1.4 Enzymes

Question 1

what is the shape / structure of enzymes?

Answer 1

tertiary structure 3D shap

Question 2

how is the active site held together?

Answer 2

held by peptide, hydrogen, ionic and disulphide bonds

Question 3

what is the lock and key model?

Answer 3

1. Substrate(s) and the active site of the enzyme come into contact
2. Substrate(s) binds, enzyme-substrate complex forms
3. Reaction takes place, product(s) formed in an enzyme-product complex
4. Product(s) released from the active site. The active site is now free to bind to another substrate

Question 4

what changes occur to the enzyme at the end of the reaction?

Answer 4

no changes, enzyme remains unchanged

Question 5

the induced fit hypothesis

Answer 5

A model of enzyme action which states that once a specific substrate binds to the active site, the enzyme undergoes subtle conformational changes. This puts a strain on the substrate, lowering the activation energy for the reaction

Question 6

when does this reaction occur?

Answer 6

at lower activation energy

Question 7

what are intracellular enzymes?

Answer 7

An enzyme that acts within cells, e.g.
catalase

Question 8

what are extracellular enzymes?

Answer 8

An enzyme that is secreted by cells and
functions outside of cells, e.g. amylase.

Question 9

how does low temperature affect enzymes?

Answer 9

at low temperatures, there are low KE so fewer successful collisions where the substrate is able to enter the active site of the enzyme and form products

Question 10

how does high temperature affect enzymes?

Answer 10

● As temperature increases molecules have more KE
● Molecules moves faster and collide more frequently
● More enzyme-substrate complexes form
● Rate of reaction increases
● Rate peaks at the optimum temperature

Question 11

what happens if the temperature continues to increase?

Answer 11

● Temperature increases above the optimum
● Increased vibrations break hydrogen and ionic bonds in tertiary structure
● Active site changes shape, enzyme is denatured
● No more enzyme-substrate complexes can form
● Rate of reaction decreases

Question 12

How does substrate concentration affect the rate of an enzyme-controlled reaction?

Answer 12

If enzyme concentration is fixed, the rate of
reaction increases proportionally to the
substrate concentration.

Once all active sites become full, the rate of
reaction becomes constant - graph plateaus
(enzyme concentration is a limiting factor)

Question 13

How does enzyme concentration affect the rate of an enzyme-controlled reaction?

Answer 13

If substrate concentration is fixed, the rate of
reaction increases proportionally to the
enzyme concentration.

When all of the substrates occupy active
sites, the rate of reaction remains constant -
graph plateaus (substrate concentration is a
limiting factor)

Question 14

what effect does low substrate conc have?

Answer 14

it becomes a factor that is limiting the rate of reaction

Question 15

what does further increase in substrate conc do?

Answer 15

has no effect as it is no longer the limiting factor

Question 16

when does the rate of reaction become plateaus

Answer 16

when all enzymes have full active sites
the enzyme conc becomes the limiting factor

Question 17

what are the advantages of using immobilized enzymes for blood glucose monitoring?

Answer 17

shows accurate results
the enzyme is more stable
specific / will only give results for glucose
detects very low conc

Question 18

define metabolism ?

Answer 18

The sum of all the enzyme controlled
chemical reactions taking place in a cell

Question 19

State the two main types of reactions that make up metabolism

Answer 19

Anabolic and catabolic reactions.

Question 20

what is anabolism ?

Answer 20

A set of metabolic pathways that
synthesise complex molecules from
smaller, simpler molecules

Question 21

what is catabolism?

Answer 21

A set of metabolic pathways that
breakdown complex molecules into
smaller, simpler molecules

Question 22

what is an enzyme?

Answer 22

● A biological catalyst used to speed up the
rate of intracellular and extracellular
biochemical reactions
● Not used up or permanently altered

Question 23

what is the active site of an enzyme?

Answer 23

A region on an enzyme that is complementary to the shape of a specific substrate. The substrate binds and the reaction takes place.

Question 24

why is the active site described as ‘specific’?

Answer 24

● The 3D structure of each enzyme (including the active site) is unique due to the presence of different side chains and branches
● Only specific substrates complementary to the active site can bind

Question 25

define activation energy

Answer 25

The minimum amount of energy
required for a reaction to take place

Question 26

what is a catalysis?

Answer 26

● An increase in the rate of a chemical reaction using a catalyst (such as an enzyme)
● The catalyst lowers the activation energy of
the reaction

Question 27

What factors affect the rate of an
enzyme-controlled reaction?

Answer 27

● Temperature
● pH
● Substrate concentration
● Enzyme concentration

Question 28

what is a buffer?

Answer 28

A molecule that maintains a constant pH
in a solution when small amounts of acid
(H+) or base(OH-) are added

Question 29

what is a competitive inhibitor ?

Answer 29

A molecule which binds to the active site
of an enzyme, blocking it and preventing
the substrate from binding.

Question 30

Is competitive inhibition temporary or permanent?

Answer 30

Competitive inhibition is generally temporary.
However, in some cases (e.g. aspirin) it may
be permanent

Question 30

Is competitive inhibition temporary or permanent?

Answer 30

Competitive inhibition is generally temporary.
However, in some cases (e.g. aspirin) it may
be permanent

Question 31

How does increasing substrate concentration affect competitive inhibition?

Answer 31

● Increase in substrate concentration
● More substrate than inhibitor
● Rate of reaction increases

Question 32

What is a non-competitive inhibitor?

Answer 32

● An inhibitor which binds to a different part of an enzyme, the allosteric site
● The tertiary structure of the enzyme (including the active site) changes shape
● The active site is no longer complementary to the substrate. The substrate cannot bind and the enzyme is inhibited

Question 33

Is non-competitive inhibition temporary or
permanent?

Answer 33

permanent

Question 34

How does increasing substrate concentration affect non-competitive inhibition?

Answer 34

Increasing the substrate concentration
will not overcome the effect of the
non-competitive inhibitor

Question 35

What are immobilised enzymes?

Answer 35

Enzymes which are attached to an inert,
insoluble material over which the substrate
passes and the reaction takes place.

Question 36

Give an example of an application of
immobilised enzymes

Answer 36

biosenors

Question 37

Why are immobilised enzymes important
in industrial processes?

Answer 37

●Enables enzymes to be reused
● Improves enzyme stability in variable/Extreme temperatures and pH
● Increases the efficiency of reactions