Enzymes + digestive system

• A catalyst is a substance which increases the speed of a reaction without being changed or used up
• Enzymes are a protein so are made up of chains of amino acids
• The substance that an enzyme acts on is called the substrate
• Every enzyme has an active site which sits the substance involved in a reaction
• Enzymes generally only catalyse one specific reaction as the substrate has to fit into it's active site
• What is this theory called?

  Lock and key

  
• A higher temperature increases the rate of reaction until the enzyme is denatured (breaks down so shape of enzyme's active site is changed)
• PH effects enzymes, of it is too high or low bonds holding the enzyme together break, changing the shape of the active site and denaturing the enzyme
• Investigating pH & Enzyme Activity

  1. Add one drop of iodine to each of the wells of a spotting tile
  2. Place 2 cm3 of amylase into a test tube
  3. Add 1cm3 of buffer solution (at pH 2) to the test tube
  4. Add 2 cm3 of starch solution to the test tube, mix + start stopwatch
  5. Every 30 seconds, transfer a droplet of the solution to a new well on spotting tile until the iodine solution stops turning blue-black and remains brown (meaning amylase has broken down all the starch)
  6. Record time and repeat experiment with buffers at different pH values
• Rate of reaction = 1000 / time
• Starch, proteins and fats are too big to pass through the walls of the digestive system so digestive enzymes break down these big molecules into smaller ones like sugars (glucose and maltose), amino acids, glycerol and fatty acids. These smaller molecules can be absorbed into the bloodstream.
• Starch is a carbohydrate
• Amylase is made in the

  • Salivary glands
  • Pancreas
  • Small intestine
• Amylase breaks down starch into maltose
• Protease breaks proteins down into amino acids
• Proteases are made in

  • Stomach
  • Pancreas
  • Small intestine
• Amylase is a carbohydrase
• Lipases convert lipids into glycerol and fatty acids
• Lipids are fats and oils
• Lipases are made in

  • Pancreas
  • Small intestine
• Bile neutralises stomach acid and emulsifies fats
• Bile is produced in the liver and stored in the gall bladder before being released into the small intestine
• Bile emulsifies fats (breaks it down) which gives a much larger surface area for enzyme lipase to work on
• Label image

  A) Salivary glands

  B) Gullet

  C) Liver

  D) Stomach

  E) Pancreas

  F) Small intestine

  G) Rectum

  H) Large intestine

  I) Gallbladder

  
• Fill in the gaps

  A) pepsin

  B) hydrochloric acid

  
• Salivary glands produce amylase enzyme in saliva

  
• Bile is produced in the liver
• Gall bladder stores bile
• Pancreas produces protease, amylase and lipase enzymes
• Small intestine produces protease, amylase and lipase enzymes and is where digested food is absorbed by the blood
• Large intestine is where excess water is absorbed from food
• Rectum is where faeces is stored