3.3.4.1 Mass transport in animals

Question 1

Describe and explain the structure of haemoglobin

Answer 1

• quaternary protein structure with 4 polypeptide chains
• associated with a prosthetic group called haem

Question 2

How is haemoglobin able to bind to oxygen?

Answer 2

• each of the 4 polypeptides has a haem group
• containing an iron ion
• which binds to oxygen

Question 3

Haemoglobin and oxygen equation

Answer 3

Haemoglobin + oxygen <–> oxyhaemoglobin
—> loading in lungs
<— unloading at respiring tissue

Question 4

How is haemoglobin able to transport oxygen effectively?

Answer 4

• readily associate with oxygen at lungs
• readily dissociate from oxygen at respiring tissue

Question 5

Why is the oxyhaemoglobin dissociation curve S-shaped?

Answer 5

• binding of first oxygen changes tertiary structure of haemoglobin
• uncovers another iron binding site
• allows more oxygen to bind
• cooperative binding

Question 6

Why does the oxygen dissociation curve shift left?

Answer 6

• haemoglobin has a higher affinity for oxygen
• loads more oxygen more readily (unloads less readily)
• haemoglobin more saturated with oxygen at a lower partial pressure of oxygen

Question 7

Examples of when the oxygen dissociation curve shifts left

Answer 7

• Low partial pressure of oxygen environment
• Higher altitude/ underwater
• Haemoglobin of/foetus/lugworm
• Myoglobin

Question 8

Examples of when the oxygen dissociation curve shifts right

Answer 8

• higher pCO2 (partial pressure of carbon dioxide) - fish swimming
• higher metabolic rate - bird in flight, mouse

Question 9

How does excess carbon dioxide create acidic conditions?

Answer 9

• Dissolves in blood plasma and cytoplasm in cells
• Produces carbonic acid

Question 10

Why is the foetal haemoglobin curve shifted to the left?

Answer 10

• Foetal haemoglobin has a higher affinity for oxygen
• So foetal haemoglobin loads more oxygen more readily
• From mother’s blood to foetal blood (across placenta)

Question 11

Why is the mouse haemoglobin curve shifted to the right?

Answer 11

• haemoglobin has a lower affinity for oxygen
• So haemoglobin unloads more oxygen more readily to respiring tissue to be used for respiration

Question 12

Describe myoglobin?

Answer 12

• very high affinity for oxygen
• found in muscle cells
• act as oxygen reserved

Question 13

Why are the coronary arteries important?

Answer 13

• to supply the heart muscle cells (cardiomyocytes)
• with oxygen
• and glucose
• for aerobic respiration
• to release energy
• for muscle contraction

Question 14

Explain how the structures of the walls of arteries and arterioles are related to their functions

Answer 14

• elastic tissue stretches at high pressure and recoils at low pressure
• to even out pressure flow
• muscle contracts to reduce diameter of lumen/vasoconstriction
• to change the bloodflow or pressure
• thick muscular wall withstands pressure and stops bursting
• endothelium is smooth
• to reduce friction

Question 15

Describe and explain how the structure of a capillary adapts for the exchange of substances between blood and surrounding tissue

Answer 15

• permeable capillary wall
• single cell thick, reduces diffusion distance
• flattened endothelial cells, reduces diffusion distance
• fenestrations, allows large molecules through
• narrow lumen, reduces rate of bloodflow so more time for diffusion
• Small diameter/ narrow, large surface area: volume ratio
• red blood cells in contact with wall/ pass singly, more time for diffusion

Question 16

Explain how fluid leaves the capillary at the arterial end

Answer 16

• High hydrostatic pressure of the blood at the arterial end (greater than osmotic effect)
• So it forces water and soluble molecules out of the capillary- ultrafiltration
• but large proteins and molecules remain

Question 17

Explain how tissue fluid is returned to the circulatory system

Answer 17

• Large proteins remain in blood so
• there is a lower water potential in capillaries at venous end
• So water moves back into venous end of capillary
• by osmosis
• excess tissue fluid is also returned by the lymph system
• and returns tissue fluid to the blood at the vena cava

Question 18

Describe and explain two ways in which the composition of tissue fluid differs from the blood plasma in the capillaries

Answer 18

• tissue fluid contains no large proteins because these molecules are too large no pass through capillary wall
• tissue fluid contains less glucose because some will have entered tissue cells

Question 19

Name 6 substances that are at a higher concentration in the blood plasma at the arteriole end than the venous end

Answer 19

• oxygen
• glucose
• amino acids
• minerals
• fatty acids
• glycerol

Question 20

How is water from the lymph returned to the blood?

Answer 20

• via the lymphatic system
• due to hydrostatic pressure and muscle contraction

Question 21

Explain how fluid leaves the capillary at the arterial end

Answer 21

• hydrostatic pressure
• greater than osmotic effect
• forces molecules out

Question 22

What are the names of valves present in the heart?

Answer 22

Semilunar (leaving ventricles)
Atrioventricular (between atria and ventricles)

Question 23

Describe and explain events of the cardiac cycle

Answer 23

• during the atrial systole the atria contract
• volume decreases and pressure increases in atria
• atrioventricular valves open because pressure is higher in atria than ventricles
• during the ventricular systole the ventricles contract
• volume decreases and pressure increases in ventricles
• atrioventricular valves close because pressure is higher in ventricles than atria
• semilunar valves open because pressure is higher in ventricles than aorta/pulmonary artery
• during diastole both atria and ventricles relax
• semilunar valves close - pressure higher in aorta /pulmonary artery than ventricles
• atrioventricular valves open - heart fills with blood

Question 24

Explain how the heart valves maintain a one way flow of blood from left atrium to the aorta

Answer 24

• atrium has higher pressure than ventricle (due to filling/contraction)
• atrioventricular valves open
• ventricle has higher pressure than atrium (due to filling/contraction)
• atrioventricular valve closes
• ventricle has higher pressure than aorta
• semilunar valve opens
• higher pressure in aorta than ventricle (as heart relaxes)
• muscle contraction causes increase in pressure

Question 25

Why does the left ventricle have the thickest muscular wall?

Answer 25

• more powerful contraction
• to generate more pressure
• to pump blood further around the body

Question 26

What artery and vein are connected to the kidneys?

Answer 26

Renal

Question 27

How is the Bohr effect useful during intense excercise?

Answer 27

• increases dissociation of oxygen
• for aerobic respiration at respiring tissue

Question 28

What is the bohr effect?

Answer 28

• changes in oxygen dissociation curve as a result of change in carbon dioxide levels
• when partial pressure of carbon dioxide in the blood is high, haemoglobin has a lower affinity for oxygen

Question 29

Explain how haemoglobin has a lower affinity for oxygen at respiring tissue

Answer 29

• co2 produced as waste product of respiration
• co2 dissolves in blood plasma to form carbonic acid, which lowers pH of blood
• carbonic acid dissociates into hydrogen and carbonate ions
• hydrogen ions bind to haemoglobin, causing the release of oxygen

Question 30

What blood vessel delivers blood to muscles? How does it change during excersise?

Answer 30

• arteriole
• Muscle relaxes
• vasodilation increases blood flow - wider lumen