Enzymes

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Enzymes

Mr Potter

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Lesson Objectives

Enzyme unit overview

What are they?

How they work

Activation energy

What controls their activity

Rates of reaction

Substrate/enzyme concentrations

Temperature, pH

Enzyme inhibitors

Practical to demonstrate “Catalase” activity in different tissue samples

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Previous related topics covered?

Enzyme controlled reactions?

Proteins?

Lipase, protease, pectinase, amylase etc?

“Lock & Key” molecular structures?

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By the end of the unit you should be able to:-

Explain enzymes as Globular Proteins which act as catalysts

Explain their catalytic action in terms of lowering activation energy

Describe examples of enzyme-catalysed reactions

Discuss factors affecting reaction rates and inhibition

Describe how to investigate these effects experimentally

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Enzymes:-

Are defined as a BIOLOGICAL catalyst i.e. something that speeds up a reaction. Up to 1012 fold

Usually end in ‘…ase’.

Discovered in 1900 in yeasts. Some 40,000 in human cells

Control almost every metabolic reaction in living organisms

Are globular proteins coiled into a very precise 3-dimentional shape with hydrophilic side chains making them soluble

Possess an active site such as a cleft in the molecule onto which other substrate molecules can bind to form an enzyme-substrate complex

Once the substrate has been either synthesised or split, enzymes can be re-used.

Do not ‘create’ reactions

Widely used in industrial cleaning

Often require co-factors (co-enzymes) to function – metal ions, or vitamin derivatives

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Amylase + starch substrate

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How do enzymes work?

Reaction Mechanism

In any chemical reaction a substrate is converted into a product.

In an enzyme catalysed reaction the substrate first binds to the active site of the enzyme to form the enzyme-substrate complex

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Molecule Geometry

Substrate molecule fits into the enzyme like a lock & key.