S-Cool Revision Summary

S-Cool Revision Summary

Enzymes are biological catalysts. They speed up chemical reactions in all living things, and allow them to occur more easily. They occur in plant cells and animal cells. Without them we would not be alive.

Enzymes are just chemical molecules, made up of proteins.

Each particular enzyme has a unique, 3-dimensional shape shared by all its molecules. Within this shape there is an area called the active site where the chemical reactions occur.

Some enzymes help to break down large molecules.

Others build up large molecules from small ones.

While many others help turn one molecule into another.

Probably the fastest enzyme known is called catalase. It breaks the chemical hydrogen peroxide down to water and oxygen. Catalase is found in all cells and protects them from this dangerous waste chemical.

Each type of enzyme has its own specific optimum condition under which it works best.

Enzymes work best when they have a high enough substrate concentration for the reaction they catalyse. If too little substrate is available the rate of the reaction is slowed and cannot increase any further.

The pH must be correct for each enzyme. If the conditions are too alkaline or acidic then the activity of the enzyme is affected. This happens because the enzyme's shape, especially the active site, is changed. It is denatured, and cannot hold the substrate molecule.

Temperature is a key factor too. If it is too cold the enzymes will move around too slowly to meet the substrate molecules, so the reaction rate is slowed. Likewise, if it is too warm they do not work properly either. This is because the extra heat energy shakes them around so much that the active sites change shape so, just like with pH, the enzyme molecules are denatured, and can't hold the substrate.

Enzymes control all kinds of reactions in all cells. For example, they help control; respiration, photosynthesis, and our digestion, amongst many others.

Protease and lipase enzymes are used in biological washing powders to remove those stubborn stains.

Enzymes are also used in making foods and drinks. The enzyme pectinase helps to break down the cells in fruit to release more of their juice.