Enzymes - VIP molecules.

Mr Mark GretgrixWedderburn College

Description/ DefinitionBiological catalysts, made of

protein, coded for by DNA.allow reactions to occur more

easilyhelp cells perform reactions

that would normally occur very slowly, or not at all

do not get changed during reaction, they can be recycled

found in cytoplasm and in various organelles

can be secreted and work outside the cell

are involved in breakdown and synthesis

Examples:

Urease - catalyses the breakdown of urea

Catalase - breakdown of hydrogen peroxide

Polymerase - DNA synthesis

Cell Metabolism.Refers to all the chemical

reactions in a cell.Involves complex sequences of

reaction with each one controlled by an enzyme. The product of one reaction becomes the reactant of the next reaction.

By controlling the availability of enzymes, cells can control which chemical reactions will take place at any one time.

Mode of Operation

Enzymes act to orient the reactant/s so that they behave exactly as required for the reaction to occur.

Substrate Product

Eg a decomposition reaction:

Sucrose Glucose + fructose:

The enzyme has a specific shape, it can only be used to catalyse one type of reaction.

The site at which the reaction takes place in the enzyme is called the ACTIVE SITE.

Rate of Reaction - depends on:Temperatureamount of reactants and

products presentpHpresence of other

substances

Temperature:

As temperature increases the number of collisions between molecules increases.

--> increases enzyme activity

As temperature decreases the number of collisions between molecules decreases.

--> decreases enzyme

activity

At higher temperatures the protein structure ‘overheats’, the enzyme is ‘denatured’, the active site cannot function. --> decrease in enzyme activity

Amount Reactants/ Products- enzymes work in equilibrium reactionsEnzymes operate to create a

balance between reactants and products

To increase enzyme activity reactants need to be available and products need to be removed.

Amount of enzyme present:

An increased amount of enzyme will increase the reaction rate.

This will be affected by the concentration of the substrate available.

pH

Affects hydrogen bonding in the protein which affects the active site

Each type has its optimal pH, activity decreases away from this value

Other substancesBlock the active site by binding

to it. eg. poisons

Alter the shape of the active site by binding onto another part of the enzyme

Co-enzymes

Small molecules needed to help the enzymes in their activity

eg. Some vitamins, trace elements