biology - organisation

• specialised cells form tissues, which form organs, which form organ systems
• A tissue 


  a group of similar cells that work together to carry out a specific function.
• An organ


  A group of different tissues that work together to perform a certain function.
• An organ system


  A group of organs working together to perform a particular function.
• What does the digestive system do?

  Breaks down and absorbs food.
• Where are the 5 stages of digestion?

  1. Gland
  2. The stomach & small intestine
  3. The liver
  4. The small intestine
  5. The large intestine
• Enzymes


  Catalysts produced by living things that speed up the rate of a reaction without being changed or used up in the reaction.
• Enzymes are all large proteins that are made up of chains of amino acids.
• Every enzyme has an active site with a unique shape that fits onto the substance involved in a reaction.
• Changing the temperature changes the rate of an enzyme-catalysed reaction. If it gets too hot, some of the bonds holding the enzyme together break and the enzyme becomes denatured.
• All enzymes have an optimum temperature which they work best at.
• How does pH affect enzymes?

  If its too high/low, the pH inteferes with the bonds holding the enzyme together. This changes the shape of the enzyme and denatures the enzyme.
• Amylase is an example of carbohydrase. It breaks down starch.
• Starch is broken down by the amylase enzyme in to simple sugars
• Amylase is made in the 3 places:


  1)the salivary glands

  2)the pancreas

  3)the small intestine
• proteases convert proteins into amino acids
• proteins are broken down by the protease enzyme into amino acids
• Proteases are made in 3 places:

  1. the stomach
  2. the pancreas
  3. the small intestine
• Lipases convert lipids into glycerol and fatty acids
• Lipids are broken down by lipase enzymes into glycerol and fatty acids
• Lipases are made in 2 places:

  1. the pancreas
  2. the small intestine
• Bile neutralises the stomach acid and emulsifies fats.

  Bile is produced in the liber and stored in the gall bladder before its released in to the small intestine.
• salivary glands


  these produce amylase enzymes in the saliva
• liver


  where bile is produced
• gall bladder


  where bile is stored before its released in to the small intestine
• large intestine 


  where excess water is absorbed from the food
• rectum


  where the faeces are stored before leaving through the anus
• stomach


  1 . pummels the food with its muscular walls

  2. produces the protease enzyme, pepsin

  3. produces hydrochloric acid to kill bacteria & to give the protease enzyme the right pH
• pancreas


  produces protease, amylase and lipase enzymes. It releases these into the small intestine.
• small intestine


  produces protease, amylase and lipase enzymes to complete digestion.

  Also where the digested food is absorbed out of the digestive system into the blood.
• Lungs supply oxygen in to the bloodstream to supply your cells for respiration.
• The alveoli carry out gas exchange in the body.
• The lungs contain millions of little air sacs called alveoli surrounded by a network of blood capillaries. This is where gas exchange happens.
• The heart contracts to pump blood around the body
• The walls of the heart are mostly made of muscle tissue.
• The heart has valves to make sure the blood flows in the right direction- prevent backflow.
• blood flows into the 2 atria from the vena cava and pulmonary vein
• the atria contract, pushing blood into the ventricles
• the ventricles contract, forcing the blood into the pulmonary artery and the aorta, and out of the heart.
• the blood then flows to the organs through arteries, and returns through veins.