Enzymes and their functions

What are enzymes

Enzymes are proteins in body cells that act as biological catalysts to speed up the chemical reactions in living cells. A catalyst is any product that increases the rate of chemical reactions without it being altered. An enzyme can catalyze a given chemical reaction over and over again. Enzymes can make a reaction a million times faster than it would have without enzymes. Enzymes are made of chains of interconnected amino acids. Each enzyme has got a unique sequence of amino acids hence the unique shapes. The sequence of these amino acids depends on the gene of the cell nucleus.

Enzymes can also be imprisoned to restrict their movements in the cell in a process called enzyme immobilization. Immobilized enzymes are stable and do not mix with substrates. This makes the separation of enzymes and product easier, allows for reuse of enzymes and prevents enzyme contamination of the product.

Enzymes are present all over the body. In the digestive system, they catalyze the breakdown of the large complex food molecules into smaller molecules that can be used to fuel the body. In the liver, they catalyze the breakdown of toxins. Examples of specific enzymes in the human body are Lipase that help digest fats in the gut, Trypsin in small intestines that help breakdown proteins to amino acids, Amylase, Lactase, Helicase, Maltase, and DNA Polymerase.

Enzymes have a special cleft known as the active site on their surface. Reagents meet and interact in the active site of the enzyme. An enzyme has an induced-fit model that only accommodates certain reagents. A given enzyme can only catalyze a specific chemical reaction. When the reagents enter the active site of the enzyme they temporarily change their shape to be able to react with the other reagents.

Enzymes work hand in hand with coenzymes/cofactors. The role of cofactors is to activate the enzymes. Cofactors are metal ions like copper, zinc, magnesium, and iron. Magnesium is the common cofactor, it is said to activate hundreds of chemical reactions in the body. Among the enzymes activated by magnesium is those that catalyze the metabolism of carbohydrates and those that help in manufacture DNA. Vitamins are the main source of cofactors. Vitamin C provides cofactors needed by enzymes that are responsible for the production of collagen and building healthy skin, Vitamin B6 is needed by coenzymes responsible for the production of serotonin, Vitamin B12 is needed by coenzymes that synthesis insulin around the nerve endings.

The performance of enzymes is affected by body conditions such as body temperature and PH. Enzymes will work well only at certain conditions. In the human body, enzymes work best at 37 ÂșC body temperature. The lower the temperature the slower the enzymes works. The PH varies from one organ to the other, in the stomach enzymes works best at a PH of 2 while in the intestines they work best at a PH of 7.5. High temperatures and too alkaline or acidic environment make the enzymes to change their shape, which in turn alters the active site’s shape making it hard for substrates to bind to them.

For proper body functioning, enzymes need to be slowed or stopped in a process known as inhibition.

The functioning of an enzyme can be inhibited by:

  1. Competitive inhibitors – a molecule blocks the active site making the substrates compete for the enzymes.
  2. Non-competitive inhibitors – an inhibitor binds on other parts of the enzyme, not the active site to reduce how it works.
  3. Irreversible inhibitors – a molecule binds with an enzyme to permanently inactivate it.
  4. Uncompetitive inhibitors – inhibitors bing the active site and the substrate to increase the time the product takes to be released from the active site.

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