Haemoglobin

Question 1

What is haemoglobins

Answer 1

Are protein molecules with a quaternary structure that has evolved to make it efficient at loading oxygen under one set of conditions but unloading it under a different set of conditions

Question 2

What’s the structure of haemoglobin

Answer 2

Primary - sequence of amino acids in the four polypeptide chains

Secondary - in which each of these polypeptide chains is coiled into a helix

Tertiary- in which each polypeptide chain is folded into a precise shape - an important factor in its ability to carry oxygen

Quaternary- in which all 4 polypeptides are linked together to form an almost spherical molecule. Each polypeptide is associated with a haem group - which contains a ferrous Fe ion. Making a total of 4 O2 molecules that can be carried by a single haemoglobin molecule in humans

Question 3

What is loading (associating)

Answer 3

The process by which haemoglobin binds with oxygen. Takes place in the lungs

Question 4

What is unloading (dissociating)

Answer 4

The process by which haemoglobin releases its oxygen

Takes place in the tissues

Question 5

What’s the difference between haemoglobins with a high affinity for oxygen and a low affinity for oxygen

Answer 5

High affinity - take up oxygen more easily, but release it less easily

Low affinity - take up oxygen less easily, but release it more easily

Question 6

The role of haemoglobin is to transport oxygen. Haemoglobin must do what to be efficient at transporting oxygen

Answer 6

Readily associate with oxygen at the surface where gas exchange takes place

Readily dissociate from oxygen at those tissues requiring it

Question 7

What’s the oxygen concentration, co2 concentration, affinity of haemoglobin for oxygen and result in the gas exchange surface

Answer 7

Oxygen concentration- high

Co2 conc- low

Affinity- high

Oxygen is associated

Question 8

What’s the oxygen concentration, co2 concentration, affinity of haemoglobin for oxygen and result in the respiring tissues

Answer 8

Oxygen concentration- low

Co2 conc- high

Affinity - low

Oxygen is dissociated

Question 9

Why do different haemoglobins have different affinities for oxygen

Answer 9

Each species has a slightly different amino acid sequence. The haemoglobin of each species therefore had a slightly different tertiary and quaternary structure and hence different oxygen binding properties