Enzyme ActionObjective: To understand the role of enzymes in the body and how they function.

Outcomes:Recall the function of enzymes.

Describe the structure of enzymes.

Compare the two different models that explain how enzymes work.

Keywords

Active siteSubstrateEnzyme-substrate complexLock and key modelInduced fit model

Thursday 13 April 2023

EnzymesGlobular proteins that catalyse chemical reactions in living organisms (biological catalysts):

PropertiesSpecific (tertiary protein structure)Increase rate of the reaction

Unchanged at the end of the reaction

Need themReactions too slow to maintain life

A substrate is a reactant which binds to an enzyme.When a substrate or substrates binds to an enzyme, the enzyme catalyzes the conversion of the substrate to the product.e.g. Sucrase is an enzyme that binds to sucrose and breaks the disaccharide into fructose and glucose.

Enzymes are specific

The active site of an enzymes is typically a pocket or groove on the surface of the protein into which the substrate fits.The specificity of an enzyme is due to the fit between the active site and that of the substrate.

Models of enzyme action

The lock and key model

The induced fit model

Use page 31 and 32 to create a table/diagram/notes summarising the differences between these two models of enzyme action.

Substrate molecules

EnzymeActive site

Product

The lock and key model

Reaction happens (bonds either made or broken)

Enzymes have a specific 3D structure

Enzyme-substrate complex

Enzyme is rigid.

But…Other molecules could bind to enzymes at different sites.

This altered the activity of the enzyme.

The enzyme was flexible.

Models of enzyme actionThe induced fit model• The active site fits to the

substrate, and the enzyme changes shape slightly.

• This interaction is called induced fit.

Enzyme Action

The lock and key model

The induced fit model

Scientists often try to explain their observations by producing a representation of how something works. This is known as a scientific model.