Chapter 4 - Enzymes

ENZYMES

catalase + H2O2 LIVER H 2 O + O2

ARE ENZYMES IMPORTANT ?!?

IMPORTANCE OF ENZYMES 



Majority of reactions in living organisms are enzyme controlled Fatal damage e.g. toxins buildup, food cannot be absorbed

WHAT ARE ENZYMES? 

A biological catalyst which can alter or speed up a chemical reaction, without itself being chemically changed at the end of the reaction.

ENZYME SOURCES 

BACTERIA



FUNGI



PLANTS



ANIMALS

WHAT ARE ENZYMES MADE OF? 

PROTEIN

all enzymes are made of protein BUT not all proteins are enzymes 

SUBSTRATE 

SUBSTRATE = substance on which enzymes act



E.g. starch, proteins, fats etc

CLASSIFICATION 

According to the chemical reactions they catalyze. ENZYMES SUBSTRATE CARBOHYDRASE carbohydrate cellulose CELLULASE protein PROTEASE lipids LIPASE AMYLASE starch

WHY MUST FOOD BE DIGESTED? too large  cannot be absorbed by body cells  DIGESTION: Large, insoluble food molecules broken down into small, soluble & diffusible molecules 

USES OF ENZYMES 

BREAKDOWN e.g.glucose …. Carbon dioxide + water



SYNTHESIS e.g. amino acids….proteins

CHARACTERISTICS 1. ALTER OR SPEED UP RATE OF REACTION

CHARACTERISTICS 2. VERY POTENT 

Remain unchanged



Can be reused



A small amount for a large amount of chemical reactions

CHARACTERISTICS 3. SPECIFIC e.g. amylase only act on starch e.g. protease only act on protein

CHARACTERISTICS 4. REVERSIBLE REACTIONS

A+B

C+D

ENZYME 

ACTIVE SITE = a position on the enzyme where the substrate binds

HOW DO ENZYMES WORK? THE LOCK AND KEY HYPOTHESIS

HOW DO ENZYMES WORK? 

SPECIFICITY



Due to SHAPE



ACTIVE SITE



After substrate fits in, enzyme alters shape slightly

APPLICATIONS

DETERGENT

FRUIT JUICE pectinase

PAPAYA PAWPAW

papain MEAT TENDERIZER

oil spills

FACTORS AFFECTING ENZYME ACTIVITY 1. TEMPERATUREmost

Enzyme activity

active

OPTIMUM TEMPERATURE inactive

denatured

Temperature

DENATURATION 

High temperature, acids & alkalis



Shape changed



3D structure lost



ACTIVE SITE altered



IRREVERSIBLE DESTRUCTION: extreme heat

FACTORS AFFECTING ENZYME ACTIVITY Enzyme activity

2. pH

most active

OPTIMUM pH denatured

denatured

pH

FACTORS AFFECTING ENZYME ACTIVITY Enzyme activity

3. SUBSTRATE & ENZYME CONCENTRATION Y X

Enzyme concentration B Enzyme concentration A

Substrate concentration

LIMITING FACTOR 

Directly affects rate of reaction if quantity is changed

COENZYMES 





Some enzymes require coenzymes NON-PROTEIN organic compounds Most are vitamins (B complex vitamins)

THE END