Enzymes and Human Nutrition: notes

Enzymes

• Enzyme: a protein that speeds up a reaction without being used up.
• Temperature: rate rises to an optimum, then the enzyme is denatured and stops working.
• pH: each enzyme has an optimum pH; pepsin works in acid, amylase near neutral.

Diet and digestion

• Balanced diet: carbohydrates, proteins, fats, vitamins, minerals, fibre and water.
• Food tests: iodine for starch, Benedict's for reducing sugar, biuret for protein, ethanol for fat.
• Deficiency: lack of vitamin C causes scurvy; lack of iron causes anaemia; lack of protein causes kwashiorkor.
• Digestion: amylase breaks starch to sugar, protease breaks protein to amino acids, lipase breaks fat to fatty acids and glycerol.
• Absorption: happens in the small intestine through villi; water is absorbed in the large intestine.
• Teeth: incisors cut, canines tear, molars grind. Sugar and bacteria cause decay.