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Year 12 DIgestion & Absorption > Enzymes > Flashcards

Flashcards in Enzymes Deck (20)
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1

Name the 2 mechanisms used to explain how enzymes work.

Lock and key
Induced fit

2

Describe the shape of the active site and substrate.

Complementary.

3

How do enzymes catalyse reactions?

Reduce the activation energy of the reaction.
Puts strain on the bond to be broken

4

What happens when an enzyme becomes denatured?

Hydrogen bonds break.
Changes tertiary shape of enzyme.
Changes shape of active site.
Substrate no longer fits into active site.
No ES complexes formed.
Reduces rate of reaction.

5

Name two variables that can denature enzymes.

High temperature.
pH too high or low.

6

Describe how low temperatures reduce the rate of an enzyme controlled reactions.

At low temperatures:
Substrate and enzyme molecules have low kinetic energy.
Few successful collisions between substrate and active site.
Fewer ES complexes formed.
Low rate of reaction.

7

How do non-competitive inhibitors reduce the rate of an enzyme controlled reaction?

Non-competitive inhibitor binds to allosteric site on enzyme.
Changes the shape of the active site.
Active site and substrate are no longer complementary.
Reduces number of ES complexes formed.

8

How do competitive inhibitors reduce the rate of an enzyme controlled reaction?

Competitive inhibitor and substrate have similar shape.
Inhibitor fits into the active site.
Substrate at able to enter active site.
Fewer ES complexes formed.

9

Describe the induced fit model of enzyme action

Shape of active site is not complementary to the substrate
Binding of a substrate to the active site causes a conformational change
An enzyme substrate complex forms

10

How does substrate concentration affect the rate of reaction?

if enzyme concentration is controlled -
Rate increases proportionally to the substrate concentration.
Rate levels off when a maximum number of enzyme substrate complexes form at any given time. ie all the active sites are full.

11

How does enzyme concentration affect the rate of reaction?

If substrate concentration is in excess -
Rate increase proportionally to enzyme concentration
Rate levels off when a maximum number of enzyme substrate complexes form at any given time

12

How does pH affect the rate of an enzyme controlled reaction?

Enzymes have a narrow optimum pH range
H+ ions and OH- ions alter the charges on amino acids
Hydrogen and ionic bonds break
Changes tertiary structure
Changes the shape of the active site
Substrate no longer complementary to the active site.

13

Describe the difference in shape between a competitive and non-competitive inhibitors

Competitive - similar shape to substrate
Bind to the active site
Non-competitive - different shape to substrate.
Binds to allosteric binding site

14

Outline how to calculate the rate of reaction from a graph

Plot a graph of dependent variable (y axis) against time (x axis)
Calculate gradient of line or gradient of tangent to a point on the graph

15

Outline how to calculate the rate of reaction from raw data

Change in dependent variable / time

16

Why is it advantageous to calculate the initial rate of reaction?

Represents maximum rate of reaction
Before concentration of substrates decrease or end point inhibition.

17

How can the progress of an enzyme controlled reaction be measured?

Amount of product made over time
Amount of substrate used over time.

18

Explain why an increase in temperature can cause an increase in the rate of an enzyme controlled reaction.

Higher temperature
More Kinetic energy given to enzyme and substrate
Mors successful collisions
more enzyme substrate complexes formed.

19

Many human enzymes have an optimum temperature of 40 oC. Suggest why has the body evolved to have a body temperature of 37 oC

Other non-enzyme proteins might denature at at lower temperature.
More likely that a fever (due to illness) would denature enzymes.
More respiration needed to release sufficient thermal energy to maintain higher body temperature

20

Why does an enzyme denature faster at 60 oC compared to 40 oC

More energy transferred to enzyme
ionic and hydrogen bonds break faster