Carbohydrates, Lipids and Proyeins
All carbohydrates are made up of units of sugar.Carbohydrates that contain only one sugar unit, eg glucose, or two sugar units, eg sucrose, are referred to as simple sugars.
Complex carbohydrates, eg starch and cellulose, are long chains of simple sugar units bonded together.
Lipids are molecules consisting of three molecules of fatty acids joined to a molecule of glycerol.
Protein molecules are made up of long chains of amino acids. These long chains are folded to produce a specific shape that enables other molecules to fit into the protein. Proteins act as:
- structural components of tissues such as muscles
Enzymes are biological catalysts. Catalysts increase the rate of chemical reactions. The shape of an enzyme is vital for the enzyme's function. High temperatures denature the enzyme, changing the shape of the active site. Different enzymes work best at different pH values.
Some enzymes work outside the body cells. The 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. Some microorganisms produce enzymes that pass out of the cells. These enzymes have many uses in the home and in industry.
In the home:
- biological detergents may contain protein-digesting and fat-digesting enzymes (proteases and lipases)
- biological detergents are more effective at low temperatures than other types of detergents.
- proteases are used to ‘pre-digest’ the protein in some baby foods
- carbohydrases are used to convert starch into sugar syrup
- isomerase is used to convert glucose syrup into fructose syrup, which is much sweeter than glucose and therefore can be used in smaller quantities in slimming foods.
Factors affecting enzyme action
Enzyme reactions are similar to other chemical reactions when the temperature is increased. Reactions take place faster when it is warmer. At higher temperatures, the molecules move around faster and so collide with each other more often with more energy.
However, if the temperature gets too hot, the enzyme stops working because the active site changes shape. We say that the enzyme becomes denatured. Each enzyme works best at a particular pH value. Some work best in acid conditions, such as the stomach, but others need neutral or alkaline conditions. If the pH is too acidic or alkaline for the enzyme, then the active site could change shape. Then the enzyme becomes denatured.
Some enzymes work outside the body cells:
- Digestive enzyes are produced by specialised cells in glands and in the lining of the gut.
- The enzymes pass out of the cells and come into contact with the food so it is digested.
- Digestion involves the breakdown of large, insoluble molecules into smaller molecules.
Making use of enzymes
Some microorganisms produce enzymes that pass out of their cells. These enzymes have many uses in industry but can be costly tp produce.
- Biological detergents contain proteases and lipases that digest food stains. They work at lower temperatures than ordinary washing powders. This saves energy and money spent on electricity.
- Protease are used to pre-digest proteins in some baby foods.
- Isomerase is used to convert glucose syrup into fructose syrup. Fructose is much sweeter, so less is needed in foods. The foods, therefore, are not so fattening.
- Carbohydrases are used to convert starch into sugar syrup for use in foods.
- In industry, enzymes are used to bring about reactions at normal temperatures and pressures. Traditional chemical processes require expensive equipment and a lot of energy to produce high temperatures and pressures.
Advantages of using enzymes:
- Enzymes in biological washing powders are very effective at removing stains such as blood, grass and gravy.
- Biological washing powders can be used at a lower temperature. This saves energy and reduces costs.
- Some enzymes are used in medicine to diagnose, control or even cure diseases.
Possible disadvantages of using enzymes:
- If people misuse washing powders they may have allergic reactiond on their skin. The enzymes are enclosed in capsules in the dry powder. Once the powder is dissolved, hands should not be placed in the water.
- Enzymes may enter waterways via the sewage system
- Industrial enzymes can be costly to produce
- Enzymes denature at the high temperatures needed to kill pathogens in the washing.
- Some fabrics such as wool will be digested by proteases