Food and digestion

• What is a balanced diet


  a balanced diet  provides the correct amount of carbohydrates, protein, lipids, fibre, water, vitamins and minerals.
• balanced diet


  
• Eatwell guide


  
• What do we mean by biological molecules


  biological molecules are the molecules that all living organisms are made of.

  biological molecules are found in our food because we eat plants, fungi and other animals.
• Carbohydrates

  Simple Carbohydrates (sugars)

   

  Carbohydrates are made of the elements; C, H and O.

   

  Some carbohydrate molecules (e.g. glucose) are very small

   

  They are soluble - so they can dissolve - and they taste sweet

   

  We also call them sugars
• Carbohydrates

  Complex Carbohydrates (Starch and Glycogen)

   

  Lots of glucose molecules can be joined together to make complex carbohydrate molecules (e.g. starch and glycogen)

   

  These are very large

  They are insoluble and they tend to be found in foods that 'fill us up'.
• Food tests


  
• Testing for sugars:


  Use Benedict's solution

  If the food contains lots of sugar, the solution turns red

  If the food does not contain, the solution stays blue
• Testing for starch:


  Use Iodine solution

  If the food contains starch, the solution turns blue-black

  If the food does not contain starch, the solution stays orangey-brown
• Proteins:


  protein contains the elements C, H, O and N

   

  They are big molecules made of many smaller amino acid molecules
• Lipids


  Lipids (fats and oils) contain the elements C, H and O.

   

  They are big molecules made of one glycerol molecule and 3 fatty acid molecules

   
• Lipids


  
• Testing for protein:


  Use Biuret solution

  If the food contains protein, the solution turns purple

  If the food does not contain protein, the solution stays blue
• Testing for lipids (fats and oils)

  Use ethanol and water

  If the food contains lipids, the solution turns cloudy

  If the food does not contain lipids, the solution stays clear
• Calculate the amount of energy


  
• Energy requirements

  The amount of energy you need depends on:

  • Body size - the bigger you are, the more energy you use
  • How active you are - the more active you are, the more energy you use for muscle contraction
  • How fast you are growing - growth requires energy
• The digestive system


  
• How does food move through the digestive system

  When food is swallowed, it moves down the oesophagus (and through the rest of the digestive system) by peristalsis. This is the name for the waves of muscle contraction that push the food along. Muscles in front of the food relax (to make the tube wider) and muscles behind the food contract (to make the tube narrower). This squeezes the food forwards.

   
• Digestion


  
• Enzymes

  • Enzymes are proteins.
  • They act as catalysts.
  • This means that they are able to speed up reactions.
  • They are sometimes described as biological catalysts because enzymes speed up metabolic reactions in all living organisms (e.g. photosynthesis in plants).
• Enzymes

  • Each type of enzyme only speeds up one type of reaction.
  • This is because the substrate must be the right shape to fit into the active site of the enzyme.
  • We say that they are specific.

   

  How do enzymes work?

   

  1. Enzyme and substrate molecules in our cells move around slowly.
  2. When they collide, they bind to each other and a reaction occurs.
  3. The substrate changes into a product but the enzyme is unchanged.
  4. The enzyme can bind with more substrate.
• Enzymes


  
• Data Analysis: graph


  (5 marks):

  1. axis right way
  2. labelling axis
  3. scale + 1/2 paper
  4. plotting points
  5. line
• Data Analysis


  
• how does temperature affect enzyme activity

  before the optimum temp. (the highest point) the enzyme activity increases because the enzyme and substrate molecules are giving more kinetic energy, they move faster (more likely to collide)

  above the optimum temp. the rate of reaction decreases rapidly because the enzyme has denatured, meaning that the shape of an enzyme's active site changes at high temps. so the substrate can no longer bind
• how and why does pH affect enzyme activity

  enzymes work best at an optimum pH.

  at low or high pH values, the reaction slows down because the enzymes molecules denature

  
• Enzymes


  
• what happens in each part of the digestive system


  
• Bile


  what part of the digestive system makes bile: Liver

  where is bile stored: gall bladder

  
• Bile


  
• Bile


  
• Absorption


  
• CORMMSS

  
• CORMMSS experiment


  
• Water, vitamins & minerals


  
• Pancreas


  it produces lipase
• pH experiment

  At the optimum pH, the rate of reaction is fastest because the molecules are colliding frequently.

  Past the optimum, the enzymes are starting to denature. The active site is changing shape so the substrate no longer binds. The rate of reaction slows down.

   

   
• What is pH


  acidic or alkaline of a substance