8.4 Transport Of O2 & CO2 in Blood

Question 1

What shape do erythrocytes have (Red blood cells)?

Answer 1

biconcave so there’s a larger SA for diffusion

Question 2

Where are erythrocytes made

Answer 2

in red bone marrow (adults)

Question 3

Why don’t erythrocytes have a nucleus

Answer 3

so there’s more space for haemoglobin and it limits their lifespan; they only last about 120 days in the bloodstream

Question 4

What is haemoglobin made up of

Answer 4

globular conjugated protein, 4 peptide chains, each with an iron-containing haem prosthetic group.

Question 5

How many bonds can haemoglobin make

Answer 5

can bond to 4 oxygen molecules

Question 6

What is the product of joining haemoglobin to oxygen

Answer 6

oxyhaemoglobin (reversible reaction)

Question 6

What is the product of joining haemoglobin to oxygen

Answer 6

oxyhaemoglobin (reversible reaction)

Question 7

What is positive cooperativity in joining oxygen to haemoglobin

Answer 7

When one oxygen binds, the haemoglobin changes shape so the other 3 oxygens can bind easier

Question 8

What happens when the oxygen-saturated haemoglobin travels to the cells

Answer 8

Because the oxygen levels in the cells is now lower than the oxygen in the erythrocytes, the oxygen easily moves down the concentration gradient to go into the cells.

Question 9

What do oxygen dissociation curves show

Answer 9

the affinity of haemoglobin for oxygen; on the axis are ‘% saturation of haemoglobin in the blood’ (Y-AXIS) and ‘partial pressure of oxygen’ (X-AXIS).

Question 10

What do results show in an oxygen dissociation curve

Answer 10

It increases steadily and rapidly because as soon as one oxygen binds, the other 3 rapidly bind after it, because the shape of haemoglobin changes to accommodate this addition; towards the end it levels off because the haemoglobin would be fully saturated and cannot bind to anymore oxygen

Question 11

Why is only 25% of oxygen released into cells when at rest

Answer 11

Because the demand is low so the body stores the rest as a reservoir for when demand suddenly increases

Question 12

What is the Bohr effect

Answer 12

When the partial pressure of CO2 rises, haemoglobin gives up oxygen more easily - known as the Bohr effect

Question 13

What happens as a result of the Bohr effect that makes it so important

Answer 13

1. haemoglobin gives up oxygen more readily in active tissues with a high partial pressure of CO2
2. in the lungs where the proportion of CO2 in the air is relatively low, oxygen binds to haemoglobin molecules more readily.

Question 14

Why must the foetus’ affinity for oxygen be much higher than the mother’s when in the womb

Answer 14

because it readily transfers oxygen into the baby’s deoxygenated blood from the mother’s oxygenated blood supply.

Question 15

What are the 3 ways CO2 is transported in the blood

Answer 15

1. 5% is dissolved in the plasma
2. 10-20% is combined with amino acids in polypeptide chains of haemoglobin to form carbaminohaemoglobin
3. 75-85% is converted into hydrogen carbonate ions in cytoplasm of RBCs

Question 16

What is formed when CO2 slowly reacts with water

Answer 16

carbonic acid —> this dissociates to form hydrogen ions and hydrogen carbonate ions.

Question 17

What enzyme is used to reverse the reaction back to carbonic acid

Answer 17

carbonic anhydrase (found in cytoplasm of RBCs) 
Using CO2 and water ---> carbonic acid the  dissociates to form carbonic ions and hydrogen ions.

Question 18

What is the chloride shift

Answer 18

When negatively charged hydrogen carbonate ions move out of the erythrocytes into the plasma by diffusion, down the conc. gradient. Chloride ions move back in to the erythrocytes, which maintains the electrical balance of the cell.

Question 19

What is haemoglobinic acid and how is it formed

Answer 19

haemoglobin in the erythrocytes reacts acts as a buffer and prevents changes in the in the pH by accepting free hydrogen ions in a reversible reaction to form HAEMOGLOBINIC ACID