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2.4 Enzymes
Biological Catalysts
Enzymes are biological catalysts that speed up metabolic reactions and remain unchanged at the
end of the reaction. The number of reactions that an enzyme can catalyse per second is known as
the turnover number
Active site the indented area on the surface of the enzyme…

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Amylase is produced in salivary glands to digest polysaccharides
Trypsin is made in the pancreas and digests proteins in the small intestine

Prosthetic groups ­ a cofactor that is permanently bound by covalent bonds to an enzyme
E.g. Zinc ion bound to the active side of carbonic anhydrase…

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B12 Cobalamin Pernicious anaemia (progressive and fatal)
Folic acid Tetrahydrofolate Megablastic anaemia ( large irregular erythrocytes)
Nicotinamide, B3 NAD NADP Pellagra (diarrhoea, dermatitis and dementia)

Pantothenate, B6 Coenzyme A Elevated bloodplasma triglyceride levels
Thiamine, B 1 Thiamine Beriberi (confusion, irregular heartbeat, muscular
pyrophosphate weakness, paralysis & heart failure)

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Lockandkey hypothesis

Inducedfit hypothesis

Enzymes lower the activation energy for a reaction.

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Q 10 ­ temperature coefficient = rate of reaction at (T + 10)

C/ rate of reaction at To C
Effect of temperature on enzymes
Extra heat energy causes the molecules to vibrate which increases the rate of successful
collisions between molecules and increases the force with which they…

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Buffers ­ Can donate or accept protons, resist changes to pH

The tertiary structure is alters as the positive
charges on the protons break the hydrogen
bonds that hold the amino acid in an it's
helix shape. The ionic charges are also
altered and so the active site loses its…

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Effect of Enzyme Concentration

If enzyme concentration is increased the enzyme and substrate swap roles as limiting factors.
Enzyme synthesis ­ genes for synthesising particular enzymes can be switched on or off depending
on a cells needs
Enzyme degradation ­ Cells degrade old enzymes to regulate the metabolism in the…

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side. It blocks the active site and prevents forming. The active site of the enzyme no
enzymesubstrate complexes. longer has the complementary shape to its

End product inhibition ­ when enzyme catalysed reactions are regulated by the final product
molecule acting as an inhibitor for the first enzyme in…

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inflammation and nerve more calcium ions to enter the risk of strokes and heart
sensitivity. the cells. attacks in patients who've
It is also used as a blood thinner Calcium ions increase muscle previously had a myocardial
and to reduce stroke risk. contraction and strengthens infarction.
the heartbeat.

Protease inhibitor…


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