oxygen dissociation and bohr effect lesson 1 of 2

Why train at high altitudes?

Who will feel weaker at high altitudes?Why?

Andy Murray? A Tibetan Sherpa?

Module 2: Exchange and transport

Carriage of oxygen

We are learning to…

Describe the role of haemoglobin in carrying oxygenExplain the significance of different affinities for oxygen of fetal

and adult haemoglobin

You will be able to…

Describe and explain a dissociation curveCompare the affinity of different respiratory pigments

Transport of Oxygen…

PARTIAL PRESSURE OF OXYGEN (pO2)

What is it?

Dissociation curve

Key words

•Dissociation

•Affinity

•Partial pressure

•Saturation

Key terms

• The partial pressure is the pressure one gas in a mixture would exert if it were the only gas present in the volume under discussion

• Dissociation is a general process in which compounds separate or split into smaller particles, ions, or radicals, usually in a reversible manner.

• Saturation – refers to the fraction of total protein binding sites that are occupied at any given time

Oxygen transport• Haemoglobin is made up of four subunits (2

alpha, 2 beta haem groups) and an iron atom. There are many specialised respiratory pigments that are able to reversibly bind to a respiratory gas.

• 4Hb + 4O2 ↔ Hb4O8

• When an oxygen molecule binds to one subunit , it increases the affinity of the other subunits. This relationship is reflected in the dissociation curve. Myoglobin is a pigment that stores oxygen in the muscles.

• The dissociation curve is SIGMOIDAL

Adaptation to hypoxic environments

• At high altitudes, the air is thinner and therefore the partial pressure of oxygen is comparatively lower than closer to sea level.

• Aquatic environments also class as hypoxic.

• To overcome these problems, organisms have evolved large stores of myoglobin, and Hb with a higher affinity for oxygen at lower PO2

Fetal Haemoglobin

Bohr effect• Increased carbon dioxide levels lowers the pH of

the blood• This affects the ability of the haemoglobin

subunits to transport oxygen• A lower pH causes theHaemoglobin to releasemore oxygen• A higher pH causes the Haemoglobin to hold ontomore oxygen

Endurance training• Exposure to hypoxic conditions can affect the

Hb and stimulate a greater release of red blood cells, thus increasing the oxygen carrying potential of the blood.

• Increased concentration of erythropoietin • 2, 3-DPG is an organic compound in

erythrocytes that binds with deoxy-haemoglobin

• Reduces affinity of Hb for oxygen to enable unloading in capillaries (shifts curve to RIGHT)