BIOLOGY 102

ENZYMES

SB1.b. Explain how enzymes function as catalysts.

What is an enzyme?

Also called a biological catalyst

Protein that speeds up the rate of a reaction.

Not changed during the reaction.

Used over and over until the reactant is used up.

Why are enzymes important? Decreases the amount

of energy needed (activation energy) for a reaction to occur.

As a result, the reaction happens faster.

Green line is reaction without enzymeRed line is reaction WITH enzyme.

What would happen if we did not have enzymes or they did not work properly?

You would DIE! No enzymes =

reactions happening too slowly so body can’t get what it needs to survive.

Each enzyme has a specific shape which causes it to bind with specific reactants

Parts of an Enzyme-Substrate Complex:

Substrates- reactants that fit with enzyme

Active site- site on enzyme that substrates bind to

Products- created from combining of substrates. This is what leaves the enzyme

How does an Enzyme Work?

How Does an Enzyme Work?

Because only SPECIFIC substrates will fit in SPECIFIC enzymes they are often compared to a LOCK & KEY MODEL

How Does an Enzyme Work? Enzymes work one of two

ways– Bind two reactants to make

one product (see picture on right)

– Break bonds in large molecule to make many smaller ones (see picture below)

Two reactants bind together to make one product

One reactant is broken apart to make two products. Orange structure is enzyme, green & blue parts in first part of picture are substrates.

What may alter enzyme functioning?

pH, salt concentration, temperature

All will DENATURE enzyme. Changes its shape so it no

longer accepts substrates so can’t create products.

This would slow down/stop reactions from happening in body.

Great Website to show Enzyme activity

Can you answer these questions about the picture below? (Check answers on next page.)

1. What type of macromolecule is an enzyme?

2. What is another name for enzyme?

3. What is the enzyme term for #2?

4. What is the enzyme term for the site on the enzyme where the sucrose attaches?

5. What is added at #3?

6. What is the enzyme term for the glucose & fructose created at #4?

7. Has the enzyme changed in this reaction?

8. What types of factors could denature the enzyme?

9. What will happen if the enzyme is denatured?

Can you answer these questions about the picture below? ANSWERS

1. What type of macromolecule is an enzyme? Protein

2. What is another name for enzyme? Catalyst

3. What is the enzyme term for #2? Reactant or substrate

4. What is the enzyme term for the site on the enzyme where the sucrose attaches? Active Site

5. What is added at #3? Water (H2O)

6. What is the enzyme term for the glucose & fructose created at #4? Products

7. Has the enzyme changed in this reaction? No- has same shape so can be reused

8. What types of factors could denature the enzyme? pH, temperature, salt9. What will happen if the enzyme is denatured? Active site is changed so reactants can no longer fit

into enzyme so reaction can’t happen. This means you can no longer break down sucrose to get the glucose & fructose so cells can’t absorb these glucose & fructose molecules to use them. Cell may “starve” for these molecules.

Can you answer these questions about the graph below? (Check answers on next page.)

This graphs shows how an enzyme functions at different pH levels.

1. This enzyme works best at which pH?

2. Would you find this enzyme in your stomach or blood? How do you know?

3. What would happen to the amount of product made if the pH rose to 13?

Can you answer these questions about the graph below? ANSWERS

This graphs shows how an enzyme functions at different pH levels.

1. This enzyme works best at which pH? pH 7

2. Would you find this enzyme in your stomach or blood? Blood How do you know? Stomach has acidic environment so would need an enzyme that works best at an acidic pH level.

3. What would happen to the amount of product made if the pH rose to 13? The amount of product would decrease b/c the enzyme does not work well at that pH.

1. Enzymes are compared to a lock & key because

a. They open up cells and let stuff in

b. They have very specific active sites so can only participate in a specific reaction

c. They destroy specific enzymes

2. The structure labeled biological catalyst is

a. a substrate

b. an Enzyme

c. a ribosome

3. How does a lower temperature (refrigeration) affect the rate of enzyme activity?

a. It speeds it up b. It slows it down c. It has no effect

4. During the canning process, heat is used to destroy bacteria in food. How does this affect enzymes?

a. They are not affected b. They are denatured c. They multiply

5. What is the optimum pH for this enzyme?

a. 3 b. 7 c. 14

6. Will this enzyme function any differently at a pH of 16?

a. Yes b. no