Haemoglobin and Oxyhaemoglobin Dissociation Curves

What are the four components of blood?

Plasma, white blood cells, red blood cells, platelets

Which component of blood transports oxygen around the body?

Red blood cells

Which protein inside red blood cells helps them to transport oxygen?

Haemoglobin

What is the highest level of protein structure in haemoglobin?

Quaternary

Describe the structure of haemoglobin.

Four polypeptide chains, each bound to a haem group containing an iron ion

How many molecules of oxygen can an iron ion bind to?

One

How many molecules of oxygen can a single molecule of haemoglobin carry?

Four

What is the name of the structure formed when oxygen binds to haemoglobin?

Oxyhaemoglobin

What is positive cooperativity?

When the binding or unbinding of one particle makes it easier for another to bind or unbind

Explain what happens during positive cooperativity of oxygen molecules binding with haemoglobin.

When the first oxygen molecule binds, the quaternary structure of haemoglobin changes, exposing more of the other iron ions and making it easier for a second oxygen molecule to bind

What is the name of the process of oxygen binding to haemoglobin?

Oxygen association

What is the name of the process of oxygen unbinding from haemoglobin?

Oxygen dissociation

What process increases the speed at which oxygen association and dissociation takes place?

Positive cooperativity

Describe the partial pressure of oxygen in the lungs.

High

Describe the partial pressure of oxygen in the blood travelling to the lungs.

Low

Describe the partial pressure of oxygen in aerobically respiring cells.

Low

What is partial pressure measured in?

kPa or mm Hg

What is the relationship between partial pressure of oxygen and % saturation of haemoglobin with oxygen?

As partial pressure of oxygen increases, % saturation of haemoglobin with oxygen increases

What is % saturation of haemoglobin with oxygen a measure of?

The number of iron ions in the haemoglobin molecules which are bound to oxygen

What is the name of the graph of partial pressure of oxygen against % saturation of haemoglobin with oxygen?

Oxyhaemoglobin dissociation curve

What is the shape of the oxyhaemoglobin dissociation curve?

S-shaped

What is the reason for the steep gradient in the middle of the oxyhaemoglobin dissociation curve?

Positive cooperativity

Why does the oxyhaemoglobin dissociation curve plateau?

It becomes harder for oxygen molecules to find unbound iron ions to bind to

Which way does the oxyhaemoglobin dissociation curve shift when the concentration of carbon dioxide is low?

To the left

Which way does the oxyhaemoglobin dissociation curve shift when the concentration of carbon dioxide is high?

To the right

What is the Bohr effect?

When the oxyhaemoglobin dissociation curve moves to the left or right as a result of carbon dioxide concentration

What is the relationship between carbon dioxide concentration in the blood and pH of blood?

As carbon dioxide concentration increases, pH of blood decreases

Why does a higher carbon dioxide concentration in the blood result in a lower pH?

Carbon dioxide reacts with water in the blood to form H+ ions

What is the relationship between pH of blood and haemoglobin’s affinity for oxygen?

As blood pH increases, haemoglobin’s affinity for oxygen increases

What does haemoglobin having a high affinity for oxygen mean?

Oxygen associates with haemoglobin more readily and dissociates less readily

What does haemoglobin having a low affinity for oxygen mean?

Oxygen associates with haemoglobin less readily and dissociates more readily

If haemoglobin has a higher affinity for oxygen, which way will the oxyhaemoglobin curve shift?

To the left

If haemoglobin has a lower affinity for oxygen, which way will the oxyhaemoglobin curve shift?

To the right

What is the relationship between carbon dioxide concentration and haemoglobin’s affinity for oxygen?

As carbon dioxide concentration increases, haemoglobin’s affinity for oxygen decreases

Why may a species need a higher affinity for oxygen?

If they live in an environment with a low partial pressure of oxygen

Why may a species need a lower affinity for oxygen?

If they have a high metabolic/ respiration rate