Enzymes and their importance in plants and animals (25 marks)
Enzymes are biological catalysts, which accelerate the speed of chemical reactions in the body without being used up or changed in the process. Animals and plants contain enzymes which help break down fats, carbohydrates and proteins into smaller molecules the cells can use to get energy and carry out the processes that allow the plant or animal to survive. Without enzymes, most physiological processes would not take place. Hundreds of different types of enzymes are present in plant and animal cells and each is very specific in its function. Enzymes have an active site which has a complimentary base to a specific substrate, when these bind an enzyme-substrate complex is …show more content…

Consequently, animals and plant cells have some enzymes that are similar and some that are very different. In animals, enzymes are used in the formation of ATP. During the link reaction pyruvate is used to make acetate. Acetate is then picked up by co-enzyme A which forms acetyl co-enzyme A. This enzyme then enters the Krebs cycle. During the Krebs cycle coenzymes NAD and FAD remove the hydrogen and become reduced NADH and FADH. This is fundamental to the production of ATP in animals as it is the re-oxidation of NADH and FADH that produces ATP in the electron transport chain.
Animals also rely on enzymes for digestion, as without them, food could not be broken down and energy couldn’t be processed to a usable state. Some examples of enzymes secreted by animals include amylases, which digest starch, proteases, which digest protein, and lipases, which digest fat. In the digestive system, the necessary enzymes are secreted to prepare the food for absorption in the small intestine.
Enzymes are also involved in the regulation of blood glucose levels in an animal through a process called glycogenesis. When high levels are detected by the hypothalamus, beta cells respond by secreting insulin. Insulin fits with receptor proteins on liver and muscle cells. When inside the cells, insulin activates an enzyme that catalyses the condensation of glucose