One blood cell contains about 280 million molecules of haemoglobin

What is this?

Lesson Objectives(E) What are haemoglobins and what is their

role? (C) How do haemoglobins from different

organisms differ and why?(C) What is loading and unloading of oxygen? 

Haemoglobin•Globular protein.•Quarternary structure.•Two alpha + 2 beta chains.•Haem group at centre of each tertiary structure (contains a ferrous ion Fe2+).

                            

  

• Each haem group carries one molecule of O2.

• SoHb + 4O2 HbO8

oxyhaemoglobin• To be efficient haemoglobin must

– Readily pick up O2 at the gas exchange surface.– Readily release O2 at those tissues requiring it.

Hypochromic Anemia

What happens if we have an iron deficiency?

Complete the table by adding high or low to the blanks

Region of body

Oxygen concentration

Carbon dioxide

concentration

Affinity of haemoglobin for oxygen

Result

Gas exchange surface

Oxygen is attached

Respiring tissues

Oxygen is released

Affinity of haemoglobin under different conditions

Affinity of haemoglobin under different conditionsRegion of body

Oxygen concentration

Carbon dioxide concentration

Affinity of haemoglobin for oxygen

Result

Gas exchange surface

High Low High Oxygen is attached

Respiring tissues

Low High Low Oxygen is released

Different Haemoglobins

• Different organism have different haemoglobins, this depends upon the organisms metabolism and environment.– Haemoglobins with a high affinity for oxygen.

These take up oxygen more easily but release it less readily

– Haemoglobins with a low affinity for oxygen. These take up oxygen less readily but release it more readily

What animals do you think would have a haemoglobin with a

high affinity for oxygen?

And a low affinity for oxygen?

Lesson Objectives(E) What is an oxygen dissociation curve?(C) What is the effect of carbon dioxide on the curve and why?(A/B) How do the properties of the haemoglobins in different organisms relate to the environment and the way of life of the organism concerned?

 

Oxyhaemoglobin dissociation curve

Oxygen dissociation curves

• S-shaped curve – because shape of molecule is altered as each O2 molecule is taken up.

• After binding of first molecule shape changes so the binding of the others is easier.

• Steep part of the curve - small decrease in pp oxygen results in a big fall in Hb saturation, so that oxygen is released to the tissues where need is greatest.

PO2 (mmHg) % saturation of haemoglobin

10 13.5

20 35.0

30 57.0

40 75.0

50 83.5

60 89.0

70 92.7

80 94.5

90 96.5

100 97.5

Table 1. the percentage saturation of haemoglobin with oxygen at different partial pressures of oxygen

Plot a graph of PO2 against the percentage saturation of

haemoglobin. The curve obtained is called the oxygen haemoglobin dissociation curve.

Questions

The Bohr effect (shift)• CO2 reduces the

ability of Hb to combine with O2.

• CO2 present at respiring tissues – so Hb releases O2.

South American Llamas live at high altitudes. Where do you

think their oxygen dissociation curve would lie?

• Llamas – high altitude, little O2.

• Need higher affinity Hb – picks up O2 more readily, but releases it less readily.

• Curve also shifted to left for other organisms inhabiting low O2 environments – only releasing O2 when pp very low.

Higher affinity haemoglobins

1. Foetal haemoglobin – has higher affinity than maternal Hb, so can obtain O2.

2. Myoglobin – red pigment in mammalian muscles.

Has a higher affinity for O2 than Hb – only releasing it a very low pp.

Myoglobin ‘STORES’ O2.

Altitude sickness• Caused by acute exposure to low partial

pressure of oxygen at high altitude

• Compensated by altitude acclimatisation – body combats it by producing more red blood cells.

What animals would have a haemoglobin with a low affinity for oxygen and why? What would their

curve look like?

• Smaller animals (shrews/mice) and birds have curves shifted to the right.

• Have high metabolism so need O2 to be released readily.

0

20

40

60

80

100

0 4 8 12 16

Arterial PO2 (kPa)

Satu

ratio

n (%

)

Lesson Objectives(E) What are haemoglobins and what is their

role? (C) How do haemoglobins from different

organisms differ and why?(C) What is loading and unloading of oxygen? 

Lesson Objectives(E) What is an oxygen dissociation curve?(C) What is the effect of carbon dioxide on the curve and why?(A/B) How do the properties of the haemoglobins in different organisms relate to the environment and the way of life of the organism concerned?