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 oxygen at 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

What are the haemoglobins?

Answer 3

The haemoglobins are 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 (Areas withlowpO2 -respiring tissues)

Answer 4

● Hb has a low affinity for oxygen

● So oxygen readily 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 ( Areas with high pO2 - gas exchange surfaces)

Answer 5

● Hb has a high affinity for oxygen

● So oxygen readily loads/associates with Hb

● So % saturation is high

Question 6

Explain how the co-operative nature of oxygen binding results in an S-shaped (sigmoid) oxyhaemoglobin dissociation curve

Answer 6

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 6

Describe evidence for the co-operative nature of oxygen binding

Answer 6

● A low pO2 as oxygen increases there is little/slow increase in % saturation of Hb with oxygen
○ When first oxygen is binding

● AthigherpO2 ,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 7

What is the Bohr effect?

Answer 7

Effect of CO2 concentration on dissociation of oxyhaemoglobin → curve shifts to right

Question 8

Explain effect of CO2 concentration on the dissociation of oxyhaemoglobin

Answer 8

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 8

Graph to show the % saturation of Hb with oxygen against the partial pressure of oxygen

Answer 8

Question 9

Describe evidence for the Bohr effect

Answer 9

At a given pO2 %, the saturation of Hb with oxygen is lower

Question 10

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

Answer 10

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

Question 11

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

Answer 11

● 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 12

Explain how organisms can be adapted to their environment by having different types of haemoglobin with different oxygen transport
properties (curve shift left - Hb has higher affinity for O2)

Answer 12

Curve shift left - Hb has higher affinity for O2

● 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

Question 13

Explain how organisms can be adapted to their environment by having different types of haemoglobin with different oxygen transport
properties (curve shift right - Hb has lower affinity for O2)

Answer 13

Curve shift right - Hb has lower affinity for O2

● 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)

Question 14

Describe the general pattern of blood circulation in a mammal

Answer 14

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 15

What is a closed double circulatory system?

Answer 15

blood passes through heart twice for every circuit around body

Question 16

Suggest the importance of a double circulatory system

Answer 16

● 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 17

Draw a diagram to show the general pattern of blood circulation in a mammal, including the names of key blood vessels

Answer 17

Question 18

What does the vena cava do?

Answer 18

● Vena cava–transports deoxygenated
blood from respiring body tissues → heart

Question 19

What does the pulmonary artery do?

Answer 19

● Pulmonary artery–transports deoxygenated blood from heart → lungs

Question 20

What does the pulmonary vein do?

Answer 20

● Pulmonary vein–transports oxygenated
blood from lungs → heart

Question 21

What does the aorta do?

Answer 21

● Aorta–transports oxygenated blood
from heart → respiring body tissues

Question 22

Name the blood vessels entering and leaving the kidneys

Answer 22

● Renal arteries– oxygenated blood → kidneys

● Renal veins–deoxygenated blood to vena
cava from kidneys

Question 23

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

Answer 23

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

Question 24

Label a diagram to show the gross structure of the human heart (inside)

Answer 24

Question 25

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

Answer 25

● Thicker muscle to contract with greater force ● To generate higher pressure to pump blood around entire body

Question 26

What happens during atrial systole?

Answer 26

● 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 27

What happens during ventricular systole?

Answer 27

● Ventricles contract ● So their volume decreases, pressure increases ● Atrioventricular valves shut when pressure in ventricles exceeds pressure in atria ● Semi lunar valves open when pressure in ventricles exceeds pressure in arteries ● So blood pushed out of heart through arteries

Question 28

What happens during diastole?

Answer 28

● Atria & ventricles relax ● So their volume increases, pressure decreases ● Semi lunar 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 29

Explain how graphs showing pressure or volume changes during the cardiac cycle can be interpreted, eg.to identify when valves are open/closed

Answer 29

Question 30

Semi lunar valves closing meaning

Answer 30

● Pressure in [named] artery higher than in ventricle ● To prevent back flow of blood from artery to ventricles

Question 31

Semi lunar valves open meaning

Answer 31

● When pressure in ventricle is higher than in [named] artery ● So blood flows from ventricle to artery

Question 32

Atrioventricular valves closed meaning

Answer 32

● Pressure in ventricle higher than atrium ● To prevent back flow of blood from ventricles to atrium

Question 33

Atrioventricular valves open meaning

Answer 33

● When pressure in atrium is higher than in ventricle ● So blood flows from atrium to ventricle

Question 34

How can heart rate be calculated from cardiac cycle data?

Answer 34

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

Question 35

Describe the equation for cardiac output

Answer 35

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 36

What is the function of the arteries?

Answer 36

Function–carry blood away from heart at high pressure

Question 37

Explain how the structure of arteries relates to their function

Answer 37

- 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 38

Explain how the structure of arterioles relates to their function

Answer 38

● 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 39

What is the function of the arterioles?

Answer 39

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

Question 40

Explain how the structure of capillaries relates to their function

Answer 40

- 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 41

What is the function of the capillaries?

Answer 41

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

Question 42

Explain how the structure of veins relates to their function

Answer 42

● Wider lumen than arteries → less resistance to blood flow ● Very little elastic and muscle tissue→ blood pressure lower ● Valves→ prevent back flow of blood

Question 43

What is the function of the veins?

Answer 43

Function – carry blood back to heart at lower pressure

Question 44

Explain the formation of tissue fluid at the arteriole end of capillaries

Answer 44

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 45

Explain the return of tissue fluid to the circulatory system at the venule end of the capillaries

Answer 45

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 46

Suggest and explain causes of excess tissue fluid accumulation

Answer 46

● 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 47

What is a risk factor? Give examples for cardiovascular disease

Answer 47

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