Haemoglobin

Question 1

SA:Vol ratio of larger organisms?

Answer 1

Smaller

Question 2

Why is simple diffusion not sufficient for larger organisms?

Answer 2

Smaller SA:Vol ratio and too large of a diffusion distance so need more specialised exchange systems.

Question 3

How many polypeptide subunits does a haemoglobin molecule contain?

Answer 3

4

Question 4

Where does haemoglobin readily associate and dissociate?

Answer 4

Associates at gas exchange surface (lungs) and dissociates at respiring tissue/cells

Question 5

What is oxyhaemoglobin reversible reaction?

Answer 5

Hb + O2 <–> Hb(O2)4

Question 6

Percentage saturation formula of haemoglobin with oxygen

Answer 6

(Oxygenated haemoglobin / Max. saturation) x 100

Question 7

Define PO2

Answer 7

The proportion of oxygen in a mixture of gases or a solution

Question 8

Relationship between PO2 and haemoglobin

Answer 8

Higher PO2 = more haemoglobin saturated as more oxygen available to be readily associated

Question 9

Why is it easier for 2nd and 3rd oxygen to bind to haemoglobin?

Answer 9

First oxygen molecule exposes 2nd and 3rd bases by altering specific tertiary structure of haemoglobin by stressing bonds. Easier and readier to associate.

Question 10

Relationship between pCO2 and haemoglobin saturation

Answer 10

As pCO2 increases, haemoglobin saturation decreases. Causes dissociation curve to shift to the RIGHT

Question 11

What is bohr shift

Answer 11

Increased pCO2 levels causes decrease in hb saturation and a sigmoidal shift to the right.

Question 12

Why is higher CO2 concentration in the blood bad?

Answer 12

When CO2 dissolves in the blood it makes it more acidic, thus lowering the pH. As hb is a protein, a change in pH can alter the tertiary structure. (Lower affinity to O2 at higher CO2 levels)

Question 13

Heat from respiration helps mammals maintain a constant body temperature. Explain the relationship between the SA:Vol ratio of mammals and the O2 dissociation curves of their haemoglobins.

Answer 13

• Smaller mammal has larger SA:Vol ratio.
• Smaller mammal has more heat loss (per unit of body mass)
• Smaller mammal has greater metabolic rate.
• O2 required for aerobic respiration so hb releases more oxygen (lower affinity)

Question 14

How many types of basic haemoglobin?

Answer 14

3
- Adult humans/ sea level organisms
- Lower pO2 environment (shift to left)
- Higher metabolic rate animals (shift to right. Hb has lower affinity to O2)

Question 15

The oxygen dissociation curve of a foetus is that to the left of its mother. Explain the advantage of this for the foetus.

Answer 15

• Hb has higher affinity for O2
• At lower pO2
• As oxygen moves from mother to foetus