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Enzymes


They are catalysts; they lower the activation energy thus increasing the rate at which reactions
occur
...
(They are made up of proteins)



Tertiary Structure; folded into a specific shape
...




They have a globular active site
...




The shape of the enzyme will determine which substrate it will act on
...




The shape of an enzyme can be altered or denatured and the enzymes won’t function as it is
supposed to
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

Complete Active site and co-factor together are called- Holoenzyme



The protein part without the co-factor is – Apoenzyme



METABOLISM= ANABOLISM + CATABOLISM

Examples of Non-Protein ‘’partners’’ of enzymes
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S -> P
In an enzyme-catalysed reaction, the substrate;
1
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Converted into product while attached to enzyme
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Product is released

Molecule Geometry
-Lock and Key mechanism
Induced fit mechanism;
-

This is the change in shape of the active site of an enzyme, so it binds more exact to the
substrate and an enzyme substrate complex can form
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Energy Changes
Activation Energy (EA); the energy require to start a reaction
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The Active Site can lower EA barrier by two ways:
1
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2
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Factors that affect the rate of enzyme Reactions:
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Temperature

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pH (7-8)

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Enzyme Concentration

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Substrate Concentration

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Covalent modification

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Inhibitors

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Allosteric Effectors

Types of Enzymes:
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Lactase

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Catalase

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ATP-ase

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Glycogen Synthase

Inhibitors: Reduce the rate of enzymatic reactions
-Competitive Inhibitor; - Has similar structure to the normal substrate molecule
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-Non-Competitive Inhibitor; Different in structure from the substrate molecule> Does not fit in active site
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Non- competitive inhibitors reduce the amount of active enzymes
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Allosteric Regulators; May inhibit or stimulate the activity of an enzyme by binding to specific regulatory
sites, Affecting the shape and function of the enzyme
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