Biology topic 3: Organisation and the Digestive System.

1. 3.3: The Chemistry of Food

1.1. Carbohydrates are made up of units of sugar.

1.2. Simple sugars are carbohydrates that contain only one or two sugar units-they turn blue benedicts solution brick red upon heating.

1.3. Complex carbohydrates contain long chains of simple sugar units bonded together. Starch turns yellow/red iodine solution blue/black.

1.4. Lipids consist of 3 molecules of fatty acid bonded to a molecule of glycerol. The ethanol test indicates prescence of lipids in solutions.

1.5. Protein molecules are made up of long chains of amino acids. Biuret reagent turns from blue to purple in the presence of protein.

2. 3.4: Catalysts and Enzymes

2.1. Catalysts increase the rate of chemical reactions without chemically changing themselves.

2.2. Enzymes are biological catalysts and catalyse specific reactions in living organisms due to the shape of their active site. This is the lock and key theory of enzyme action.

2.3. Enzymes ate proteins. The amino acid chains are folded to make the active site, which matches the shape of a specific substrate molecule.

2.4. The substrate binds to the active site and the reaction is catalyzed by the enzyme.

2.5. Metabolism is the sum of all the reactions in a cell or the body.

3. 3.5: Factors Affecting Enzyme Action

3.1. Enzyme activity is affected by temperature and pH.

3.2. High temperatures denature the enzyme, changing the shape of the active site.

3.3. pH can affect the shape of the active site and make the enzyme work efficiently or stop it working.

4. 3.6: How the Digestive System Works

4.1. Digestion involves the breakdown of large insoluble molecules into soluble substances that can be absorbed into the blood across the wall of the small intestine.

4.2. Digestive enzymes are produced by specialized cells in glands and in the lining of the digestive system.

4.3. Carbohydrases such as amalyse catalyse the breakdown of carbohydrates into simple sugars.

4.4. Proteases catalyse the breakdowns of proteins into amino acids.

4.5. Lipases catalyse the breakdown of lipids to fatty acids and glycerol.

5. 3.1: Tissues and Organs

5.1. A tissue is a group of cells with similar function or  structure.

5.2. Organs are a collections of tissue performing specific functions.

5.3. Organs are organised into organ systems which work together to create organisms.

6. 3.2: The Human Digestive System

6.1. Organ systems are groups of organs that perform specific functions within the body.

6.2. The digestive system in a mammal is an organ system where several organs work together to absorb and digest food.

7. 3.7: Making Digestion Efficient

7.1. The protease enzymes of the stomach work best in acid conditions. The stomach produces hydrochloric acid, which maintains a low pH.

7.2. The enzymes made in the pancreas and the small intestine work best in alkaline conditions

7.3. Bile produced by the liver, stored in the gall bladder, and released through the bile duct neuteralises acid and emulsifies fats