1.6 Structure + function of blood compenents

Red blood cells (erythrocytes)

Function: Transport oxygen around the body

• Contain haemoglobin, which binds reversibly to oxygen.

• Biconcave disc shape - large sa:v

• No nucleus - more space for haemoglobin.

• Flexible, allowing them to squeeze through narrow capillaries.

• Thin centre - a short diffusion distance for oxygen.

White blood cells (leukocytes)

Function: Defend the body against pathogens

• Have a nucleus.

• Can change shape to move out of capillaries and into tissues.

• Two important types are phagocytes and lymphocytes.

• Phagocytes engulf pathogens; lymphocytes produce antibodies or differentiate into antibody-secreting plasma cells

Platelets

Function: Help blood clot.

• Small cell fragments without a nucleus.

• Become activated at damaged blood vessels.

• Help initiate a chain of reactions leading to fibrin formation.

• The fibrin forms a mesh that traps blood cells, helping form a clot.

Plasma

Function: Transports dissolved substances around the body.

• Straw-coloured liquid forming the main liquid component of blood.

• Mainly water.

• Transports glucose, amino acids, hormones, carbon dioxide, urea, antibodies, plasma proteins and heat.

• Carries blood cells and platelets around the circulatory system.

Nutrients in blood…

• glucose

• amino acid

• lipids

• vitamins

• mineral ions

• water

Haemoglobin & oxygen transport

• protein containing four haem groups, each with an iron ion that can bind one oxygen molecule.

  • In the lungs, where oxygen concentration is high, haemoglobin binds oxygen.

  • This forms oxyhaemoglobin.

  • In respiring tissues, where oxygen concentration is lower, oxyhaemoglobin releases oxygen.

  reversible reaction

Transport of CO2

• produced during respiration.

• A small amount dissolves in plasma.

• Some binds to haemoglobin.

• Most is transported as hydrogencarbonate ions, formed through reactions inside red blood cells.

It is transported to the lungs and exhaled.