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Breakdown of food in the digestive system Digestive enzymes • Digestive enzymes are produced by specialised cells in glands and in the lining of the gut. • The enzymes then pass out of the cells into the gut where they come into contact with food molecules. • They catalyse the breakdown of large molecules into smaller molecules. Starch molecules – large and branched Amylase – digestive enzyme Amylase breaks down starch into glucose and fructose Readily absorbed. Digesting carbohydrates • Enzymes which breakdown carbohydrates are called carbohydrases. • Amylase catalyses the breakdown of starch into glucose and fructose. • Amylase is produced in the salivary glands, pancreas and small intestine. Proteins – large and branched Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Breaks down proteins into amino acids. Amino acid Still too big! Amino acid Protease enzymes from the small intestine Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Amino acid Digesting proteins • The breakdown of protein is catalysed by protease enzymes. • Proteases are produced in the stomach, pancreas and small intestine. • Breakdown of proteins into amino acids takes place in the stomach and small intestine. Fats & Oils Fatty acids and glycerol which is easily absorbed. Bile from the liver mixes with the ‘fat’ to make an emulsion Lipase from the pancreas breaks down the fats to... Digesting lipids • Lipids are broken down into fatty acids and glycerol in your small intestine. • Reaction is catalysed by lipase enzymes. • Lipase enzymes are produced by the pancreas and the small intestine. Breakdown of food in the digestive system Objectives 1. Understand the uses of digested food. 2. Be able to explain digestion in the stomach. 3. Be able to explain the role of bile in digestion. Using the digested food • Glucose – Respiration • Fatty acids and glycerol – – – – Source of energy Build cell membranes Make hormones Fat stores • Amino acids – Protein synthesis What factors affect enzyme activity? substrate concentration surface area temperature pressure pH enzyme concentration Digestion in the stomach oesophagus mucus cells parietal cells (acid-producing) duodenum Enzymes in the stomach • The stomach produces hydrochloric acid. – It kills many harmful microorganisms that might have been swallowed along with the food. – The enzymes in the stomach work best in acidic conditions (pH2). Digestion in the small intestine Digestive enzymes found in the small intestine are damaged by a strongly acidic pH. How does the body avoid this problem? Digestion in the small intestine hepatic duct gall bladder pancreas duodenum bile duct Digestion in the small intestine • The liver produces bile (an alkali) – Stored in the gall bladder – Released into the small intestine. • Bile neutralizes the acidic contents coming from the stomach. • Provides alkaline environment for the enzymes in the small intestine. Altering the surface area • Bile emulsifies the fats in your food. – This means it physically breaks up large drops of fats into smaller droplets. – What effect will the increase in surface area have on the rate of fat digestion by lipase? Match each enzyme to its reactant Amylase Protein Lipase Starch Protease Carbohydrate Carbohydrase Fat Where are they broken down and what are they broken down into??? Starch Proteins Fats What are the two roles of bile?
