Organisation: The Cardiovascular & Respiratory System (AQA GCSE Biology): Revision Notes

2.2.3 Blood Vessels & Blood

1. Plasma

• This is liquid that carries the components in the blood: red blood cells, white blood cells, platelets, glucose, amino acids, carbon dioxide, urea, hormones, proteins, antibodies and antitoxins

2. Red blood cells

• They carry oxygen molecules from the lungs to all the cells in the body

• Their bioconcave disc shape provides a large surface area

• They have no nucleus allowing more room to carry oxygen

• They contain the red pigment haemoglobin, which binds to oxygen and forms oxyhaemoglobin

  

3. White blood cells

• They are a part of the immune system, which is the body's defence against pathogens (microorganisms that can produce disease)
• They have a nucleus
• There are a number of types:

1. Those that produce antibodies (small proteins that clump them together) against microorganisms
2. Those that engulf and digest pathogens
3. Those that produce antitoxins to neutralise toxins (poisons) produced by microorganisms

4. Platelets

• They help the blood clot form at the site of a wound
• The clot dries and hardens to form a scab, which allows new skin to grow underneath while preventing microorganisms from entering
• Small fragments of cells
• No nucleus
• Without them, cuts would result in excessive bleeding and bruising