what are enzymes?

Answer 1

Enzymes are proteins that catalyze (i.e. accelerate) chemical reactions. In these reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts these into different molecules, the products. Almost all processes in the cell need enzymes in order to occur at significant rates. Since enzymes are extremely selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell.

Like all catalysts, enzymes work by lowering the activation energy for a reaction and thus dramatically accelerating the rate of the reaction. By binding the transition-state conformation of the substrate/product molecules, the enzyme distorts the bound substrate(s) into their transition state form, thereby reducing the amount of energy required to complete the transition. Most natural enzymes accelerate their reaction many millions of times faster compared to the uncatalyzed reaction. As with all catalysts, enzymes are not consumed by the reactions they catalyze, nor do they alter the equilibrium of these reactions. However, enzymes do differ from most other catalysts by being much more specific. Enzymes are known to catalyze about 4,000 biochemical reactions.[1] Not all biochemical catalysts are proteins, since some RNA molecules called ribozymes can also catalyze reactions.

Enzyme activity can be affected by other molecules. Inhibitors are molecules that decrease enzyme activity, and activators are molecules that increase activity. Drugs and poisons are often enzyme inhibitors. Enzyme activity is also affected by temperature, pH, and the concentration of substrate. Some enzymes are used commercially, for example, in the synthesis of antibiotics. In addition, some household products use enzymes to speed up biochemical reactions (e.g., enzymes in biological washing powders break down protein or fat stains on clothes; enzymes in steak tenderizers break down long meat proteins, making them easier to chew).

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Answer 2

Enzymes are proteins that catalyze (i.e. accelerate) chemical reactions. Enzymes are biochemical catalysts. In these reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts these into different molecules, the products. Almost all processes in the cell need enzymes in order to occur at significant rates. Since enzymes are extremely selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell.

Answer 3

Well,
one of the factors that defines a living thing from an inanimate object is the organism's ability to carry out chemical reactions that are crucial for its survival. Even one-celled organisms are capable of hundreds of chemical reactions within their cell walls. Imagine the infinite amount of reactions that a large organism such as a human carries out. None of these reactions are possible without enzymes.

Enzymes are biological catalysts or assistants. Enzymes consist of various types of proteins that work to drive the chemical reaction required for a specific action or nutrient. Enzymes can either launch a reaction or speed it up. The chemicals that are transformed with the help of enzymes are called substrates. In the absence of enzymes, these chemicals are called reactants.

To illustrate the speed and efficiency of enzymes, substrates can be transformed to usable products at the rate of ten times per second. Considering that there are an estimated 75,000 different enzymes in the human body, these chemical reactions are performed at an amazing rate. On the other hand, in the absence of enzymes, reactants may take hundreds of years to convert into a usable product, if they are able to do so at all. This is why enzymes are crucial in the sustenance of life on earth.

Generally, enzymes work on substrates in one of three ways: substrate orientation, physical stress, and changes in substrate reactivity. Substrate orientation occurs when an enzyme causes substrate molecules to align with each other and form a bond. When an enzyme uses physical stress on a substrate, it in effect grips the substrate and forces the molecule to break apart. An enzyme that causes changes in substrate reactivity alters the placement of the molecule’s electrons, which influences the molecule’s ability to bond with other molecules.

Enzymes have active sites where they come into contact with particular substrates. The catalytic properties of enzymes are a cyclic process. Once a substrate has come into contact with the active site of an enzyme, it is modified by the enzyme to form the end product. Once the process is complete, the enzyme releases the product and is ready to begin the process with new substrates. Enzymes are never wasted and always recycled.

The absence of enzymes is responsible for many diseases. In humans, a tragic disease called phenylketonuria (PKU), which causes severe mental retardation and even death in infants, is the result of the absence of one type of enzyme. Tay-Sachs disease is a similarly tragic result of an enzyme deficiency. It causes retardation, paralysis, and often death in early childhood when left untreated.

Our ability to alter enzymes by inhibiting their functioning abilities has resulted in hundreds of life saving drugs. One example is penicillin, a well-known antibiotic that can cure syphilis, pneumonia, and other illnesses. Penicillin works by bonding to the active sites of the disease-causing bacteria’s enzymes, ultimately destroying the bacteria’s ability to survive and reproduce.

Answer 4

Enzymes are biological catalysts: this means that they speed up the chemical reactions in living things. Without enzymes, our guts would take weeks and weeks to digest our food, our muscles, nerves and bones would not work properly and so on - we would not be living!

A catalyst is any substance which makes a chemical reaction go faster, without itself being changed. A catalyst can be used over and over again in a chemical reaction: it does not get used up. Enzymes are very much the same except that they are easily denatured (destroyed: but do NOT use this word since the protein molecule is not broken down into amino-acids, it just loses it shape and will not work any more) by heat. Our enzymes work best at body temperature. Our enzymes also have to have the correct pH.

All enzymes are made of protein; that is why they are sensitive to heat, pH and heavy metal ions. Unlike ordinary catalysts, they are specific to one chemical reaction. An ordinary catalyst may be used for several different chemical reactions, but an enzyme only works for one specific reaction.

Human saliva contains an enzyme called amylase. This enzyme helps to turn starch into a sugar called maltose. When you swallow a mouthful of food, the amylase stops working because it is much too acid in the stomach pH 2. Amyalse works best in neutral or slightly alkaline conditions, i.e. at about pH 7. When your food gets into the small intestine, more amylase is made by the pancreas and this turns the remaining starch into maltose. Another enzyme (maltase) turns all this maltose into glucose. Glucose is then absorbed into the blood.

Enzymes in the human alimentary canal and what they digest:

Enzyme Substrate
Amylase Starch
Maltase Maltose
Sucrase Sucrose
Lipase Fats
Pepsin Proteins

All animals, green plants, fungi and bacteria produce enzymes: so enzymes are not just about digesting food. The enzymes which we use to digest our food are extra-cellular, that means they are found outside cells. We also have enzymes inside our cells; these are intra-cellular enzymes. Enzymes are used in ALL chemical reactions in living things; this includes respiration, photosynthesis, movement growth, getting rid of toxic chemicals in the liver and so on.

Viruses are rather different, but you do not need to know much about them for GCSE, so just make sure that you don't catch any!

Enzymes must have the correct shape to do their job. They are made of proteins, and proteins are very easily affected by heat, pH and heavy metal ions. Some people say that enzymes work like a key in a lock. If the key has been twisted by heat, or dissolved in acid or stuck up with chewing gum it will not work. Enzymes change their shape if the temperature or pH changes, so they have to have the right conditions. Copper ions are poisonous: if you get copper ions in your blood they will block up some of the important enzymes in red and white blood cells.

Answer 5

they are biological catalyst also they take part in any of the reactions . basically they are proteins. one enzyme can act on a particular substrate that is they are highly specific for e.g zymase ,urease etc the method of action is lock and key mechanism that is each enzyme fits on certain active site of the substrate.

Answer 6

Enzymes are biological catalyst(speed up chemical reaction) which is made of protein.It can build up or break down.

Answer 7

enzyme is a substance that decreases the activation energy of a reaction....it accelerates the biological reactions

Answer 8

enzymes are special proteins that accelerate a chemical reaction.

Answer 9

http://en.wikipedia.org/wiki/Enzyme

Answer 10

chemical substances that act as bio catalysts in the chemical reactions