Mass Transport in Mammals

haemoglobin, dissociation curves, blood vessels, the heart and cardiac cycle, tissue fluid

What type of protein is haemoglobin?

Quaternary protein

How many polypeptide chains are there in haemoglobin?

4 - 2 alpha, 2 beta

Each polypeptide chain in haemoglobin contains what?

A haem group

What ion can be found in a haem group?

An iron (ferrous) ion - Fe²⁺

What do iron ions in haemoglobin bind to?

Oxygen molecules

What is it called when oxygen binds to haemoglobin?

Oxyhaemoglobin

How many oxygen molecules can haemoglobin carry?

Up to 4

What is partial pressure?

The measure of how much something is present

What is the abbreviated of the partial pressure of oxygen?

pO₂

What is the general formula for partial pressure?

p[substance]

What is partial pressure measured in?

kPa (kiloPascals)

What is the pO₂ in different parts of the body?

Lungs: high pO₂

Respiring tissue: low pO₂

What is affinity?

How much a substance will combine with another (in this case, how much haemoglobin combines with oxygen)

What is oxygen affinity like in different parts of the body?

Lungs: high affinity

Respiring tissue: low affinity

What happens to haemoglobin at the lungs and why?

Haemoglobin loads with oxygen

Because pO₂ is high, so affinity is high

What happens to haemoglobin at respiring tissue and why?

Haemoglobin unloads

Because pO₂ is low, so affinity is low

What does an oxygen dissociation curve show?

What haemoglobin affinity is at different partial pressures

What are on the axes of an oxygen disocciation curve?

Percentage saturation of haemoglobin
pO₂

What type of shape do dissociation curves tend to have? What is this called?

S shape

Sigmoidal curve

What is haemoglobin saturation like at the a) lungs b) respiring tissue

a) high

b) low

What is the pO₂ in the lungs?

12kPa

What is the gradient of a dissociation curve like at high pO₂? What does this show?

Flat
Even if there is a small reduction in pO₂, the haemoglobin will still remain highly saturated

What does the steepest part of a dissociation curve correspond with? What does this show?

The pO₂ of tissues

Shows how efficient haemoglobin is at unloading O₂ because a small decrease in pO₂ causes a large fall in saturation

The regular dissociation curve for humans acts under what conditions?

Low pCO₂

What is the effect of CO₂ on a dissociation curve called?

The Bohr effect

What is the Bohr effect?

The effect of CO₂ on a dissociation curve

Which way does the Bohr shift shift the dissociation curve?

To the right

What does a shift to the right of a dissociation curve mean?

Haemoglobin has a lower affinity for oxygen and unloads at higher pO₂s

When is the Bohr effect useful?

In respiring tissue

Why does more CO₂ affect haemoglobin saturation?

It changes the pH

How is the Bohr effect useful in respiring tissue?

CO₂ will be being produced from aerobic respiration

So the curve shifts right

This allows haemoglobin to give more oxygen to the respiring tissues (even when pO₂ is still high)

This allows the tissues to continue respiring