Haemoglobin

Text p.150-1The haemoglobins are a group of chemically

similar molecules found in manydifferent organisms.

Haemoglobin is a protein with a quaternary structure.

Homework

• Text p.151 red2nd lesson• p.155 red• Find out about foetal haemoglobin – how

does a foetus gain oxygen from its mother? Present on A4 paper (oxygen dissociation graph and explanation)

Did you know?

• 1 litre of water can hold 25ml of oxygen• 1 litre of blood can carry 200ml.• THAT’S 8 TIMES AS MUCH.

Objectives

1. What are haemoglobins and what is their role?

2. How do haemoglobins from different organisms differ and why?

3. What is loading and unloading of oxygen?

4. What colour is haemoglobin compared to oxyhaemoglobin?

Haemoglobin

Each haem group can combine with one oxygen molecule, so that one molecule of haemoglobin can combine with a maximum of four oxygen molecules. This forms oxyhaemoglobin.

Haemoglobin is a protein making up 95% of the dry mass of a red blood cell. It is the means of transport of oxygen around the body.

polypeptide chain

Haemoglobin is made up of four polypeptide chains, each bound to one haem group.

Student modelling

• Use playdoh to make a haemoglobin molecule

Haemoglobin molecules p150

Questions

1. How would you describe ‘Haemoglobins’?

2. Explain how haemoglobin has each level of protein structure.

3. What is a haem group, and what does it do?

The haem group is known as a prosthetic group joined to the protein chain.

Haem unit

Structure of Haemoglobin

Primary• Sequence of amino acids in a poypeptide chainSecondary• In which each of these polypeptide chains is coiled into a

helix or pleated.Tertiary• In which each polypeptide chain is folded into a precise

shape – an important factor in it’s ability to carry oxygenQuaternary• In which all four polypeptides are linked together to form

an almost spherical molecule. Each unit is associated with a haem group (which contain Fe2+ that can combine with 1 O2 molecule). Total – 4 O2 molecules.

The Role of Haemoglobinp150-1

1. What 2 properties must haemoglobin have to be efficient at transporting oxygen?

2. How does haemoglobin achieve these 2 things?

3. Under what conditions does haemoglobin attach to oxygen?

4. Describe the conditions under which oxyhaemoglobin releases oxygen.

The Role of Haemoglobinp150-1

1. What 2 properties must haemoglobin have to be efficient at transporting oxygen?

2. How does haemoglobin achieve these 2 things?

3. Under what conditions does haemoglobin associates with oxygen?

4. Describe the conditions under which oxyhaemoglobin dissociates with oxygen.

1. Combine/associate with oxygen and dissociate or release oxygen

2. Hb changes its affinity for oxygen under different conditions because it changes its shape slightly

3. Associates more readily with oxygen when high conc. Oxygen (and low carbon dioxide)

4. Dissociates in the presence of high carbon dioxide (and low oxygen)

Different types of haemoglobin

Type of haemoglobin What it does Metabolic rate

Example of organism

(write in name)

High affinity for oxygen

Associates with oxygen easilyDissociates with oxygen less readily

Low in oxygen

Low affinity for oxygen

High in oxygen so doesn’t matter it is taken up less easily

High – oxygen is released readily into respiring tissues

Different types of haemoglobin

Type of haemoglobin What it does Environment

of organism Metabolic rate Example of organism

High affinity for oxygen

Associates with oxygen easilyDissociates with oxygen less readily

Low in oxygen Not very high so it doesn’t matter if oxygen isn’t released that readily

Lugworm

Low affinity for oxygen

Associates with oxygen less easily but dissociates more readily

High in oxygen so doesn’t matter it is taken up less easily

High – oxygen is released readily into respiring tissues

Pigeon/bird

Why do different Hbs have different affinities for

oxygen1. What did scientists find out about

different organisms haemoglobin?2. Why do they have different affinities

for oxygen?

Loading and unloading oxygen

• The process by which haemoglobin becomes oxyhaemoglobin is called … or …

• When oxyhaemoglobin loses oxygen it is called … or …

• Each haemoglobin molecule can combine with … oxygen molecules;

• Hb + 4O2 HbO8

Loading and unloading oxygen

• The process by which haemoglobin becomes oxyhaemoglobin is called loading or associating.

• When oxyhaemoglobin loses oxygen it is called unloading or dissociating.

• Each haemoglobin molecule can combine with four oxygen molecules;

• Hb (dark red) + 4O2 (bright red) HbO8

Key words

• Affinity• Associate/loading• Dissociate/unloading• More readily• Less readily• Saturated

Objectives

1. What are haemoglobins and what is their role?

2. How do haemoglobins from different organisms differ and why?

3. What is loading and unloading of oxygen?

4. What colour is haemoglobin compared to oxyhaemoglobin?