Enzymes Flashcards

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1
Q

What are enzymes?

A

globular proteins that act as biological catalysts

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2
Q

How does an enzyme act as a biological catalyst?

A

alter rate of chemical reaction by lowering activation energy required without undergoing permanent change themselves

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3
Q

What is required to start a chemical reaction?

A

-must collide with sufficient energy
-energy of products must be lower than substrates/reactants
-minimum amount of energy to start reaction-activation energy

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4
Q

What is the structure of an enzyme?

A

Specific region- active site

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5
Q

What is an active site?

A

forms small depression within the much larger enzyme molecule

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6
Q

What is the active site made up of?

A

relatively small number of amino acids

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7
Q

What is the molecule that the enzyme acts upon called?

A

substrate

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8
Q

What is formed when the active site and substrate collide?

A

enzyme-substrate complex

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9
Q

How is an enzyme substrate complex formed?

A

substrate and active site collide
substrate held within active site that temporarily form bonds between certain amino acids of substrate and active site

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10
Q

What does the lock and key enzyme model suggest?

A

enzyme active site specific shape to particular substrate
enzyme active site and substrate are exactly complimentary
when substrate collides with active site an enzyme substrate complex is formed

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11
Q

What does the enzyme induced fit model propose?

A

active site and substrate not EXACTLY complimentary
active site forms as enzyme and substrate interact
proximity of substrate alters shape to form functional active site
enzyme moulds itself around substrate
enzyme substrate complex is formed

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12
Q

What two changes are most frequently measured to determine the length of enzyme-catalysed reactions?

A

-formation of products
-reduction in starch concentration

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13
Q

How can we measure the change in a rate of reaction?

A

measure gradient at chosen point

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14
Q

How can we obtain a gradient from an enzyme-catalysed reaction ?

A

equal to gradient of tangent to curve at point
tangent- point at which straight line touches the curve without cutting across it
normal line- line that pass through a point at 90•
gradient- A/B

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15
Q

How do we create a control when measuring the rate of an enzyme-catalysed reaction?

A

enzyme and substrate concentration constant
all possible inhibitors absent
active site and substrate mustn’t be complementary

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16
Q

How does temperature affect the rate of an enzyme-catalysed reaction?

A

rise in temperature, increase in kinetic energy of molecules
molecules more likely to collide as moving rapidly
enzyme and substrate in contact more often in a given time
more successful collisions, more enzyme substrate complexes, increases rate of reaction
HOWEVER LIMITING…
temperature rise causes bonds to break
active site changes shape
harder to form enzyme substrate complex, slower rate
higher temperature, enzyme denatured (permanent) no enzyme substrate complex as cannot function

17
Q

What is the pH of a solution?

A

Measure of its hydrogen ion concentration

18
Q

What does each enzyme have in terms of pH?

A

An optimum pH

19
Q

How does pH affect enzyme action?

A

-alters charges on amino acids that form active site therefore substrate can longer bind for e-s complex
-depending on significance of pH change, bonds maintaining tertiary structure break and active site changes shape

20
Q

How does enzyme concentration affect the rate of reaction?

A

Excess of substrate-increase in amount of enzyme-proportionate increase in rate of reaction
If substrate limiting-increase in enzyme concentration-not enough substrate available for increase in active site-no effect on rate

21
Q

How does substrate concentration affect the rate of reaction?

A

Increase in substrate concentration- more substrate available to bind to active site (more opportunities)-rate of reaction increases-more e-s complexes formed-substrate becomes limiting factor-no further effect

22
Q

What are enzyme inhibitors?

A

Substances that directly or indirectly interfere with function of active site

23
Q

What is a competitive inhibitor?

A

Substances which bind directly to active site of enzyme

24
Q

What is a non-competitive inhibitor?

A

Substances which bind indirectly to the enzyme (allosteric site) which changes the shape of the active site

25
Q

How does competitive inhibition work?

A

Molecule structurally similar to substrate competes and binds to active site
Prevents substrate from binding
Effects are reversible as inhibitor not permanently bound to active site

26
Q

How can we prevent the affects of competitive inhibition?

A

Increase substrate concentration, effect of inhibitor reduced

27
Q

How does non-competitive inhibition work?

A

Inhibitor binds to allosteric site
Binding to allosteric site alters shape of active site
Non-competitive inhibitors do not compete with substrate
Change in active site shape stops substrate from binding

28
Q

Why does increasing substrate concentration not effect non-competitive inhibition?

A

Substrate and non-competitive inhibitor do not compete for the same site. Substrate for active site whereas non-competitive inhibitor for allosteric site