Organisation

• Label the image

  A) mouth

  B) oesophagus

  C) liver

  D) stomach

  E) small intestine

  F) large intestine

  G) rectum

  H) anus

  I) pancreas

  J) gallbladder

  
• Digestion is the process of large, insoluble food particles being broken down into smaller soluble particles
• Mechanical digestion involves physical breakdown of food by chewing or grinding.
• Chemical digestion involves enzyme-controlled reactions that break down large food particles into smaller ones
• What are the functions of the organs in the digestive system? (1)

  • Mouth - Contains teeth (chews down food into smaller pieces) and the tongue (pushes the food down into the oesophagus)
  • Salivary glands - Produces amylase in the saliva
  • Oesophagus - Transports food from the mouth to the stomach by squeezing it down
  • Stomach - Produces hydrochloric acid (which kills bacteria and provides the right PH for enzymes) and contains pepsin (which helps to break down food into smaller pieces)
  • Liver - Produces bile
• What are the functions of the organs in the digestive system? (2)

  • Pancreas - Produces amylase, (both) proteases and lipase
  • Gall bladder - Stores bile before it released into the small intestine
  • Small intestine - Adsorbs nutrients (contains amylase, trypsin and lipase which break down food so nutrients can enter the bloodstream)
  • Large intestine - Adsorbs water from food
  • Rectum - Stores feces
  • Anus - Releases feces
• Bile nuetralises stomach acid and emulsifies fat
• Enzymes are biological catalysts made from chains of amino acids that break down foods into smaller molecules that can pass through the digestive system easily and are adsorbed into the bloodstream
• Catalysts are substances that speeds up a chemical reaction without being used up
• Three enzymes are amylase, protease and lipase
• Amylase is a carbohydrase
• Two proteases are pepsin and trypsin.
• What are the functions of these enzymes?


  • Amylase: breaks carbohydrates (starch) down into glucose
  • Protease: breaks down proteins into amino acids
  • Lipase: breaks down fats into glycerol & fatty acids
• Where are these enzymes produced?


  • Amylase: salivary glands, pancreas, small intestine
  • Protease: stomach (pepsin), small intestine (trypsin), pancreas (both)
  • Lipase: small intestine, pancreas
• A substrate is a substance that is used by an enzyme to catalyse a reaction (the reactant)
• Every enzyme has an active site that is a specific shape that fits a specific substrate
• A substrate fits into the active site of an enzyme like a lock fits into a key
• During the reaction, the enzyme breaks the substrate into two products
• Label the image

  A) substrate

  B) enzyme

  C) active site

  D) enzyme substrate complex

  E) products

  F) enzyme is unchanged after the reaction

  
• The enzyme-substrate complex is formed when the substrate binds with the active site on the enzyme.
• When an enzyme becomes denatured it means the shape of the active site has changed. Therefore the enzyme won't fit into the substrate and it no longer works
• Every enzyme works best at a specific temperature and pH. This is called the optimum (temperature/pH)
• If an enzyme is outside of the optimum range, it may become denatured
• A suitable enzyme speeds up the reaction as it lowers the activation energy
• What are the optimum pH values of the following enzymes?


  • Salivary amylase - 6-7
  • Stomach protease - 1-2
  • Pancreatic lipase - 8
• • Stomach acid lowers the pH
  • Bile raises the pH
• Changing the temperature changes the rate of the enzyme reaction. A higher temperature increases the rate at first but if it gets too hot the enzyme denatures
• What are the different food groups?

  • Carbohydrates (eg. breads, cereals, sugary foods)
  • Proteins (eg. meats, eggs, dairy)
  • Fats (eg. fatty foods, oil, butter)
  • Fibre (e.g fruits, vegetables, cereals)
  • Vitamins (eg. fruits, vegetables)
  • Minerals (eg. dairy)
  • Water (eg. drinks)
• What are the functions of the different food groups?

  • Carbohydrates - energy
  • Proteins - growth and repair
  • Fats - keep us warm & energy
  • Fibre - add bulk to food (prevents constipation)
  • Vitamins - keep us healthy
  • Minerals - strong bones & teeth
  • Water - hydration
• Metabolism is the sum of all the reactions in a cell or organism (the reactions in which molecules are made or broken down)
• The factors that effect metabolism are:

  • Age
  • Exercise
  • Family history
  • Gender
• If the pH is too high or low it interferes with the bonds holding the enzyme together. This changes the shape of the active site and the enzyme becomes denatured
• All enzymes have an optimum pH range where they are most active. This is often 7 (neutral) but it varies
• To perform a food test, you will need a food sample. To prepare a food sample you will need to:

  • Take a piece of food and break it down using a pestle and mortar
  • Transfer the broken down food to a beaker and add some distilled water
  • Stir the mixture with a glass rod to dissolve some of the food
  • Filter the mixture with a funnel lined with filter paper to get rid of the solid bits
• To test for sugars we use Benedict's solution. If sugar is present, the solution will change from blue to (green, yellow or) brick red (depending on how much sugar is in the food)
• To test for starch we use iodine solution. If starch is present, the solution turns from a orangey-brown colour to a blue-black colour.
• To test for proteins we use biuret solution. If protein is present it will change the colour of the solution from blue to lilac.
• To test for lipids we can use the Sudan III stain solution. If lipids are present, the solution will separate into two layers. The top layer will be bright red.
• The scientific name for fats are lipids.
• To test for lipids we can also use Ethanol. If lipids are present, the solution will change from being clear to cloudy