3.2.8 transport of carbon dioxide

Question 1

carbonic anhydrase

Answer 1

enzyme that catalyses combination of carbon dioxide and water

Question 2

chloride shift

Answer 2

movement of chloride ions into erythrocytes to balance charge as hydrogen carbonate ions leave cell

Question 3

Bohr effect

Answer 3

effect that extra carbon dioxide has on haemoglobin, explaining release of more oxygen

Question 4

haemoglobinic acid

Answer 4

compound formed by buffering action of haemoglobin as combines with excess hydrogen ions

Question 5

describe the role of carbon dioxide in respiring tissues

Answer 5

1. respiring tissues with surplus carbon dioxide & les oxygen
2. waste products of respiration (carbon dioxide & water) catalysed by carbonic anhydrase forming carbonic acid (H2CO3)
3. carbonic acid dissociates into:
   - hydrogen ions which combine with haemoglobin forming haemoglobinic acid –> encourages oxyhaemoglobin to dissociate & gives respiring tissues oxygen
   - hydrogencarbonate ions (HCO3-) which removes CO2 from respiring tissues to blood & gets transported away

Question 6

where does high oxygen partial pressure occur

Answer 6

lungs

Question 7

where does low oxygen partial pressure occur

Answer 7

respiring tissues

Question 8

haemoglobin’s affinity for oxygen at low partial pressure

Answer 8

low affinity & will release oxygen

Question 9

haemoglobin’s affinity for oxygen at high partial pressure

Answer 9

high affinity for oxygen

Question 10

what is the Bohr effect

Answer 10

effect that increasing concentration of carbon dioxide has on haemoglobin

Question 11

describe the Bohr effect

Answer 11

1. carbon dioxide enters RBC forming carbonic acid, which dissociates forming hydrogen ions
2. hydrogen ions affect pH of cytoplasm = more acidic
3. change in pH affects tertiary structure of haemoglobin & reduces affinity for oxygen
4. oxyhaemoglobin dissociates

Question 12

why is more oxygen released when there’s a higher partial pressure of carbon dioxide in respiring tissues

Answer 12

more carbon dioxide = more hydrogen ions produced in RBC & causes oxyhaemoglobin to release more oxygen (dissociate)

Question 13

effect of carbon dioxide on saturation of haemoglobin (and describe difference on haemoglobin dissociation curve)

Answer 13

• more carbon dioxide = haemoglobin less saturated with oxygen
• haemoglobin dissociation curve shifts downwards & to right = Bohr shift