2.4 Enzymes

Question 1

What are the physical features of enzymes?

Answer 1

• Globular proteins- Spherical with lots of alpha helix
• Generally soluble in water due to R groups
• Biological catalysts

Question 2

What is the definition of activation energy?

Answer 2

• Minimum amount of energy required for a reaction to take place

Question 3

How do enzymes work?

Answer 3

Reduce activation energy through complimentary fit between enzyme and substrate.

Question 4

What is the induced fit hypothesis?

Answer 4

That there is a change in shape of the enzyme in response to a substrate binding

Question 5

What are the steps of the induced fit hypothesis?

Answer 5

1. Substrate collides with active site
2. Enzyme molecule;e changes shape slightly so active site fits more closely around substrate
3. Enzyme substrate complex formed **
4. Destabilises substrate producing product
5. Enzyme product complex formed

Question 6

What is meant by the term ‘anabolic reactions’?

Answer 6

Build up larger molecules e.g. protein synthesis

Question 7

What are catabolic reactions?

Answer 7

Break down larger molecules

Question 8

What are intracellular enzymes?

Answer 8

Act within cells e.g. synthesis of polymers

Question 9

What are extracellular enzymes?

Answer 9

Make substrates outside of cells
Released from cells

Question 10

What do extracellular enzymes allow for?

Answer 10

Use of polymers
Single cell use it to absorb glucose

Question 11

How is starch digested?

Answer 11

Starch polymers are broken down into maltose by amylose in saliva
Maltose is broken down into glucose in small intestine

Question 12

How are proteins digested?

Answer 12

Trypsin is a protease which catalyses digestion of proteins into smaller peptides
Broken down further into amino acids
Trypsin is produced in pancreas

Question 13

What is the effect of temperature on enzymes?

Answer 13

Kinetic energy causes bonds to vibrate
More likely to collide successfully

Question 14

What happens to enzymes if temperatures goes to high?

Answer 14

Bonds vibrate too much and break causing enzymes to lose 3D shape and denature

Question 15

What does denature mean?

Answer 15

Enzyme has permanently changed shape

Question 16

What are thermophiles?

Answer 16

Living organisms adapted to withstand hotter temperatures?
Enzymes are more stable and more resistant to change

Question 17

What are cryophiles?

Answer 17

Enzymes that function in very cold environments.
Enzymes have more flexible structures and are less stable

Question 18

What is the effect of pH on enzymes?

Answer 18

H + ions interact with polar groups and charged R groups where bonds break and substrate no longer fits active site

Question 19

What is renaturation?

Answer 19

Where if pH of solution returns to optimum enzymes will return to original shape

Question 20

What is V max?

Answer 20

Maximum rate of reaction
All active sites are occupied by substrate particles

Question 21

What is the effect of increasing substrate concentration?

Answer 21

• Increases number of collisions between enzymes and substrate
• Increases number of enzyme substrate complexes which in turn increases rate of reaction

Question 22

How can V max be increased?

Answer 22

Increasing the limiting reactant or temperature e

Question 23

What is the effect of increasing enzyme concentration?

Answer 23

• Increases number of active sites available
• Increases number of enzyme substrate complexes increasing rate of reaction

Question 24

What is an inhibitor?

Answer 24

Any substance/molecule that slows down the rate of an enzyme controlled reaction by affecting the enzyme molecule

Question 25

What are competitive inhibitors?

Answer 25

• Similar shape to substrate
• Occupy active site to form enzyme-inhibitor complexes
• number of enzyme substrate complexes decreases causing rate to decrease
• Most don’t bind permanently

Question 26

What are non competitive inhibitors?

Answer 26

• Bind elsewhere on the enzyme at the allosteric site
• Affects tertiary structure
• Level of inhibition depends on concentration of inhibitor
• Many bind permanently
• Used in insecticides

Question 27

What is an allosteric site?

Answer 27

Another binding point on an enzyme

Question 28

What is end product inhibition?

Answer 28

Product of one reaction is an inhibitor to the enzyme that produced it

Question 29

What are co-factors?

Answer 29

Non protein components
Bind temporarily at allosteric site
Obtained from diet e.g. Fe +

Question 30

What are co-enzymes?

Answer 30

• Organic co-factor
• Many derived from vitamins e.g. NAD
• Carry chemicals between enzymes.

Question 31

What are prosthetic groups?

Answer 31

• Also a cofactor
• Bind permanently

Question 32

How are enzymes activated?

Answer 32

• Need a change in tertiary structure
• Can be activated either by co factors or a change in pH