Properties And Types Of Enzymes Biology Essay

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Properties And Types Of Enzymes Biology Essay

Enzymes were discovered by a German chemist Eduard Buchner near the end of the 19th century He had been trying to extract a fluid for medicinal use from yeast however the yeast extract kept going bad He then decided to add sugar to the yeast however the yeast converted the sugar into alcohol which is also known as fermentation Buchner investigated into this and soon found out that living cells were not responsible for this fermentation and that it was caused by the fluid that was trying to be extracted from the yeast The word enzyme was coined for the active ingredients in the juice that promoted fermentation Although enzyme literally means in yeast it is now however being used as the collective noun for several hundreds of compounds that have shown to have a catalytic action on specific chemical reactions

Enzymes are biological or organic catalysts made up of protein They catalyse increasedecrease the rate of chemical reactions without themselves being chemically changed at the end of the reaction It can therefore be used repeatedly and so is effective in small amounts They essentially work by lowering the activation energy of the reactions and hence allowing the reaction to place at a quicker rate In enzymatic reactions the molecules are the start of the process are called substrates and the converted molecules the products

Properties of enzymes

Enzymes have the following properties

Enzymes alter the rate of chemical reactions without themselves being chemically changed at the end of the reaction

Enzymes are very potent Since enzymes are very specific a small amount of an enzyme is capable of catalysing a huge chemical reaction

Enzymes are affected by temperature Enzymes are inactive at low temperatures Increasing the temperature increases the activity of the enzymes There is an optimum working temperature at which certain enzymes work best This is normally between 3742 degree centigrades However a high temperature anything above 45 degree centigrades normally destroys the active sites of the enzymes and causes it to denature This permanently damages the enzyme and they become functionless

Enzymes are affected by pH Certain enzymes work best in acidic conditions whereas certain enzymes function better in alkaline conditions For example pepsin works best in the stomach where the pH is below 7 however intestinal enzymes work better in coditions of pH of above 7

Some enzymes may require a compound to be bound to them before they can catalyse chemical reactions These compounds are called coenzymes

Enzymes can work in either directions Metabolic reactions are reversible and the direction in which the reaction goes depends on the amounts of substrate and products present The reaction will proceed from left to right until an equilibrium is reached between the substrates and products Also if there is a large amount of products then the reverse reaction starts and hence causes the product to be split up until again equilibrium is established

Lock and Key Induced Fit Hypothesis

Although enzymes have a large size however they only have a small region that is functional This is known as the active site Active sites can be described as depressions on the surface of the enzyme Only a few of the amino acids of the enzyme molecule make up this active site the remainder are used to maintain its overall threedimensional shape The active site is the site where the substrate binds onto the enzyme and only substrates with a particular molecular shape will have any chance to bind effectively with the particular enzyme This is the reason why enzymes are specific in their actions as they can only bind to specific substrate molecules

Another idea which arose from the lock and key hypothesis is the induced fit hypothesis that suggests that the enzyme alters its shape slightly to ensure that the enzyme molecules bind tightly with the substrate molecule However once the product or substrate leaves the active active

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