section 2. (2) explain the adaptive advantage of haemoglobin

Question 1

What is haemoglobin?

Answer 1

• Haemoglobin is a protein molecule containing iron- which is what gives blood its red colour
• Made of 4 polypeptide chains called globins which are joined to a haem group (containing iron)

Question 2

How many units of oxygen can haemoglobin carry per molecule?

Answer 2

• One molecule of haemoglobin can carry 4 units of oxygen: one molecule of haem connects to one unit of oxygen

Question 3

What happens to haemoglobin once oxygen is added?

Answer 3

• Haemoglobins ability to join with oxygen increases as more oxygen is added: Addition of oxygen alters the haemoglobin molecules chape a little bit so that each subsequent bond is easier

Question 4

What is the main adaptive advantage of haemoglobin?

Answer 4

Haemoglobin is able to increase the oxygen-carrying capacity of blood. Due to the fact that each haemoglobin molecule contains 4 haem units, each molecule can bond to 4 oxygen molecules at once. Hence much more oxygen can be transported around the blood in haemoglobin, rather than being dissolved in plasma.

Question 5

What is an adaptive advantage that arises form haemoglobins increased ability to attach oxygen when oxygen is added?

Answer 5

The bonding of each oxygen molecule slightly alters the shape of the haemoglobin, making it easier for subsequent molecules to bind to it. This increases the rate and efficiency of oxygen uptake. As a result, a small increase in oxygen concentration at the lungs results in a large increase in oxygen saturation in the blood. For example during exercise.

Question 6

What happens to haemoglobin in the presence of carbon dioxide?

Answer 6

Another advantage is that haemoglobin’s capacity to release oxygen increases in the presence of carbon dioxide. Metabolizing cells produce carbon dioxide, which combines with water to form carbonic acid, which lowers the pH. Haemoglobin has a lower affinity for oxygen at a lower pH, as a result, oxygen is released in areas where it is needed (metabolizing cells)

Question 7

how come haemoglobin doesn’t impact the osmotic balance of blood plasma?

Answer 7

The fact that haemoglobin is enclosed inside red blood cells, means that it doesn’t disturb the osmotic balance of the blood plasma.