(human nutrition)

• Food groups:

  • fibre
  • water
  • carbohydrate
  • protein
  • fats
  • minerals
  • vitamins
• biological molecules are macromolecules built from simple molecules which join together through condensation reactions
• Food test:

  • glucose = benedict solution (blue - yellow - black)
  • starch = iodine solution (brown - orange - black)
  • protein = biuret solution (blue - purple)
  • lipid = ethanol + water (colourless - milky white)
• carbohydrates (e.g. bread) are a respiratory substance oxidised to release energy in active transport
• proteins (e.g. milk) are a building block for growth and repair in body tissues
• water is a transport medium, substrate in digestive reactions
• fats (e.g. fish) help the body absorb vitamins
• calcium (e.g. milk) is for healthy bones and teeth
• Iron (e.g. red meat) is for haemoglobin in red blood cells
• vitamin D (e.g. milk) is for absorbtion of calcium
• vitamin A (e.g. carrors) is responsible for pigment formation in retina for vision
• the amount of energy used should equal to the energy intaked from food
• esophagus pushes food down to stomach through peristalsis
• stomach churns and stores food, protein and water is digested, gastric protease is produced
• liver produces bile to gall bladder
• gall bladder concentrates bile to digest fat in small intestine
• small intestine digests and absorbs food, maltase and protease is produced
• large intestine absorbs water from food
• rectum compacts undigested food into faeces
• salivary glands produce saliva to lubricate food for swallowing
• peristalsis is a series of muscle contractions
• emulsification is the process of breaking down large lipids into smaller several lipids. The liver releases bile, and it grabs onto fats, increasing their surface area with emulsifiers
• enzymes (proteins) is a biological catalyst that increases the rate of reaction in living organism, it controls metabolism
• enzymes are sensitive to pH and temperature, the further away they are from the optimum, the more the enzyme denatures, its active site changes shape and can no longer react with substrates
• chewing mixes saliva with our food, which contains amylase that starts the process of breaking down starch into glucose
• the lining of the stomach produces gastric juice (HCl + pepsin) that kills any bacteria and provide optimum pH to break down protein into amino acids
• liver produces bile to neutralise acid from stomach to provide optimum pH and to form emulsion
• the inner lining of the small intestine is covered with villi which enhance the surface area for absorbtion
• all metabolic work generates heat for endotherms to use as food energy
• ways villi are adapted for absorption:

  • lacteal (transport fat-soluable to lymph)
  • dense network of capillaries (water-soluable to blood)
  • microvilli (increase surface area)
  • thin wall (decrease diffusion distance)
• enzymes and uses:

  • carbohydrase = carbohydrates -> glucose
  • amylase = starch -> glucose
  • protease = protein -> amino acids
  • liplase = fats -> glycerol, fatty acids
• collision theory is that when thermal energy increases, particles move faster, so there are more collisions in a given amount of time. therefore reactions catalase more