QUICK QUESTIONS

What is the difference between a fibrous and a globular protein?

Why is the structure of a protein related to its function?

What are the tests for reducing sugars, lipids, starch and proteins.

Name the three chemical groups of an amino acid.

TODAY’S LESSON –ENZYMES – ENZYME ACTION

We need to be able to answer:1. Explain how enzymes speed up chemical reactions.2. Describe how the structure of enzyme molecules

relates to their function.3. Explain the lock and key model of enzyme action.4. Explain the induced-fit model of enzyme action

Language we will be using:1. Catalyst2. Substrate3. Products4. Enzyme substrate complex5. Activation energy6. Active site

WHAT ARE ENZYMES?

Enzymes are proteins generated by an

organism to speed up a reaction – they

are biological catalysts.

Each enzyme has a specific job, either

breaking or forming bonds of reactants

to form substrates.

Enzymes have an active site where only a

specific reactant can fit.

WHAT CAN YOU REMEMBER ABOUT ENZYMES?

key factors interactive animation

Globular structureEnzymes are globular

proteinsThey have a

complex 3

dimensional

Tertiary

shape

Enzymes

This shape allows them

to match the substrate

Enzyme Substrate

This is the LOCK and KEY

theory. The enzyme is not used

up and is available for further

reactions.

Lock and Key

ENZYME ACTION – LOCK AND KEY MODEL

What is the lock and key model?

Why is it a good model?

Why is it a bad model?

Do you think there is anything

wrong with it?

INDUCED FIT THEORY

WHY DO CHEMICAL REACTIONS OCCUR?

WHY DOESN’T DIAMOND CHANGE TO

GRAPHITE?

WHAT IS A CATALYST?

starch

glucose

HOW DO ENZYMES LOWER ACTIVATION

ENERGY?

1.Break down reaction – binding to the

active site of an enzyme puts strain on a

molecule meaning less energy is needed

to break the bonds within it

2.Build up reaction – binding of substrates

to the active site brings them close

together and in the correct orientation,

this reduces repulsion between them

and so less energy is needed to form a

bond between them

PAST PAPER QUESTION

TODAY’S LESSON –ENZYMES – ENZYME ACTION

We need to be able to answer:1. Explain how enzymes speed up chemical reactions.2. Describe how the structure of enzyme molecules

relates to their function.3. Explain the lock and key model of enzyme action.4. Explain the induced-fit model of enzyme action

Language we will be using:1. Catalyst2. Substrate3. Products4. Enzyme substrate complex5. Activation energy6. Active site

WHY ARE ENZYMES IMPORTANT?

SYLLABUS

(a) state that enzymes are globular proteins, with a

specific tertiary structure, which catalyse metabolic

reactions in living organisms;

(b) state that enzyme action may be intracellular or

extracellular;

(c) describe, with the aid of diagrams, the mechanism

of action of enzyme molecules, with reference to

specificity, active site, lock and key hypothesis,

induced-fit hypothesis, enzyme-substrate complex,

enzyme-product complex and lowering of activation

energy;