Enzymes
Catalysts in biological reactions are called A protein which catalyses or speeds up a chemical reaction..
Many of the chemical reactions inside the Basic unit of life. Unicellular organisms only have one cell. Multicellular organisms have many cells. of living things would be too slow without enzymes. These reactions occur in the breakdown of chemical molecules, which we see in the Organ system involved in breaking food down so that it can be absorbed into the bloodstream.. Enzymes are also involved in the building up of chemical molecules elsewhere in the body.
Enzymes are Organic compound made up of amino acid molecules. One of the three main food groups, proteins are needed by the body for cell growth and repair. that have a complex 3D shape. Each enzyme has a region called an The part of the enzyme to which a specific substrate can attach or fit on to..
The A substance on which enzymes act. - the molecule or molecules taking part in the chemical reaction - fits into the active site. Once bound to the active site, the chemical reaction takes place.
In an organism, the active site of each enzyme is a different shape. It is a perfect match to the shape of the substrate molecule, or molecules. This is essential to the enzyme being able to work. One enzyme is therefore specific to one substrate's chemical reaction, or type of chemical reaction.
This theory for the way in which enzymes work is called the Model which compares the specificity of enzymes with a key and its lock..
Factors affecting enzyme action
Physical factors affect enzyme activity.
Temperature
At low temperatures, the number of successful collisions between the enzyme and substrate is reduced because their The movement of molecules resulting from their kinetic energy. decreases. The reaction is slow.
The human body is maintained at 37°C as this is the temperature at which the enzymes in our body work best. This not true of the enzymes in all organisms.
How temperature affects enzyme action
Higher temperatures disrupt the shape of the active site, which will reduce its activity, or prevent it from working. The enzyme will have been To change the shape of an enzyme's active site, for example because of high temperatures or extremes of pH. Denatured enzymes no longer work..
Enzymes therefore work best at a particular temperature.
A graph to show the effect of temperature on enzyme activity:
The effect of pH
Enzymes are also sensitive to Scale of acidity or alkalinity. A pH (power of hydrogen) value below 7 is acidic, a pH value above 7 is alkaline.. Changing the pH of its surroundings will also change the shape of the active site of an enzyme.
Extremes of pH also denature enzymes. The changes are usually, though not always, permanent.
Enzymes work inside and outside cells. Cell pH is kept at 7.0 to 7.4 so cellular enzymes will work best within this pH range. Different parts of the digestive system have different pHs. The enzymes that catalyse reactions in each area have an The best or most appropriate - for instance, the conditions under which an enzyme works best (eg temperature and pH). pH that matches the pH of the area. For example, enzymes that work in the stomach have a very low optimum pH because of the acid present.
A graph to show the effect of pH on enzyme activity:
