B2 - Organisation

• The digestive system is an example of an organ system in which several organs work together to digest and absorb food.
• Enzymes catalyse specific reactions in living organisms due to the shape of their active site.
• Digestive enzymes convert food into small soluble molecules that can be absorbed into the bloodstream.
• Carbohydrases break down carbohydrates to simple sugars.

  Amylase is a carbohydrase which breaks down starch.

  Proteases break down proteins to amino acids.

  Lipases break down lipids (fats) to glycerol and fatty acids.
• The products of digestion are used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration.
• Bile is made in the liver and stored in the gall bladder. It is alkaline to neutralise hydrochloric acid from the stomach. It also emulsifies fat to form small droplets which increases the surface area
• In small intestine, The alkaline conditions and large surface area increase the rate of fat breakdown by lipase.
• The heart is an organ that pumps blood around the body in a double circulatory system. The right ventricle pumps blood to the lungs where gas exchange takes place. The left ventricle pumps blood around the rest of the body.
• The body contains three different types of blood vessel:

  • arteries

  • veins

  • capillaries.
• Blood is a tissue consisting of plasma, in which the red blood cells, white blood cells and platelets are suspended