Enzymes Flashcards

1
Q

Name the 2 mechanisms used to explain how enzymes work.

A

Lock and key
Induced fit

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2
Q

Describe the shape of the active site and substrate.

A

Complementary.

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3
Q

How do enzymes catalyse reactions?

A

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

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4
Q

What happens when an enzyme becomes denatured?

A

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

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5
Q

Name two variables that can denature enzymes.

A

High temperature.
pH too high or low.

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6
Q

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

A

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

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7
Q

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

A

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 enzyme substrate complexes formed.

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8
Q

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

A

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

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9
Q

Describe the induced fit model of enzyme action

A

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

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10
Q

How does substrate concentration affect the rate of reaction?

A

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.

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11
Q

How does enzyme concentration affect the rate of reaction?

A

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

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12
Q

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

A

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.

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13
Q

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

A

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

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14
Q

Outline how to calculate the rate of reaction from a graph

A

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

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15
Q

Outline how to calculate the rate of reaction from raw data

A

Change in dependent variable / time

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16
Q

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

A

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

17
Q

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

A

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

18
Q

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

A

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

19
Q

Many human enzymes have an optimum temperature of 40 oC.

Suggest why has the body evolved to have a body temperature of 37 oC

A

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
Q

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

A

More energy transferred to enzyme
Ionic and hydrogen bonds break faster