B M 4 : Enzyme Action

Question 1

What are enzymes and what do they do?

Answer 1

Biological catalysts

- speed up chemical reactions by acting as biological catalysts

Question 2

At what levels do enzymes catalyse metabolic reacts?

Answer 2

Cellular level (respiration) 
And for the organism as a whole (digestion on mammals)

Question 3

At can enzymes affect? Give an example

Answer 3

The structures in an organism

- they’re Involved in the production of collagen, important protein in the connective tissue of mammals

Question 4

Where can enzyme action take place?

Answer 4

-intercellular (within cells)
OR
-extracellular (outside cells)

Question 5

What are enzymes classes as?

Answer 5

Proteins

Question 6

Which part of the enzyme does the substrate molecule bind to?

Answer 6

Active wire, which has a specific shape

Question 7

Why are enzymes highly specific?

Answer 7

Due to their tertiary structure

Question 8

What do enzymes lower?

Answer 8

The activation energy of a reaction

Question 9

What’s activation energy?

And what’s it often provided as?

Answer 9

The amount of energy that needs to be supplied to the chemicals before the reaction will start
-heat

Question 10

What’s it form when a substrate fits into an enzymes active site?

Answer 10

An enzyme-substrate complex

Question 11

What causes enzymes to lower the activation energy?

Answer 11

The formation of an enzyme-substrate complex

Question 12

One reason Why an enzyme-substrate complex lowers the activation energy?

Answer 12

• if two substrate molecules need to be joined, being attached to an enzyme brings them closer together
• reducing any repulsion between the molecules so they can bond easily

Question 13

Another reason why an enzyme-substrate complex lowers the activation energy

Answer 13

If enzyme catalysts a breakdown reaction, putting into the active site puts strain on bonds in the substrate
- so substrate molecule breaks up more easily

Question 14

Lock and key model?

Answer 14

• substrate fits into enzymes active site
• enzyme-substrate complex formed
• substrate broken down products released after reaction
• enzyme is unchanged after reaction

Question 15

Does the lock and key model give the full story?

Answer 15

No

Question 16

What does new evidence show?

Answer 16

The enzyme-substrate complex changes shape slightly to complete the fit
- locks substrate more tightly to the enzyme

Question 17

What’s the induced fit model?

Answer 17

• substrate fits into enzyme active site
• as substrate binds the active site changes shape slightly
• enzyme-substrate complex formed
• products released

Question 18

What do enzymes properties relate to?

Answer 18

Their tertiary structure

Question 19

Are enzymes very specific ?

Answer 19

Yes

Question 20

Why are enzymes specific?

Answer 20

Because only one complementary substrate will fit into the active site

Question 21

What determines the enzymes active site?

Answer 21

The tertiary structure

Question 22

Do all enzymes have different tertiary structure and so different active sites

Answer 22

Yes

Question 23

What does it mean if tertiary structure is altered?

Answer 23

Shape of active site will change

• enzyme substrate won’t fit active siren
• so enzyme-substrate complex can’t be formed
• enzyme can’t carry out its function

Question 24

How can the tertiary of the enzyme be changed?

Answer 24

By changes in pH or temperature

Question 25

What’s the primary structure of a protein determined by?

Answer 25

A gene

- so If a mutation occurs in that gene, it could change the tertiary structure of the enzyme produced