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Biological catalysts

Enzyme structure

Proteins made up of long chains of amino acids folded into a specific shape. Any factor affecting enzyme shape affects enzyme activity.


A substance that speeds up a chemical reaction but is not used up in that reaction.

Enzyme Functions

Control cellular reactions and Enable reactions to occur with less energy.

Enzymes are Specific

A different enzyme is needed for each reaction as different enzymes have particular shapes to match each substrate.

Cell activity

Is determined by which enzymes are active at a certain time. Can be altered by removing specific enzymes and synthesising new ones.


Breaks down disaccharides to monosaccharides.


Breaks down starch into maltose.


Digests complex sugars and starches.

Active Site

The part of the enzyme to which the substrate binds. Each site fits only one substrate molecule.

Lock and Key Model

Substrate fits perfectly into active site of enzyme. (Explains Enzyme Specificity)

Induced Fit Model

Shape of the active site is slightly changed to allow substrate to bind to enzyme.

Factors affecting Enzyme Activity

Enzyme and Substrate concentrations, Temperature, pH

Effect of Enzyme Concentration

Rate of reaction increases with enzyme concentration, provided substrate is in excess.

Effect of Substrate Concentration

Rate of reaction increases with substrate concentration until all active sites are in use. (After which there is no change)

Effect of Temperature

Increasing temperature causes more movement, thus causing a higher collision frequency and therefore enzyme action.

37 C

Temperature at which human enzymes work best


When an enzyme has lost its shape and therefore cannot function

Heat Denaturation

Permanent distortion of the active site caused by heat, rendering the enzyme inactive.

Optimum Temperature

Temperature at which the Rate of Reaction is at a maximum.

Critical Temperature

Point at which heated enzymes, if cooled, will regain their activity.

Optimum pH

pH at which the Rate of Reaction is at a maximum.

Enzyme Inhibitor

A substance that changes the shape of an enzyme and makes it unable to bind to a substrate

Hydrogen Peroxide

Substrate used in Enzyme Activity Experiments


Enzyme used in Enzyme Activity Experiments

pH buffers

used to maintain constant pH in Enzyme Activity Experiments

Water baths

used to maintain constant temperatures in Enzyme Activity Experiments

How rate of reaction is measured

the volume of foam that is produced in a set period of time

How enzyme is denatured

source of enzyme (celery) is boiled for 5 minutes

Unboiled enzyme

Control used in Heat Denaturation of an Enzyme Experiment


A vessel in which products are made by biological organisms or their enzymes

Immobilised Enzymes

Enzymes which are attached to each other, to insoluble materials or enclosed in a membrane or gel.

Advantages of immobilised enzymes

Easy harvesting of product / Easy recovery of enzymes for Reuse / Greater enzyme stability.


Enzyme is attached to an insoluble surface e.g. ceramics / glass / plastics.

Membrane Enclosure

Enzyme is enclosed in a porous membrane.

Gel Entrapment

Enzymes are trapped in the fibres of the gel.

Direct Cross Linking

Enzyme molecules are joined to each other to form a polymerised enzyme.


enzyme used in Enzyme immobilisation experiment

Sodium alginate

used in Enzyme immobilisation experiment to immobilise the yeast

Calcium chloride solution

used in Enzyme immobilisation experiment to harden the bound yeast into balls


substrate used in Enzyme immobilisation experiment


product made in Enzyme immobilisation experiment

Making fructose

Glucose Fructose by Glucose isomerase


Used in soft drinks.


Enzymes used to change penicillin into new antibiotics.

Sewage Treatment

Recycled and Reused enzymes are used instead of bacteria.

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