enzymes and digestive system

• enzymes are catalysts produced by living things
• living things produce enzymes that act as biological catalysts
• a catalyst is a substance which increases the speef of a reaction, without being used up or changed in a reaction
• enzymes are all large proteins and all proteins are made up of chains of amino acids that are then folded into unique shape
• every enzyme has an active site with a unique shape that fits onto the substance involved in a reaction
• enzymes use the lock and key method to catalyse reactions
• enzymes work at a specifc pH range, if the pH is too high or too low, the enzyme's active site will change shape so the substance will no longer fit in. The enzyme will denature
• All enzymes have an optimum Ph that they work best at, it is often neutral ph7 but not always like pepsin used to break down proteins in the stomach which works best at ph2 meaning its weel-suited for acidic conditions
• Most enzymes catalyse only one reaction
• Carbohydrases (likes Amylase) convert carbohydrates into simple sugars 


  Amylase is made in the salivary glands, pancrease and small intestine
• Protease convert Proteins into Amino acids


  protease is made in the stomach (its called pepsin there), pancrease and small intestine
• Lipases convert lipids into glycerol and fatty acids


  Lipase is made in the pancrease and the small intestine
• lipids are fats and oils
• bile is made in the liver and is stored in the gall bladder before released into the small intestine
• bile neutalises the stomach acid and emulsifies fats
• the hyrdochloric acid in the stomach makes the Ph scale too acidic for enzymes in the small intestine to work properly, bile is alkaline (it neutralises the acid and makes conditions alkaline. the enzymes in the small intestine work best in alkaline conditions)
• bile breaks the fat into tiny droplets. this gives as much bigger surface area of fat for the enzyme lipase to work on- which makes the digestion faster
• rate of reaction 


  rate= = 1000/time
• salivary glands


  produce amylase enzyme in saliva
• oesophagus: the part of the alimentary canal which connects the throat to the stomach.
• stomach


  1.pummels the food with its muscular walls

  2.produces the protease enzyme, pepsin

  3.produces hrydochloric acid to kill bacteria and to give the right pH for the protease enzyme to work (pH 2-acidic)
• liver


  bile is produced that neutralises the stomach acid and emulsifies fats
• gall bladder


  bile is stored before its released into the small intestine
• pancrease


  produces protease, amylase and lipase enzymes that is released into small intestine
• large intestine


  where excess water is absorbed from the food
• small intestine


  produces protease, amylase and lipase enzymes to complete digestion

  also where digested food is absorbed out of the digestive system into the blood
• rectum


  where the faeces (made up mainly og indigestible food) are stored before they are transported to the anus...
• Major nutrients required for a healthy diet

  • Carbohydrates
  • Proteins
  • Lipids
• Digestive system


  Breaks down large molecules of food, which are then absorbed into the bloodstream
• The digestive system breaks down large molecules of food, which are then absorbed into the bloodstream
• Carbohydrates

  One of the major nutrients required for a healthy diet
• Proteins

  One of the major nutrients required for a healthy diet
• Lipids

  One of the major nutrients required for a healthy diet
• Digestive system


  1. Breaks down large molecules of food

  2. Absorbed into the bloodstream
• Qualitative tests


  Results that are not expressed as numbers or numerical data, eg they can be expressed as present or absent, or as colours
• Quantitative analysis


  Results that can be expressed using numerical values
• Benedict's test


  1. Heat in a water bath

  2. Detect presence of reducing sugars
• Reducing sugars


  • Glucose
  • Fructose
  • Lactose
  • Maltose
• Precipitate


  A suspension of particles in a liquid formed when a dissolved substance reacts to form an insoluble substance
• Iodine test


  1. Add iodine solution

  2. Detect presence of starch