through veins

Question 41

suggest and explain causes of excess tissue fluid accumulation

Answer 41

● low concentration of protein in blood plasma ○ water potential in capillary not as low → water potential gradient is reduced ○ so more tissue fluid formed at arteriole end / less water absorbed at venule end by osmosis ○ lymph system may not be able to drain excess fast enough ● high blood pressure (eg. caused by high salt concentration) → high hydrostatic pressure ○ increases outward pressure from arteriole end AND reduces inward pressure at venule end ○ so more tissue fluid formed at arteriole end / less water absorbed at venule end by osmosis ○ lymph system may not be able to drain excess fast enough

Question 42

what is a risk factor?

Answer 42

-an aspect of a person’s lifestyle or substances in a person’s body / environment -that have been shown to be linked to an increased rate of disease

Question 43

examples of risk factors for cardiovascular disease

Answer 43

-examples - age, diet high in salt or saturated fat, smoking, lack of exercise, genes