3.3.4.1: Haemoglobin and Oxygen Transport

What is the primary role of haemoglobin in red blood cells?

• To transport carbon dioxide

• To transport oxygen

• To provide energy to cells

• To fight infections

Answer explanation

The primary role of haemoglobin in red blood cells is to transport oxygen from the lungs to the tissues. While it can also carry some carbon dioxide, its main function is oxygen transport, making 'to transport oxygen' the correct choice.

What type of structure does haemoglobin have?

• Primary

• Secondary

• Tertiary

• Quaternary

Answer explanation

Haemoglobin has a quaternary structure, consisting of four polypeptide chains (two alpha and two beta) that form a functional protein. This structure is crucial for its ability to bind and transport oxygen effectively.

What is the effect of the first oxygen molecule binding to haemoglobin?

• It makes the binding of further oxygen molecules harder

• It has no effect on the binding of further oxygen molecules

• It makes the binding of further oxygen molecules easier

• It causes haemoglobin to release carbon dioxide

Answer explanation

The binding of the first oxygen molecule to haemoglobin induces a conformational change, making it easier for additional oxygen molecules to bind. This cooperative binding enhances oxygen uptake in the lungs.

What is the oxyhaemoglobin dissociation curve used to illustrate?

• The relationship between oxygen concentration and haemoglobin saturation

• The relationship between carbon dioxide concentration and haemoglobin saturation

• The relationship between pH and haemoglobin saturation

• The relationship between temperature and haemoglobin saturation

Answer explanation

The oxyhaemoglobin dissociation curve illustrates the relationship between oxygen concentration and haemoglobin saturation, showing how readily haemoglobin binds to oxygen at different oxygen levels.

What is the Bohr effect?

• The effect of temperature on haemoglobin's oxygen binding

• The effect of pH on haemoglobin's oxygen binding

• The effect of carbon dioxide concentration on the dissociation of oxyhaemoglobin

• The effect of oxygen concentration on haemoglobin's carbon dioxide binding

Answer explanation

The Bohr effect describes how increased carbon dioxide concentration lowers the pH, promoting the release of oxygen from hemoglobin. This enhances oxygen delivery to tissues that need it most, making the correct choice about carbon dioxide's role.

How does an increase in carbon dioxide concentration affect haemoglobin's affinity for oxygen?

• Increases affinity

• Decreases affinity

• Has no effect

• Causes haemoglobin to denature

Answer explanation

An increase in carbon dioxide concentration decreases haemoglobin's affinity for oxygen, a phenomenon known as the Bohr effect. This allows for more oxygen to be released in tissues where it is needed most.

What happens to haemoglobin when it releases oxygen?

• It binds to carbon dioxide

• It changes shape

• It becomes denatured

• It breaks down into amino acids

Answer explanation

When haemoglobin releases oxygen, it undergoes a conformational change, altering its shape. This change facilitates the binding of carbon dioxide, enhancing its ability to transport gases in the blood.

Which of the following best describes cooperative binding in haemoglobin?

• Each oxygen molecule binds independently

• Binding of one oxygen molecule decreases the affinity for others

• Binding of one oxygen molecule increases the affinity for others

• Oxygen binding is unaffected by other molecules

Answer explanation

Cooperative binding in hemoglobin means that when one oxygen molecule binds, it increases the affinity of the remaining binding sites for additional oxygen molecules, facilitating more efficient oxygen uptake.

What is the main component of red blood cells that carries oxygen?

• Plasma

• Platelets

• Haemoglobin

• White blood cells

Answer explanation

The main component of red blood cells that carries oxygen is haemoglobin. It binds to oxygen in the lungs and transports it to tissues throughout the body, making it essential for respiration.

What is the primary factor that causes haemoglobin to release oxygen in tissues?

• High oxygen concentration

• Low carbon dioxide concentration

• Low pH

• High pH

Answer explanation

Haemoglobin releases oxygen in tissues primarily due to low pH, which indicates higher carbon dioxide levels and increased acidity. This shift promotes oxygen unloading, enhancing oxygen delivery where it's needed most.