The human digestive system

• What is the digestive system?

  An example of an organ system in which several organs work together to digest and absorb food
• What are the three main nutrients found in food?

  1. Carbohydrates
  2. Protein
  3. Lipids
• How is food transported around the body?

  1. Mouth
  2. Oesophagus
  3. Stomach- hydrochloric acid
  4. Small intestine
• What are enzymes?

  Biological catalysts. Proteins with a specific shape and active site that speed up chemical reactions
• What does denatured mean?

  When the shape of an enzyme active site is changed ans so it is unable to work
• How does the rate of activity of an enzyme change with pH levels?

  • As pH increased, the rate of enzyme activity increased until its optimum
  • Once past optimum, enzyme activity decreases, as the shape of the active site is changed
• How does the rate of activity of an enzyme change with temperature?

  • As pH increased, the rate of enzyme activity increased until its optimum as particles move faster so more frequent successful collisions
  • Once past optimum, enzyme activity decreases, as the shape of the active site is changed
• What is the role of digestive enzymes?

  Digestive enzymes convert food into small soluble molecules that can be absorbed into the bloodstream.
• What enzymes break down carbohydrates?

  Carbohydrases break down carbohydrates into simple sugars
• What is an example of a carbohydrase?

  Amylase- produced in the salivary glands, pancreas and small intestine
• What enzyme is used to break down proteins?

  Proteases break down proteins into amino acids
• What enzyme is used to break down lipids?

  Lipases breaks down lipids into glycerol and fatty acids
• Where is bile made?

  Liver
• Where is bile stored?

  Gall bladder
• What does bile do?

  1. it is alkaline to neutralise hydrochloric acid from the stomach
  2. Emulsifies fat to form small droplets which increase SA
• Which food test is used to test for sugars?

  Benedict's solution
• What food test is used to test for starch?

  Iodine
• Which food test is used to test for proteins?

  Biuret reagent
• What is a negative result for the presence of starch?

  Solution stays orange
• What is a positive result for the presence of starch?

  Blue - Black colour
• What is a negative result for the presence of sugars?

  blue
• What are the positive results of the presence of sugars?

  Green- small amount

  Yellow- more sugar

  Brick red- lots of sugar
• What is a negative result for the presence of proteins?

  Blue
• What is a positive result for the presence of proteins?

  Lilac
• How to test for lipids?

  Ethanol
• If a lipid is present the liquid will turn...

  white cloudy emulsion