Enzymes

Question 1

How are enzymes and chemical catalysis the same?

Answer 1

They speed up chemical reactions by lowering the activation energy.

Question 2

Why do cells use enzymes?

Answer 2

To lower the activation energy of biochemical reactions to greatly increase the rates of reaction.

Question 3

How are enzymes structured?

Answer 3

Folded into a very unique 3D structure with a ‘pocket’ called active site where the reaction will take place.

Question 4

What are the two aspects specific to enzymes?

Answer 4

1. They are specific for a very small number of substrates.
2. Enzymatic activity is often regulated by the cell.

Question 5

How are enzymes specific to one substrate?

Answer 5

The electrical charges of the amino acid R-groups in the active site are complementary to those of the enzyme’s substrate.

Question 6

How does an enzyme catalyze a reaction?

Answer 6

1. The substrate or substrates enter the active site.
2. The enzyme changes shape, promoting a reaction.
3. The product is released, and the enzyme returns to its original shape.

Question 7

What are the four major mechanisms by which the cell can regulate its enzymes?

Answer 7

1. Synthesis based on need.
2. Synthesis of inactive enzymes.
3. Allosteric regulation.
4. Competitive inhibition.

Question 8

What is composed in the enzyme regulation method: synthesis based on need?

Answer 8

If the cell needs the reaction, it will create enzymes.

Question 9

What is composed in the enzyme regulation method: synthesis of inactive enzymes (proenzymes)?

Answer 9

The cell makes enzymes in advance but in an inactive form, changing form to make it active when needed.

Question 10

What is allosteric regulation?

Answer 10

• “allo” means “other than”
  some enzyme have places other than the active site where allosteric regulator molecules can bind to them
• when they bind, they cause the enzyme to change shape
• it can cause the enzyme to change so that its active site have the correct shape (allosteric activation) or lose its correct shape (allosteric inhibition)
  like an on/off button

Question 11

What is competitive inhibition?

Answer 11

• Some molecules can mimic the normal substrate of the enzyme and bind to the active site instead
• This blocks the active site because normal substrates can’t get in (so: no reaction or wrong reaction)