Red blood cells and Haemoglobin

What is blood made up of?

Blood is a tissue made up of cells (45%) in a solution of plasma (55%).

What is plasma?

Plasma is a pale yellow liquid, 90% water, containing solutes such as digested food molecules, urea, hormones and plasma proteins.

It also distributes heat.

Red blood cells are also called what?

Erythrocytes.

What shape do red blood cells have?

Biconcave disc.

How does the shape of the red blood cells allow them to carry out their function?

• This shape provides a large surface area to maximise diffusion of oxygen into the cells.

• The disc shape minimises the diffusion pathway for oxygen.

• The thinner central section allows the red blood cells the flexibility to squeeze through capillaries.

The colour of red blood cells is caused by what?

The respiratory pigment, haemoglobin.

Explain why red blood cells do not have a nucleus or any organelles.

There is more space to store haemoglobin molecules, which maximises the amount of oxygen which can be carried by each cell.

Explain why red blood cells lack mitochondria.

A lack of mitochondria means that oxygen is not used up in aerobic respiration while the oxygen is transported.

What is the function of haemoglobin?

Its main function is to transport oxygen from the lungs to the body tissues.

Describe the structure of haemoglobin.

Haemoglobin is a globular protein with a quaternary structure.

It consists of 4 polypeptide chains; There is also a prosthetic group containing an iron ion (Fe2+).

How many oxygen molecules can each haemoglobin molecule carry?

Each haemoglobin molecule can carry four oxygen molecules (eight atoms of oxygen).

What is formed when oxygen combines with a haemoglobin molecule?

Oxyhaemoglobin (HbO8​).

Hb + 4O₂ ⇌ Hb4O₂