The Blood (WJEC GCSE Biology)

Components of Blood

• Blood consists of red blood cells, white blood cells, platelets and plasma

  • Over half of the volume of the blood is made up of plasma

  • Around 45 % is made up of red blood cells

  • The remaining fraction consists of white blood cells and platelets

Blood micrograph diagram

Red blood cells, white blood cells and platelets can be observed when blood is viewed under a microscope

Blood parts functions table

Drawing Blood Cells

• In an exam you may be asked to draw two types of blood cells: red blood cells and phagocytes (which are a type of white blood cell)

Labelled drawing of a red blood cell diagram

A drawing of a red blood cell in an exam would only need to be very basic, as shown in the image here

• When drawing a red blood cell remember the following points:

  • A red blood cell has a circular structure and is sometimes drawn with a secondary inner circle to represent the biconcave shape

  • It has no nucleus

  • You need to be able to label the cell membrane

Labelled drawing of a phagocyte diagram

A drawing of a phagocyte in an exam would only need to be very basic, as shown in the image here

• When drawing a phagocyte remember the following points:

  • It does not have a fixed shape because it can flex its shape to engulf pathogens

  • It has a three-lobed nucleus (three circles joined by thin stems)

  • You need to be able to label the cell membrane, the nucleus and the cytoplasm