B1.3

• Carbohydrates provide you with energy to move and stay alive
• Proteins are used for growth and repair of body tissues
• Vitamins and minerals help you to remain healthy
• Chemical reactions in your cells transfer energy from its chemical stores in food
• Metabolic rate is the amount of energy used by the body per unit of time
• The higher your metabolic rate, the more food you need to eat
• Some carbohydrates are polymers
• Carbohydrates are made from smaller molecules such as sugars
• Starch is an example of a carbohydrate polymer
• Starch is a chemical energy store
• In your body carbohydrase enzymes break down carbohydrates
• The enzyme that breaks down starch is amylase
• Proteins are polymers
• Proteins are formed from amino acids
• There are about 20 different amino acids
• In your body protease enzymes break down proteins into amino acids
• Lipids are the fats and oils that you eat
• Lipids are a good store of energy and some animals use them for insulation and buoyancy
• Lipids are synthesised from three fatty acids and glycerol
• In your body glycerol lipase enzymes break down lipids into fatty acids and glycerol
• Once food molecules are fully digested they are absorbed into your bloodstream and they travel to the cells that need them
• Energy is transferred so that you can move, grow and keep warm
• Your energy comes from chemical stores in the food you eat
• You get the oxygen needed for respiration from the air you breathe and blood then carries it to your cells
• Word equation for aerobic respiration:

  glucose + oxygen -> carbon dioxide + water
• Symbol equation for aerobic respiration

  C6H12O6 + 6O2 -> 6CO2 + 6H2O
• Aerobic respiration transfers energy from its chemical energy store in glucose to another chemical energy store for all processes in the cell (ATP)
• ATP (adenosine triphosphate) is used by all living organisms
• ATP produced in respiration is used:

  • to synthesise larger molecules from smaller ones to make new cell material
  • for movement
  • to stay warm
• Respiration takes place inside the mitochondria of a cell
• Each chemical reaction that takes place during respiration is controlled by a specific enzyme
• The number of mitochondria in a cell tells you how active the cell is
• During respiration energy is transferred to the surroundings by heating - it is an exothermic reaction
• During exercise your body will transfer energy from its chemical store in glucose by aerobic respiration
• Word equation for anaerobic respiration:

  glucose -> lactic acid
• Your body respires aerobically because:

  • aerobic respiration produces more ATP molecules per glucose molecule than anaerobic respiration produces
  • the lactic acid produced from anaerobic respiration can cause cramps (fatigue)
• You need to breathe more heavily after exercising because the oxygen you inhale reacts with the lactic acid, breaking it down - the oxygen needed for this is called the oxygen debt
• Anaerobic respiration in microorganisms and plants is known as fermentation
• Fermentation word equation:

  glucose -> ethanol + carbon dioxide
• Fermentation symbol equation:

  C6H12O6 -> 2C2H5OH + 2CO2