term one

• levels of organisation

  cells -> tissues -> organs -> organ systems -> organisms
• organs

  a group of tissues performing a specific function
• cells

  the basic building blocks of living things
• tissues

  a group of cells working together for the same function
• digestive system

  a group of organs that break down food and absorb the molecules
• organ systems

  a group of organs that carry out a specific function
• proteins:

  • functions are:
  • enzymes that act as catalysts
  • structural function eg hair
  • hormones
  • antibodies
  • made of chains of amino acids
  • bonds that hold these chains together are called peptin bonds
  • the test for protein is the biuret test
  • solution will turn purple
• carbohydrates:

  • made of carbon, hydrogen and oxygen only
  • there are two tests:
  • benedict's (for reducing sugars) which changes from blue to a brick red precipitate
  • iodine test (for starch) which changes from orange to blue - black
• carbohydrase is the enzyme that breaks down starch into glucose. eg amylase which is produced in the salivary glands and pancreatic amylase which is found in the pancreas.
• protease breaks down proteins into amino acids eg pepsin which is found in the stomach, pancreas and the small intestine wall.
• lipase breaks down lipids into glycerol and fatty acids. found in the pancreas and the small intestine.
• functions of arteries

  carry blood away from the heart - so is oxygenated.
• functions of veins

  carry blood to the heart - so is deoxygenated

  valves to prevent backflow
• the circulatory system has three main components: the heart, blood vessels and blood.
• capillaries have thin walls with no valves as they need to exchange substances easily between cells and blood.
• arteries carry blood away from the heart while veins carry blood towards it.
• red blood cells are responsible for carrying oxygen around the body.
• structure of arteries

  small lumen

  lining (endothelial tissue)

  muscle

  elastic fibres
• structure of veins

  thick lumen

  lining (endothelial tissue)

  muscle

  elastic fibres
• functions of capillaries

  gaps in the wall to allow gas exchange
• structure of capillaries

  small lumen

  endothelial tissue (one cell thick)
• the heart

  two sides

  four chambers

  right is deoxygenated

  left is oxygenated