module 3.2: transport in animals

Question 1

state one difference between fetal haemoglobin and adult haemoglobin and give one reason why this difference is essential to the fetus.
difference ……………………..
reason …………………….

Answer 1

• difference: (fetal haemoglobin) higher affinity for oxygen
  reason: (fetal haemoglobin) must be able to bind to oxygen, in low(er) partial pressure / in placenta / when adult oxyhaemoglobin dissociates / when adult haemoglobin dissociates from oxygen
• difference: (fetal haemoglobin) contains gamma sub-units
  reason: creates high(er) affinity for oxygen

Question 2

blood contains erythrocytes and neutrophils. tissue fluid may contain neutrophils but does not contain erythrocytes. tissue fluid is formed from plasma by pressure filtration through the capillary walls. all materials exchanged between the blood and cells pass through the capillary wall.
explain why tissue fluid does not contain erythrocytes

Answer 2

• gap(s) between endothelium cells (too) small
• (erythrocytes) too large / cannot change shape (much)
• to, fit / move / pass, between (endothelium) cells OR through, gaps / pores / fenestrations

Question 3

erythrocytes are full of haemoglobin.
describe the role of haemoglobin in transporting oxygen around the body

Answer 3

• (haemoglobin has) high affinity for oxygen
• oxygen binds to haemoglobin in, lungs / alveoli / high pO2
• forming oxyhaemoglobin
• oxygen released, in tissues / where needed / where pO2 is low / where respiration is occurring

Question 4

most carbon dioxide is transported as hydrogencarbonate ions in the plasma.
hydrogencarbonate ions are produced in the erythrocytes and diffuse into the plasma. describe how the hydrogencarbonate ions are produced in the erythrocytes

Answer 4

• carbon dioxide, enters / diffuses into, erythrocytes
• (carbon dioxide) combines / reacts, with water
• correct ref to carbonic anhydrase
• forms carbonic acid
• (carbonic acid) dissociates to form hydrogencarbonate ions and, hydrogen ions / protons

Question 5

high concentrations of carbon dioxide in the blood reduce the amount of oxygen transported by haemoglobin.
name this effect and explain why it occurs.
name …………………………….
explanation ………………………………..

Answer 5

• bohr (effect / shift)
• reduces affinity (of Hb) for oxygen
• formation of haemoglobinic acid / hydrogen ions interact with haemoglobin
• prevents, fall in pH / build-up of H+, in cells OR provides buffering effect
• alter, structure / shape, of haemoglobin
• more oxygen released where, needed / more respiration / carbon dioxide concentration high
• CO2 binds to haemoglobin forming carbaminohaemoglobin

Question 6

outline two conclusions that could be drawn from the data in Table 6.1 about the effects of smoking on lung cancer or CHD

Answer 6

• death from , CHD / lung cancer / both , increased (in smokers)
• CHD has bigger increase in number (of deaths) due to smoking (than lung cancer)
• lung cancer has bigger , relative / percentage , increase (in deaths) due to smoking (than CHD)