BBC - GCSE Bitesize: What are enzymes?

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Science

Enzymes

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Enzymes are biological catalysts. There are optimum temperatures and
pH*pH*: /Scale of acidity/alkalinity. pH below 7 = acidic, pH above 7 =
alkaline/ values at which their activity is greatest. Enzymes are also
proteins, and usually denatured above about 45ºC.

Enzymes are important in respiration. Aerobic respiration releases energy
from glucose.

** What are enzymes? **

Enzymes are biological catalysts - catalysts are substances that increase
the rate of chemical reactions without being used up. Enzymes are also
proteins*proteins*: /organic compounds 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 are folded into complex shapes that allow smaller
molecules to fit into them. The place where these *substrate* molecules fit
is called the *active site*


Source: www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/enzymes/enzymes1.shtml


what are enzymes


Enzyme - Wikipedia, the free encyclopedia

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** Enzyme **

From Wikipedia, the free encyclopedia
Jump to: navigation, search
"Biocatalyst" redirects here. For the use of natural catalysts in organic
chemistry, see Biocatalysis.
Human glyoxalase I. Two zinc ions that are needed for the enzyme to
catalyze its reaction are shown as purple spheres, and an enzyme inhibitor
called /S/-hexylglutathione is shown as a space-filling model, filling the
two active sites.

*Enzymes* /ˈɛnzaɪmz/ are large biological molecules responsible
for the thousands of chemical interconversions that sustain life.^[1]^[2]
They are highly selective catalysts, greatly accelerating both the rate and
specificity of metabolic reactions, from the digestion of food to the
synthesis of DNA. Most enzymes are proteins, although some catalytic RNA
molecules have been identified. Enzymes adopt a specific three-dimensional
structure, and may employ organic (e.g. biotin) and inorganic (e.g.
magnesium ion) cofactors to assist in catalysis.

In enzymatic reactions, the molecules at the beginning of the process,
called substrates, are converted into different molecules, called products.
Almost all chemical reactions in a biological cell need enzymes in order to
occur at rates sufficient for life. Since enzymes are 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
(/E/[a]^‡) for a reaction, thus dramatically increasing the rate of
the reaction. As a result, products are formed faster and reactions reach
their equilibrium state more rapidly. Most enzyme reaction rates are
millions of times faster than those of comparable un-catalyzed reactions.
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


Source: en.wikipedia.org/wiki/Enzyme

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