3.4.1 - Mass transport in animals

Question 1

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 1

• Renal vein
• Vena cava to right atrium
• Right ventricle to pulmonary artery

Question 2

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 2

• (Plasma) proteins remain
• (Creates) water potential gradient / Reduces water potential (of blood)
• Water moves (to blood) by osmosis
• Returns (to blood) by lymphatic system

Question 3

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

Answer 3

• Muscle contracts
• Constricts/narrows arteriole/lumen

Question 4

Describe the advantage of the Bohr effect during intense exercise. (2)

Answer 4

• Increases dissociation of oxygen
  ‘accept unloading/ release/reduced affinity for dissociation’
• For aerobic respiration at the tissues/muscles/cells
  /Anaerobic respiration delayed at the tissues/muscles/cells
  /Less lactate at the tissues/muscles/cells

Question 5

EPO is another performance enhancing drug. It can increase the haematocrit (the percentage of red blood cells in blood). mA 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 5

• (EPO) causes blood to thicken
• (The thickened blood) could block the coronary arteries
  /(The thickened blood) slows blood flow
  /(The thicker blood) could cause clots;

Question 6

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

Answer 6

• Increases/more oxygen dissociation/unloading
  /Deceases haemoglobin’s affinity for O2
  ‘accept more readily/releases more O2
• (By) decreasing (blood) pH/increasing acidity

Question 7

Explain how the atrioventricuar valve maintains a unidirectional flow of blood. (2)

Answer 7

• Pressure in (left) atrium is higher than in ventricle/B causing valve to open
  /(When) pressure above valve is higher than below valve it opens
• Pressure in (left) ventricle/B is higher than in atrium causing valve to close
  /(When) pressure in below valve is higher than above valve it closes

Question 8

Name the blood vessels that carry blood to the heart muscle. (1)

Answer 8

• Coronary arteries

Question 9

Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind. Explain why. (2)

Answer 9

• Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin
  ‘accept conformational shift caused’
• Creates / leads to / uncovers second / another binding site
  / Uncovers another iron / Fe / haem group to bind to

Question 10

Explain the role of the heart in the formation of tissue fluid. (2)

Answer 10

• Contraction of ventricle(s) produces high blood / hydrostatic pressure
• (This) forces water (and some dissolved substances) out (of blood capillaries)

Question 11

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 11

• Excess tissue fluid cannot be (re)absorbed / builds up