3.3.4 - MASS TRANSPORT IN ANIMALS

Question 1

the oxygen dissociation curve for haemoglobin shifts to the right during vigorous exercise.

explain the advantage of this shift (3)

Answer 1

1. lower affinity for oxygen/releases more oxygen/oxygen is released quicker/oxygen dissociates/unloads more readily
2. to muscles/tissues/cells
3. for high/rapid respiration

Question 2

high absorption of salt from a diet can result in a higher than normal concentration of salt in the blood plasma entering capillaries. this can lead to a build-up of tissue fluid.

explain how. (2)

Answer 2

ANY PAIR:

1. (higher salt) results in lower water potential of tissue fluid
2. so less water returns to capillary by osmosis (at venule end)

OR

3. (higher salt) results in higher blood pressure/volume
4. so more fluid pushed/forced out (at arteriole end) of capillary

Question 3

describe the advantage of the Bohr effect during intense exercise (2)

Answer 3

1. increases dissociation of oxygen/reduces affinity
2. for aerobic respiration at the muscles

Question 4

describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin (2)

Answer 4

1. increases oxygen dissociation OR decrease haemoglobin’s affinity for oxygen
2. by decreasing blood pH

Question 5

explain why binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind (2)

Answer 5

1. binding of first oxygen changes quaternary structure of haemoglobin
2. creates/uncovers another binding site

Question 6

give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs

do not include descriptions of pressure changes in the heart or the role of heart valves in your answer (3)

Answer 6

1. renal vein
2. vena cava to right atrium
3. right ventricle to pulmonary artery

Question 7

tissue fluid is formed from blood at the arteriole end of a capillary bed.

explain how water from tissue fluid is returned to the circulatory system (4)

Answer 7

1. plasma proteins remain
2. creates WP gradient OR reduces WP of blood
3. water moves to blood by osmosis
4. returns to blood by lymphatic system

Question 8

explain how an arteriole can reduce the blood flow into capillaries (2)

Answer 8

1. muscle contracts
2. narrows/constricts arteriole/lumen

Question 9

which of the following blood vessels carries blood at the lowest pressure? (1)

• capillary
• pulmonary vein
• renal vein
• vena cava

Answer 9

vena cava

Question 10

EPO is a performance-enhancing drug. it can increase the haematocrit (the % of RBC in blood)

a heart attack is caused by a lack of glucose and oxygen being delivered to cardiac muscle via the coronary arteries.

the overuse of EPO can increase the risk of a heart attack. suggest how. (2)

Answer 10

1. EPO causes blood to thicken
2. thickened blood could block coronary arteries OR slows blood flow OR could cause clots

Question 11

explain how the atrioventricular valves maintain a unidirectional flow of blood (2)

Answer 11

1. pressure in atrium is higher than in ventricle causing valve to open

OR

when pressure above valve is higher than below valve it opens

2. pressure in ventricle is higher than in atrium causing the valve to close

OR

when pressure below valve is higher than above valve, it closes

Question 12

name the blood vessels that carry blood is the heart muscle (1)

Answer 12

coronary arteries

Question 13

explain the role of the heart in the formation of tissue fluid (2)

Answer 13

1. contraction of ventricles produces high blood/hydrostatic pressure
2. this forces water (and some dissolved substances) out of blood capillaries

Question 14

lymphoedema is a swelling in the legs which may be caused by a blockage in the lymphatic system.

suggest how a blockage in the lymphatic system could cause lymphoedema (1)

Answer 14

1. excess tissue fluid cannot be reabsorbed
2. so it builds up

Question 15

explain how changes in the shape of haemoglobin result in a S-shaped (sigmoid) oxyhaemoglobin dissociation curve (2)

Answer 15

1. Hb has lower affinity for oxygen at low partial pressures
2. easier unloading of oxygen for aerobic respiration

Question 16

what is the function of the coronary arteries? (2)

Answer 16

1. carry oxygen/glucose
2. to heart/cardiac muscle/tissue/cells

Question 17

although the speed of blood flow in an arteriole is greater than speed of blood flow in a capillary, blood does not accumulate in the arterioles.

explain why. (1)

Answer 17

1. more capillaries than arterioles
2. so area of capillaries greater than arterioles

Question 18

other than causing slow blood flow, explain one advantage of capillaries being narrow (2)

Answer 18

1. short distance/pathway between blood and cells outside of the capillary
2. large surface area of blood in contact with walls of capillaries
3. fast diffusion

Question 18

what factor limits the minimum internal diameter of the lumen of a capillary? (1)

Answer 18

width/size/diameter of blood cell

Question 19

the volume of blood leaving the capillary network into the veins is less than the volume of blood entering from the arteries.

explain why. (1)

Answer 19

fluid in tissue fluid/fluid in lymph

Question 20

a principle of homeostasis is the maintenance of a constant internal environment. an increase in the concentration of carbon dioxide would change the internal environment and blood pH.

explain the importance of maintaining a constant blood pH. (3)

Answer 20

1. named protein/enzyme (haemoglobin) is affected by a change in pH
2. would result in change of shape/tertiary structure
3. described effect on protein/enzyme (so less oxygen will bind with haemoglobin)

Question 21

the hydrostatic pressure falls from the arteriole end of the capillary to the venule end of the capillary. explain why (1)

Answer 21

1. loss of water/fluid

OR

2. friction against capillary lining

Question 22

high blood pressure leads to an accumulation of tissue fluid. explain how (3)

Answer 22

1. high BP = high hydrostatic pressure
2. increases outward pressure from arterial end of capillary OR reduces inward pressure at venule end of capillary
3. so more tissue fluid formed/less tissue fluid is reabsorbed/lymph system not able to drain tissues fast enough

Question 23

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

explain why. (3)

Answer 23

1. water has left the capillary
2. proteins (in blood) too large to leave capillary
3. increasing/giving higher concentration of blood proteins and thus WP

Question 24

gas exchange for the fetus occurs in the placenta.

describe how the composition of blood in the pulmonary artery of a fetus is different from the composition of blood in the pulmonary artery of its mother.

give one reason for this difference (1)

Answer 24

1. fetal blood has more oxygen
2. because gas exchange occurs in the placenta

Question 25

name the type of blood vessel that controls blood flow to muscles and explain how these blood vessels change blood flow during exercise (3)

Answer 25

1. arteriole
2. circular/smooth muscle relaxes
3. vasodilation increases blood flow OR widens/dilates lumen of blood vessel so increases blood flow

Question 27

this virus causes damage to capillaries so that blood proteins move out of the capilaries into the tissue fluid.

explain how this would affect he return of tissue flid into the capillaries (2)

Answer 27

1. increases water potential of capillary OR decreases water potential of tissue fluid
2. so less water returns to capillaries by osmosis OR so more water leaves blood/capillaries by osmosis