Enzymes

Living things use different

chemical reactions to get

the energy needed for life

Quick Review of Macromolecules

1. Carbohydrates (C, O, H)

2. Lipids (C, O, H)

3. Proteins (C, O, H, N)

4. Nucleic Acids (C, O, H, N, P)

Proteins: Four Major Functions

1. Support and Structure (Muscles and

tendons)

2. Fight Diseases (White blood cells)

3. Carry nutrients (Red blood cells)

4. Speed up Chemical Reactions

(enzymes)

» 4 levels of protein structure

– Primary – peptide bonds

– Secondary – hydrogen bonds (protein

starts to fold)

– Tertiary and Quaternary – all other types

of bonds create the final functional

shape of the protein

Chemical Reactions » Reactants = substance that is changed

» Products = new substance that forms

– Ex: ATP ADP + P + energy

– Ex: H2O H + OH

• The double arrow means the reaction build and then break down (can do forward and reverse reactions)

» Types

– Exothermic = releases energy (breaks down)

– Endothermic = absorbs energy (builds)

Enzyme definition

• A protein molecule that increases the

speed of a biochemical reaction. (reactions

in the body)

• Enzymes are catalysts inside your body!

What do enzymes do?

• By lowering the activation energy needed, enzymes help to speed up chemical reactions within the body.

• Activation Energy=energy need to start a chemical reaction.

• Ex: A ball on top of a hill will not start rolling unless someone pushes it (input of energy), just like reactions will not occur unless energy is added to start it.

An enzyme is a

catalyst.

Examples of Enzyme Reactions

1. Enzymes in your mouth called amylase speed up the chemical reaction for breaking down sugars.

2. Enzymes called lactase speed up the chemical reaction for breaking down the milk sugar called lactose.

3. Enzymes in the mitochondria called ATPase speed up the chemical reaction of breaking down ATP to release energy.

Amylase protein Structure

Amylase Reaction

Amylase Enzyme Diagram

1. Was the water environment hypotonic,

hypertonic or isotonic? Explain.

Lactase Protein Structure

Reaction Catalyzed by Lactase

Diagram of Lactase Catalyzing

Lactose Intolerance

Enzyme names

• Lipase

• Protease

• Amylase

• ATPase

• Lactase

• Cellulase

• Do you see a pattern?

How do enzymes work?

1. A substrate binds to an enzyme’s active

site. The substrate fits in a specific

position or location, like a lock and key.

Active site

How do enzymes work

2. Binding of the substrate to the enzyme

causes the substrates shape to change

and bonds to either break or form.

Active site Bonds have broken and shape has changed.

How do enzymes work

3. The chemical reaction is complete when

the product, a new substance, is formed.

Active site

Bonds have broken and shape has changed.

Products have

formed

How do enzymes work?

4. Enzymes can work in both directions,

either breaking a substrate or building a

product.

Active site

Bonds have broken and shape has changed.

Examples of Enzyme Reactions

1. The enzyme lactase breaks the

substrate lactose (milk sugar) into the

products galactose and glucose.

2. The liver enzyme alcohol dehydrogenase

breaks the substrate alcohol down into

the product aldehyde.

Alcohol Dehydrogenase Protein Structure

Asian Flush

Important Properties of Enzymes

1. Enzymes are never used up.

2. Enzymes can be used over and over again.

3. Enzymes and Substrates fit like a lock and key.

4. Enzymes reduce the amount of activation

energy needed to start the reaction

5. Enzymes are a type of protein.

6. Enzymes speed up biochemical reactions.

7. Enzyme reactions can go in both directions.

Factors Affecting Enzyme Function

» Increase in temperature = enzyme denatures

(breaks bonds) which changes the shape of

the enzyme

– The enzyme can no longer bind to

substrates

» Decrease in temperature = slows molecular

movement and causes less collisions and

reactions to occur

– Does not denature the enzyme

Factors Affecting Enzyme

Function » Change in pH to more acidic or more basic

= enzyme denatures

– The exception are enzymes in the

stomach that need an extremely acidic

environment to function properly

» Increase enzyme or substrate concentration = rate (speed) of reactions increases

– More people working to clean up, means the clean up happens faster

» Addition of inhibitors (molecules that cause the substrate not to bind to the enzyme = decreases the rate of the reaction

– Competitive inhibitors will bind to the active site instead of the substrate

– Noncompetitive inhibitors will bind to another place on the enzyme, but will cause a change in the shape of the active site

» Video: Activation Energy

» Video: Enzyme Characteristics

» Video: Amoeba Sisters

» Video: How Enzymes Work