Biology - Carbohydrates, Lipids, Proteins and Enzymes

Carbohydrates are made up of units of sugar and contain carbon, hydrogen and oxygen. Carbohydrates that contain one sugar unit are monosaccharides eg. glucose or two sugar units are disaccharides eg. sucrose. They are simple sugars.

Some carbohydrates contain many simple sugar units bonded together - these are called polysaccharides eg. starch. They are complex carbohydrates. 

Lipids are fats and oils consisting of 3 units of fatty acids joined to a molecule of glycerol.

Proteins are large molecules made from smaller units of amino acids. There are 20 naturally-occurring amino acids, but each molecule has hundreds/thousands of them joined together in a unique sequence and folded into a specific shape, giving each protein individual properties.

Proteins act as structural components of tissues (muscles), hormones, antibodies and enzymes.

An enzymes is a protein that acts as a biological catalyst - it speeds up biological reactions without being changed or used up. Enzymes are folded into complex shapes that allow smaller molecules (substrates) to fit into their active site. 

If the shape of an enzymes changes, its active site may no longer work - it has been denatured. This can happen due to high temperatures and extreme pHs. Some enzymes can work outside the body's cells.

Immobilised enzymes are enzymes that are attached to an inert, insoluble material (eg. calcium alginate). Immobilised enzymes can be used to make lactose intolerant/cat milk through catalysing the breakdown of lactose to glucose and galactose.

Advantages

• can catalyse the same reaction many times
• binding makes enzymes more stable and less likely to denature
• purification is not necessary

Disadvantages

• requires extra time, equipment and work
• may be reduction in reaction time
• cannot be used if one of the substrates is insoluble

Biological detergents (eg. washing powder) may contain protease and lipase to help break down stains such as blood and egg (protease) and oil and grease (lipase). Biological detergents are more effective at low temperatures than other types of detergents.

Proteases - break down proteins. They are used to 'pre-digest' solid food and break down milk proteins into amino acids in baby food. They are also used to break down allergenic proteins in hypoallergenic food.

Carbohydrases - break down carbohydrates. They are used to convert cheaper starch syrup into more valuable glucose syrup. Lactase, another carbohydrase is used to break down lactose into simple sugars for lactose intolerant people.

Isomerase - breaks down glucose. It is used to convert glucose syrup into fructose syrup. Fructose is much sweeter than glucose and can therefore be used in smaller quantities in slimming foods.