7.1 Haemoglobin

Question 1

What level protein structure does haemoglobin consist of

What type of protein is it

Answer 1

. Quaternary

Globular proteins

Question 2

Describe the primary structure of haemoglobin

Answer 2

. Sequence of amino acids in the four polypeptide chains

Question 3

Describe secondary structure of haemoglobin

Answer 3

Each of these polypeptide chains are coiled in a helix

Question 4

Describe tertiary structure of haemoglobin

Answer 4

. Each polypeptide chain is folded into a precise shape, which is an important factor for transporting oxygen

Question 5

Describe quaternary structure of haemoglobin

Answer 5

. 4 polypeptide chains are linked together to form an almost spherical molecule (2 alpha chains and 2 beta chains)
. Each polypeptide is associated with a haem group, which contains a ferrous (fe2+ ion)
Each Fe2+ ion can combine with a single oxygen molecule (O2)

As a result, a total of 4 oxygen molecules can be carried per haemoglobin in humans

Question 6

What is loading/associating in terms of haemoglobin and oxygen

Where does this take place in humans

Answer 6

. When haemoglobin binds with oxygen

So you may say the oxygen is associated with the haemoglobin

. Takes place in the lungs

Question 7

What is unloading/dissociating in terms of oxygen and haemoglobin

Where does this take place in humans

Answer 7

. Process by which haemoglobin releases its oxygen

Takes place in tissues

Question 8

What would haemoglobin with a high affinity for oxygen do

Answer 8

. This means they can take up oxygen more easily, but they release it less easily

Think of it as them being attracted to eachother

Question 9

What would haemoglobin with a low affinity for oxygen do

Answer 9

. It would take up oxygen less easily, and release it more easily

Question 10

What is the role of haemoglobin, and how is it adapted for it

Answer 10

. Its role is to transport oxygen
To be efficient at it:

. Haemoglobin must readily associate with oxygen at the surface where gas exchange occurs (eg lungs)

. Haemoglobin must readily dissociate from oxygen at those tissues requiring it

Question 11

How is haemoglobin able to associate with oxygen easily at lungs, but also dissociate it easily at tissue

What is the name of this effect

Answer 11

. Haemoglobin changes its affinity (chemical attraction) for oxygen under different conditions

. It achieves this by changing its shape in the presence of substances eg CO2

. In the presence of carbon dioxide, the new shape of the haemoglobin molecule binds more loosely to oxygen so it is dissociated easily at the tissues.

The Bohr affect

Question 12

What is the oxygen and carbon dioxide concentration like on a gas exchange surface eg lungs

What about in respiring tissues

Answer 12

Oxygen concentration is high on gas exchange surface
But CO2 concentration is low at gas exchange surface

However oxygen concentration is low in respiring tissues
But CO2 concentration is high at respiring tissues

Question 13

Why do different organisms have different haemoglobins

Answer 13

. Each species have haemoglobin with a slightly different amino acid sequence
. So as a result the tertiary and quaternary structures are different in different species and hence different oxygen binding properties

Each some haemoglobin may have a high affinity to oxygen whilst some may have a low affinity