Digestion

• Digestion is a process whereby large food molecules are broken down into smaller molecules.
• There are 2 types of Digestion: Mechanical/ Physical Digestion and Chemical Digestion
• Mechanical digestion is a process whereby food is broken down into subunits voluntarily (with the use of human effort).
• Mechanical Digestion occurs in the mouth by teeth.
• 2 Structures within the body that breakdown food mechanically are: the mouth (carried out by teeth due to mastication) and the stomach ( done by churning/ the contraction and relaxation of the stomach walls.
• Chemical digestion is a process whereby enzymes are used to break down/ convert large molecules into smaller pieces (micro-molecules/ sub units).
• An enzyme is a biological catalyst that speeds up the rate of a chemical reaction.
• The function of an enzyme is to lower the activation energy required for a reaction to occur which is used to convert reactions into products.
• Enzymes are made from globular protein.
• There are 2 types of protein: fibrous strands and globular protein.
• All enzymes are protein but not all proteins are enzymes.
• pH means Power of Hydrogen
• Enzymes work at a particular pH (mostly neutral 7)
• Enzymes are required in small amounts. They are highly specific and are denatured/ destroyed at high temperatures or pH.
• For an enzyme to breakdown a substrate (macro-molecule) the following can occur: the substrate is compatible with the active site of the enzyme.
• The active site of an enzyme is where a substrate will bind so that the enzyme can increase the rate of reaction and produce product
• the mouth chews food and mixes it with saliva.
• the salivary gland produces saliva
• the tongue rolls food into bolus to travel down the esophagus via peristalsis
• the epiglottis closes over the trachea during swallowing.
• the esophagus transports food to the stomach.
• the liver produces bile.
• the gall bladder stores bile.
• the stomach produces gastric juices./ where digestion of protein begins.
• the pyloric sphincter is a muscle which relaxes periodically to release food from the stomach.
• the pancreas produces pancreatic juice.
• (duodenum & ileum)- the small intestine 1. produces intestinal juice. 2. receives bile and pancreatic juice
• Digestion of starch, maltose, sucrose, lactose, lipids, proteins and peptides is completed.
• the colon absorbs water
• the rectum stores faeces and waste products from the small intestine for egestion
• the anal sphincter muscle relaxes during egestion.
• the anus expels faeces.
• the liver: - produces bile - regulates blood sugar levels - stores vitamins and minerals - produces blood proteins - produces cholesterol - produces heat - regenerates liver cells - metabolises nutrients - synthesises hormones - remove old blood cells - filters and excreates bilirubin.
• The enzyme amylase, found in the mouth, breaks down starch into maltose.
• The enzyme pepsin, found in the stomach, breaks down protein in smaller peptides.
• The enzyme trypsin, found in the small intestine, breals down fat into fatty acids and glycerol
• The enzyme lactase, found in the small intestine, breaks down lactose into dairy.
• The enzyme sucrase, found in the small intestine, breaks down sucrose into glucose and fructose.
• The enzyme maltase, found in the small intestine, breaks down maltose into glucose.
• The enzyme chymotrypsin, found in the small instestine, breaks down proteins into smaller peptides (amino acids)