Enzymes Flashcards

1
Q

What type of molecule are enzymes?

A

Globular proteins

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2
Q

What do enzymes act as?

A

Catalysts

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3
Q

What do enzymes do and how do they do it?

A

Speed up reactions by lowering activation energy

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4
Q

What shape do enzymes have and why do they have it?

A

Specific 3D shape due to the sequence of amino acids in the primary structure

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5
Q

What specific region is functional in in an enzyme?

A

Active site

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6
Q

What is the molecule called that an enzyme can act on?

A

Substrate molecule

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7
Q

What do the enzyme and substrate fit together to form?

A

Enzyme substrate complexes

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8
Q

What model explains enzyme action?

A

Induced fit

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9
Q

What are the the 5 main stages of induced fit?

A
  1. Active site forms as the enzyme and substrate interact
  2. The proximity of the substrate leads to a change in the enzyme which forms the functional active site
  3. The enzyme is flexible and moulds itself around the substrate and its general shape alters in the presence of a substrate
  4. As it changes shape it puts strain on the substrate molecule which distorts bonds in the substrate to lower the activation energy needed to break the bond
  5. Colliding with a substrate is a change in the enzymes environment and so its shape changes due to induced fit.
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10
Q

What are the two ways to measure enzyme catalysed reactions?

A
  1. Formation of products of the reaction

2. Disappearance of the substrate

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11
Q

Why is the initial rate of reaction on a product time graph so quick?

A

Lots of substrate and no product at first so the enzyme and substrate molecules randomly collide and the substrate molecules easily bind to empty active sites and make many successful collisions forming many enzyme substrate complexes. The active sites are filled and substrate is broken down into products.

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12
Q

Why does the product time graph begin to curve/ level off and get slower then stop?

A

Substrate decreases and product increases so it is more difficult for substrate molecules to bind as there are fewer substrate molecules and product gets int he way. It takes longer for the substrate to be broken down so rate of formation slows. Then all substrate is used up no new product can be formed.

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13
Q

How do you measure rate of change from a curve on a graph?

A

Draw a tangent and work out the gradient.

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14
Q

How do you work out the gradient?

A

Rise divided by run

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15
Q

How do you find the rate of reaction?

A

1 divided by time.

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16
Q

Why does temperature initially increase the rate of reaction?

A

More kinetic energy and vibrations so more successful collisions between the enzyme and substrate molecules which increases the number of enzyme substrate complexes.

17
Q

Why is the rate of reaction the highest at the optimum temperature for the enzyme?

A

Maximum amount of kinetic energy so maximum number of successful collisions and max amount of enzyme substrate complexes are formed

18
Q

Why does the rate of reaction decrease after the enzymes optimum temperature?

A

Decrease in kinetic energy so the number of successful collisions decreases as well as the number of enzyme substrate complexes. The hydrogen bonds break which denatures the protein so the active site changes shape and the reaction slows and stops.

19
Q

What is the effect of small changes in ph on an enzyme?

A

Small reversible changes causing inactivation

20
Q

What effect do extreme changes in ph have on an enzyme?

A

Permanent reversible changes as the hydrogen and ionic bonds are broken which denatures the protein so the active site changes shape and the substrate is no longer complementary.

21
Q

Why is the intial rate of reaction quick when you increase the substrate concentration?

A

More substrate is available so there is a greater chance of successful collisions so more enzyme substrate complexes are formed. When it reaches the max rate of reaction all the active sites are filled.

22
Q

Why does the effect of substrate concentration graph level off? And what is the point called where it begins to level off? How do you make it go up again?

A

The point of saturation there is excess substrate and not enough enzyme so the substrate concentration has no effect. To make it go up again add more enzyme.

23
Q

Why does enzyme concentration increasing initially increase the rate if reaction?

A

Increased number of enzymes proportionally increases rate of reaction as more enzyme substrate complexes are formed.

24
Q

Why does the enzyme concentration graph level off? How do you increase it again?

A

If the substrate is already being used as rapidly as it can be by the enzyme molecules or if the enzyme is in excess it wont continue to increase. To increase it again add more substrate.

25
Q

What shape are competitive inhibitors?

A

Similar molecular shape to the substrate

26
Q

What do competitive inhibition do?

A

Bind to active sites

27
Q

If substrate concentration increases what happens to the effect of the competitive inhibitor?

A

Decreases

28
Q

What happens when a competitive inhibitor leaves an active site?

A

Another molecule can take its place

29
Q

If the competitive inhibitor has a greater concentration will it take longer or shorter for all the substrate molecules to fill the active sites?

A

Longer

30
Q

Where do non competitive inhibitors bind to?

A

A binding site that is not the active site

31
Q

What do non competitive inhibitors do to active sites and what does that mean for substrate molecules?

A

Alter the shape of the active site so substrate molecules can no longer occupy them

32
Q

What effect does increased substrate concentration have on a non competitive inhibitor? Is the max rate of reaction ever reached?

A

No effect and the max rate of reaction is never reached.