Enzymes

Question 1

Enzymes structure

Answer 1

• it is a globular proteins
• have a specific 3D shape according to their sequence of amino acids
• active site made up of small number of amino acids.
• substrate held with active site by forming temporary bonds between amino acids of the active site and groups on the substrate

Question 2

Enzymes action model

Answer 2

Induced fit model:
- active site forms as the enzymes an substrate interact
- enzyme is flexible, it can mould itself around the substrate to change shape of active site to fit
- a change in environment of the enzyme lead to a change in the enzymes that forms the active site.

Question 3

What happens when enzymes changes its shape?

Answer 3

• enzyme put a strain on the substrate molecule, the strain distorts a particular bond or bonds in the substrate which lead to lower activation energy needed originally to break the bond.

Question 4

Definition of catalyst

Answer 4

• it can alter the rate of chemical reaction without under going permanent changes themselves.
• can be used repeatedly, effective in small amounts
  E.g. enzymes speed up reactions

Question 5

Factors affect enzyme action

Answer 5

• temperature
• PH
• enzymes’ concentration
• substrates’ concentration

Question 6

Enzymes’ work depends on whether :

Answer 6

• it comes into physical contact with its substrate
• it has an active site which fits the substrate

Question 7

What is the changing measurements of an enzyme catalysed reaction?

Answer 7

• the formation of products
  OR
• the reduction of substrates
  Based on time course- how long it takes

Question 8

What is the term used to describe the shape of active site and substrates as ?

Answer 8

They are complementary

Question 9

Effect of temperature on enzymes

Answer 9

• increases kinetic energy of molecules so enzyme and substrates molecules move quicker and more frequent collision so more effective collision to form enzyme substrate complex so rate of reaction increases

Question 10

Effect of temperature rising

Answer 10

• cause hydrogen bonds and other bonds to break which changes the shape active site
• slows down reaction at 45degrees

Question 11

Denaturation

Answer 11

• is a permanent change and once occurred, enzymes does not function again = falling curve on the graph
• usually after optimum temp 40 degrees in human body
• high temp = high metabolic rate, but requires extra energy like food to maintain high temp.
• other proteins except enzyme can denature at high temp e.g. during illness

Question 12

PH of a solution

Answer 12

• is a measure of its hydrogen ion concentration

Question 13

PH on enzyme action

Answer 13

• in/decrease of PH can affect rate of reaction
• it alters the change on amino acids that make up the active site so substrates no longer fit in = enzyme substrate complex cannot be formed
• may cause the bonds of enzymes’ tertiary structure to break = active site changes shape

Question 14

Active site of enzymes

Answer 14

• the arrangement of it partly determined by hydrogen and ionic bond between amino and carboxyl group of polypeptides
• the change in H+ ions affect the bonding = active site to change shape

Question 15

Why does enzyme able to work at very low concentration?

Answer 15

• because it can repeat the procedure on another substrate once it acted on an active site
• means it is not being used up in a reaction

Question 16

Effect of increasing enzyme concentration ( excess substrates)

Answer 16

• more enzyme means more active sites that substrate can act on so now increase enzyme conc can cause excess substrates now be acted upon so ROR increase

Question 17

Effect of increasing enzyme concentration ( limiting substrate)

Answer 17

• not efficient to supply all enzymes active site so increase conc will have no effect on ROR
• ROR stay constant level bec existing enzyme already used up with available substrate

Question 18

Effect of increasing sub conc

Answer 18

• increase ROR
  bec. more substrate added, activities being filled and at full capacity until all of them work as fast as they can -) ROR max. -) So excess substrates will have no effect on ROR

Question 19

What is the name of the point between flat and steep line of ROR graph

Answer 19

Point of saturation

Question 20

Definition of enzyme inhibitors

Answer 20

Substances that directly or indirectly interfere with the functioning of acitve site of enzyme and so reduce activity

Question 21

Types of enzyme inhibitor

Answer 21

• Competitive inhibitor
• Non competitive inhibitor

Question 22

Structure of competitive inhibitor

Answer 22

• has molecular shape SIMILAR to the substrate, allow them to occupy the acitve site, compete with the orginal substrate
• block acitve site

Question 23

Effect of competitive inhibitor

Answer 23

• reversible/ irreversible reaction
• sub conc. inverse proportional to effect of inhibitor
• greater inhibitor conc. Longer time it takes to get away from the A.S

Question 24

Why is sub.conc inverse proportional to effect of inhibitor

Answer 24

Because inhibitor not permeantly bound to active site, so when it leaves, a sub or another inhibitor can take its place, depending on how much each conc are

Question 25

Difference between competitive and non competitive inhibitor

Answer 25

Competitive inhibitor bind to active site of enzyme. Non CI bind to enzyme’s allosteric site other than active site

Question 26

Effect of non competitive inhibitor

Answer 26

• can alter shape of enzyme and its active site ( tertiary structure of proteins) so that substrate no longer fit in and enzyme cannot function
• distort active site

Question 27

Effect of sub conc on non competitive inhibitor

Answer 27

• no effect
  Bec. They are not competing for the same site