2.1.4 Enzymes

Question 1

what is an enzyme

Answer 1

A biological catalyst used to speed up the rate of biochemical reactions without
being used up or permanently altered

Question 2

what are the properties of enzymes

Answer 2

• tertiary structure
• enzymes are specific
• enzyme structure can be disrupted by high temps and extremes of pH

Question 3

what is the roles of enzymes in catalysing reactions

Answer 3

• enzymes lower the activation energy so the rate of reaction increases

Question 4

what are intracellular enzymes

Answer 4

enzymes that act within the cells that produce them

Question 5

what is an example of an intracellular enzyme

Answer 5

-catalase
-this enzyme catalyses the breakdown of hydrogen peroxide into oxygen and water
-this prevents the accusation of toxic hydrogen peroxide inside cells

Question 6

what are extracellular enzymes

Answer 6

enzymes that act out the cells that produce and secrete them

Question 7

what is an enzyme of an extracellular enzyme

Answer 7

amylase
- this is secreted by the salivary glands, pancreas, and small intestine to break down starch into maltose
Trypsin
- this is secreted by the pancreas into the small intestine to break down proteins into smaller polypeptides

Question 8

describe the mechanism of enzyme action
( how the enzyme binds with the substrate)

Answer 8

• enzymes have unique tertiary structure which determines the shape of the active site
• the active site is complementary to the substrate
  -the substrate binds to the active site to form an enzyme-substrate complex
• temporary bonds form between the R groups within the active site and the substrate
• these bonds lower the activations energy to help break down the substrate into product
• the products are released from the active site, leaving the enzyme free to be used again

Question 9

describe the lock and key model hypothesis

Answer 9

this model suggest that the substrate fits perfectly into the enzymes ative site in the same way that a key irs into a lock

Question 10

describe the induced-fit hypothesis

Answer 10

-in this model, the substrate does not perfectly into the enzymes active site.
- the active site slightly changes shape slightly as the substrate enters the enzyme.
- this puts a strain on the substrates bonds which lowers the activation energy

Question 11

what factors effect enzymes activity

Answer 11

Temperature
pH
Substrate concentration
Enzyme concentration

Question 12

explain the effect of pH on enzyme activity

Answer 12

• in acidic conditions, H+ ions break the ionic/hydrogen bonds and denature enzymes
• the optimum pH is the pH the enzymes work the fastest at
• in alkaline conditions, OH- ions break ionic bonds or hydrogen bonds and denatures enzymes

Question 13

explain the effect of temperature on enzyme activity

Answer 13

-The molecules have more kinetic energy, causing more collisions and enzyme-substrate complexes.
-The optimum temperature is the temperature this enzyme works fastest at.
- there are more collisions between the enzyme and the substrate so there are more successful collisions between the enzymes active site and the substrate
-Too much kinetic energy causes the active site to change shape and the enzyme denatures.

Question 14

what is the temperature coefficent

Answer 14

The temperature coefficient (Q10) is a value that shows how much the rate of reaction changes when the temperature is increased by 10°C.

Q10 = R2/R1

Where:

R2 = The rate of reaction at the higher temperature (+10°C).
R1 = The rate of reaction at the lower temperature.

Question 15

explain the effect of enzyme concentration on enzyme activity

Answer 15

• at the beginning there are more enzyme molecules which allows for more collisions, so more successful collisions between the substrate and active site
• this forms more enzyme substrate complexes
• until all the substrate molecules available are being acted upon and substrate concentration becomes the limiting factor

Question 16

explain the effect of substrate concentration on enzyme activity

Answer 16

• there are more substrate molecules, so more collisions, so more successful collisions between the active site of the enzyme and the substrate.
• so forms more enzyme-substrate complexes
• all the enzymes are taken up by substrates, so the enzyme concentration becomes the limiting factor and the rate of reaction stays constant

Question 17

what is a cofactor

Answer 17

non-protein substances that bind to enzymes to increase their activity

Question 18

what are the two types of cofactors

Answer 18

• coenzymes
• prosthetic group

Question 19

what is an example of a cofactor

Answer 19

Cl- is a cofactor for amylase

Question 20

what is a coenzyme

Answer 20

These are organic cofactors and are usually derived from vitamins

Question 21

what is a prosthetic group

Answer 21

These are cofactors that are tightly bound to enzymes

Question 22

what is an example of a prosthetic group

Answer 22

Zn2+ is a prosthetic group for the enzyme carbonic anhydrase

Question 23

what is an inhibitor

Answer 23

molecules that bind to enzymes to reduce their activity

Question 24

what is a reversible inhibitor

Answer 24

These form weak bonds (e.g. hydrogen or ionic) with the enzyme.

Question 25

what is an irreversible inhibitor

Answer 25

an molecule thay forms strong bonds (eg covalen) with the enzyme

Question 26

what is a competitive inhibitor

Answer 26

it is an inhibitor which binds to the active site of an enzyme to prevent enzyme-substrate complexes

Question 27

how does a competitor inhibitor work

Answer 27

• competitive inhibitors have a similar shape to the active site
• and so will being to the active site of the enzyme.
• means the substrate wont be able to bind which reduces the formation of enzyme-substrate complexes.
• this reduces the rate of enzyme catalysed reactions
  -most competitive inhibitors are reversible as they only bind temporarily to the enzyme

Question 28

how does the substrate concentration effect competitive inhibitors

Answer 28

• the higher the substrate concentrations, the more likely it is for the substrates to bind to the active sites, rather than the inhibitor molecule.
• this reduces the effect of the competitive inhibitor

Question 29

what is a non-competitive inhibitor

Answer 29

• Non-competitive inhibitors bind to enzymes away from the active site (allosteric site) to prevent enzyme-substrate complexes.

Question 30

How does a non-competitive inhibitor work

Answer 30

• the inhibitor will bins to the allosteric site
• this changes the tertiary structure of the enzyme causing the enzymes active site to change shape
• this means the substrate and the enzymes active site is no longer complementary so the substrate and enzyme can no longer bind
• this causes less enzyme-substrate complex’s formed so the rate of the enzyme-catalysed reaction decreases

Question 31

How does the substrate concentration effect non-competitive inhibitors

Answer 31

• non-competitive inhibitors does compete with the substrate to bond to the active site.
• this means that increasing the amount of substrate will have no effect on the rate of reaction