Topic 4.5 Transport of gases in the blood

Question 1

Describe the stucture of haemoglobin

Answer 1

Globular, water soluble. consists of four polypeptide chains, each carrying a haem group

Question 2

Describe the role of haemoglobin

Answer 2

Present in red blood cells. Oxygen molecules bind to the haem groups and are carried around the body to where they are needed in respiring tissues.

Question 3

How does partial pressure of oxygen affect oxygen-oxyhaemoglobin binding?

Answer 3

As partial pressure of oxygen increases, the affinity of haemoglobin for oxygen also increases, so oxygen binds tightly to haemoglobin. When partial pressure is low, oxygen is released from haemoglobin.

Question 4

Explain the Bohr effect

Answer 4

As partial pressure of CO₂ increases, the conditions become acidic causing haemoglobin to change shape. The affinity of haemoglobin for oxygen therefore decreases, so oxygen is released from haemoglobin.

Question 5

What do oxyhaemoglobin dissociation curves show?

Answer 5

Saturation of haemoglobin with oxygen (in %), plotted against ppO₂ in (kPa). Curves further to the left show the haemoglobin has a higher affinity for oxygen.

Question 6

How does the Bohr effect alter the position of an oxyhaemoglobin dissociation curve?

Answer 6

Curve shifts to the right because haemoglobin’s affinity for oxygen has decreased

Question 7

How does myoglobin differ from haemoglobin?

Answer 7

• Only has one haemgroup
• Has a very high affinity for oxygen even at low partial pressures
• Is found in muscle cells of animals with high metabolic demands

Question 8

How does foetal haemoglobin differ from adult haemoglobin?

Answer 8

The partial pressure of oxygen is low by the tie it reaches the foetus, therefore foetal haemoglobin has a higher affintiy for oxygen than adult. Allows both mother’s and child’s oxygen needs to be met.