Digestion and nutrients

• Digestion


  The breakdown of large complex, insoluble food molecules into small, simple, soluble ones
• Digestive enzymes


  Chemicals that break down large molecules into smaller ones
• Digestive enzymes


  • Amylase, Protease, Lipase
• Molecules must be small to pass through the wall of the small intestines, into the blood and then to the cells
• Parts of the digestive system

  • Mouth
  • Liver
  • Gall bladder
  • Salivary Glands
  • Oesophagus
  • Stomach
  • Pancreas
  • Large intestine
  • Small intestine
  • Appendix
  • Rectum
  • Anus
• Functions of the mouth

  Teeth and tongue physically digest food, saliva chemically digests food
• Functions of the oesophagus


  Passage from mouth to stomach
• Functions of the stomach

  Digests proteins, contains hydrochloric acid
• Functions of the small intestine

  Digestion finishes here, nutrients are absorbed into blood
• Functions of the large intestine

  Water and salts absorbed here
• Functions of the rectum and anus

  Waste is stored before it leaves the body
• Hydrochloric acid is produced by the stomach to kill bacteria
• Carbohydrates begin to break down in the stomach
• The small intestine is where most of the water is absorbed
• Nutrients in food


  • Carbohydrates
  • Proteins
  • Fats
• Carbohydrates


  An energy store, e.g. starch in potatoes and glycogen in muscles of animals
• Proteins


  Used for growth and repair
• Fats


  An energy store, e.g. plants seeds or animal fat, butter
• Fats provide the most energy, followed by carbohydrates and then proteins
• If there are no carbohydrates or fats, proteins can be used for energy
• The energy content of different biscuits was investigated
• Independent variable


  Type of biscuits
• Controlled variables

  Same volume of water, same amount of biscuit from boiling tube, mass of biscuit
• Dependent variable


  Temperature change of water
• Safety precautions included safety goggles, heat proof mat, care with Bunsen burner, and letting ashes cool before disposal
• Method


  Measure 25cm of water into boiling tube, record initial temperature, take mass of biscuit, put biscuit on mounting needle, light Bunsen and move biscuit under boiling tube, when biscuit stops burning take final temperature of water, repeat for each biscuit
• If mass cannot be kept the same, energy released per gram of food must be calculated
• Biscuits with highest fat and carbohydrate content released the most energy
• Problems included incomplete burning of biscuits, heat loss to surroundings, and fat/crumbs falling off
• To improve the experiment, pure oxygen could be used for complete combustion, and a bomb calorimeter could be used
• The experiment was valid if it was repeated enough times, measured accurately, and was a fair test
• Careers that could use the results include nutritionist, dietician, and food scientist
• We need energy for growth, respiration, creating blood, movement, and digestion
• Cells need molecules like sugars to release energy in respiration
• Respiration


  The process where substances in cells react with oxygen to release energy
• Word equation for respiration

  Glucose + Oxygen → Carbon dioxide + Water + Energy
• Pregnant women and children require more energy due to growth needs
• Digested food enters the large intestine where water is absorbed from it.
• Proteins are broken down into amino acids during digestion.
• Carbohydrates are broken down into glucose during digestion.