Cells & Enzymes

Enzymes

Made of protein Present inall living cells

Converts substratesinto products

Biological catalysts

Increase the rate of chemical reactions

Remain unchanged by chemical reaction

This term really means two things:

ANABOLISM and CATABOLISM

METABOLISM

ANABOLISM

“ TO BUILD” molecules as in the biosynthesis of polymers..

We ingest food digest to monomers and THEN via ANABOLISM we make larger molecules

“TO BREAK APART “

Example: Glycogen, (starch) stored in the liver when needed for energy, is converted to glucose ( monomers).

So during catabolism large molecules are broken into smaller molecules.

Catabolism …then is to..

ProductSubstrate

Chemical Reactions

A chemical reaction takes place when one or substances is chemically changed into one or more different substances.

Chemical reactions take place in cells all the time.

Enzyme

Catalase

Hydrogen peroxide

Water + oxygen

Manganesedioxide

Catalyst

Enzymes and Chemical ReactionsEnzymes can speed reactions by lowering the amount of energy

needed for a chemical reaction

Catalysts

A catalyst is a substance which speeds up a chemical reaction, without itself being changed by the reaction.

When a catalyst is present, less energy is needed to get the chemical reaction started.

When a catalyst is present, the speed of the chemical reaction is faster.

3. Although a catalyst helps a chemical reaction to happen, it is unchanged at the end of the reaction.

Biological Catalysts

The biological catalyst present in the cytoplasm of plant and animal cells that speeds up the breakdown of hydrogen peroxide is called CATALASE.

Hydrogen peroxide

Oxygen + watercatalase

REACTANTS PRODUCTS

enzyme

2.2 Nature of Enzymes

The biological catalyst present in the cytoplasm of plant and animal cells that speeds up the breakdown of hydrogen peroxide is called CATALASE.

Catalase cannot speed up any other reaction. It is SPECIFIC to this reaction.

CatalaseHydrogen peroxide

Water + oxygen

One Enzyme – One Reaction

There are thousands of different enzymes in your body.

Why are there so many different enzymes?

Each enzyme has its own unique protein structure and shape, which is designed to match or COMPLEMENT its substrate.

Lock & Key Hypothesis

An enzyme only acts on one type of substance, or substrate.

Therefore, the enzyme is said to be SPECIFIC to its one substrate. The shape of the active site (binding site) of the enzyme, matches the shape of the substrate. Allowing the two molecules to bind during the chemical reaction.

This theory of enzyme action is called the ‘lock-and-key’ hypothesis.

MOVIE

Different enzymes for different jobs

Enzymes involved in breakdown reactions

Enzyme and substrate separateEnzyme-substrate complexEnzyme and products separate

Enzymes involved in synthesis reactions

Enzyme and substrates separateEnzyme-substrates complexEnzyme and product separate

2.3 Using a Control

Why is it necessary to include a control experiment in an investigation?

A control is an experiment that allows a comparison within an investigation in order to ensure that the conclusions drawn from the results are valid.

Enzymes involved in breakdown reactions

CatalaseHydrogen peroxide Water + Oxygen

AmylaseStarch

LipaseFat Fatty acids + Glycerol

PepsinProtein Amino acids

2.5 Effect of High Temperature

Notes on Denaturation Notes on Optimum temp

Optimum conditions are the conditions at which an enzymes works best

Rate of reactions may be affected by temperature and pH

2.5 Effect of High Temperature

Notes on Denaturation

What happens to the activity of an enzyme at high temperatures?

Movie

Effect of pH on enzymes

When the pH changes outwith optimal conditions, the shape of the active site of the enzyme alters and the enzyme is denatured.

Effect of pH on enzyme activity

Most enzymes work best at a pH close to neutral (pH7), but there are some exceptions. Pepsin, an enzyme found in the stomach, has an optimum pH of 2.

Enzyme Substrate Product(s) Degradation or synthesis?

Amylase Starch Maltose

Catalase Hydrogen peroxide

Oxygen and water

Pepsin Protein Amino acids

Phosphorylase Glucose-1-phosphate

Starch s

Lipase Fat Fatty acids

Enzyme Summary