Haemoglobin

Question 1

What is haemoglobin?

Answer 1

• Group of chemically similar molecules found in a wide variety of organisms

Question 2

How does the protein structure aid haemoglobin?

Answer 2

• Haemoglobins are protein molecules with a Quaternary structure that has evolved to make it efficient at loading oxygen under one set of conditions, but unloading under a different set of conditions

Question 3

What is the primary structure?

Answer 3

Sequence of amino acids in the four polypeptide chains

Question 4

What is the secondary structure?

Answer 4

• Sequence in which each of these polypeptide chains is coiled into a helix

Question 5

What is the tertiary structure?

Answer 5

• All four polypeptides are linked together to form an almost spherical molecule
• Each polypeptide is associated with a haem group which contains iron
• Each iron ion can combine with a single oxygen molecule, meaning a haemoglobin can carry a total of four oxygen molecules

Question 6

What gives haemoglobin its red colour?

Answer 6

Each chain having a haem group which contains an iron ion, which gives the haemoglobin its red colour

Question 7

What is formed when oxygen joins haemoglobin?

Answer 7

Oxyhaemoglobin

Question 8

What is loading oxygen?

Answer 8

• Process by which haemoglobin binds with oxygen

* In humans this occurs in the lungs

Question 9

What is unloading?

Answer 9

• Process by which haemoglobin releases its oxygen

* In humans this takes place at the tissues

Question 10

What is the role of haemoglobin?

Answer 10

• To transport oxygen

* Carried oxygen from the gas exchange surface to the tissues that required it for respiration

Question 11

What is required for haemoglobin to be efficient at transportation of oxygen?

Answer 11

Must be able to :
• Readily associate with oxygen at the surface where gas exchange takes place
• Readily dissociate from oxygen at those tissues requiring it

Question 12

How does affinity for oxygen change?

Answer 12

• Haemoglobin changes its affinity ( chemical attraction ) for oxygen under different conditions
• It achieves this because the shape changes in the presence of certain substances such as carbon dioxide
• In the presence of carbon dioxide new shape of the haemoglobin binds more loosely to oxygen

Question 13

Why does haemoglobin have different shapes?

Answer 13

• Haemoglobin of different species has a slightly different tertiary and Quaternary structure and therefore different oxygen binding properties
• Depending on its structure haemoglobin can range from a having a high affinity for oxygen to those that have a low affinity in oxygen

Question 14

How many oxygen molecules can join haemoglobin?

Answer 14

Four