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Biology Exams > Enzymes > Flashcards

Enzymes Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is the active site of an enzyme?

A

The area within the tertiary structure of the enzyme that is complementary to the specific substrate

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2
Q

What is the lock and key hypothesis?

A

The idea that only a specific substrate will fit the active site of the enzyme

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3
Q

What is the induced-fit hypothesis?

A

Weak initial interactions between the enzyme and substrate induce changes in the enzyme’s tertiary structure, which strengthens the binding of the enzyme and substrate

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4
Q

When is an enzyme-substrate complex formed?

A

When the substrate binds to the active site of the enzyme

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5
Q

What is an enzyme-product complex?

A

After the substrate has finished reacting, you are left with a enzyme-product complex

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6
Q

How do enzymes increase rate of reaction?

A

By lowering the activation energy of the reaction. For example they can put strain on the substrate, weakening particular bonds, lowering the energy required to break these bonds

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7
Q

What are intracellular enzymes?

A

Enzymes that act within the cell in which they were made

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8
Q

What is an example of an intracellular enzyme?

A

Catalase, which breaks down hydrogen peroxide in the cell

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9
Q

What are extracellular enzymes?

A

Enzymes that act outside of the cell the cell in which they were made

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10
Q

What are extracellular enzymes often involved in?

A

Digestion

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11
Q

What enzymes are involved in the digestion of starch?

A

Starch to maltose = amylase

Maltose to glucose = maltase

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12
Q

What enzyme is involved in the digestion of proteins in the pancreas?

A

Trypsin

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13
Q

What is the name of enzymes that break down proteins?

A

Proteases (trypsin is an example of a protease)

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14
Q

What is temperature coefficent?

A

How much rate of reaction increases with an increase of 10 degrees celcius

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15
Q

What is temperature coefficent also known as?

A

Q10

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16
Q

What is optimum temperature of an enzyme?

A

The temperature at which the enzyme has the highest rate of activity

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17
Q

What is the impact of increasing the temperature too much?

A

Increasing the temperature causing the enzyme to vibrate more and more, which can eventually cause bonds to break within the enzyme, changing the tertiary structure

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18
Q

What does a change in the tertiary structure mean in terms of enzyme activity?

A

When the tertiary structure changes due to temperature (the enzyme denatures) the active site will no longer be complementary to the substrate; this will cause a rapid drop in enzyme activity

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19
Q

What is the impact of decreasing the temperature on enzyme activity?

A

Enzymes will have less kinetic energy and enzyme activity will be lower, but the drop will be gradual as enzymes are not denaturing, just slowing

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20
Q

What is optimum pH of an enzyme?

A

The pH in which the active site is the correct shape

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21
Q

What happens if the pH changed from the optimum?

A

The tertiary structure will change, meaning the substrate will not fit the active site

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22
Q

What is renaturation?

A

If the pH doesn’t change massively, and returns to the optimum, the enzyme will return to its correct shape

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23
Q

What happens if the pH goes beyond a certain point?

A

If the pH is changed significantly, the structure of the enzyme can be irreversibly altered; the enzyme is now said to be denatured

24
Q

What is Vmax?

A

The maximum rate of reaction at which enzyme or substrate concentration becomes a limiting factor

25
Q

What is the impact of increasing substrate or enzyme concentration?

A

It will increase the rate of reaction up to a plateau

26
Q

Why will the rate of reaction eventually plateau with an increasing substrate concentration?

A

Eventually, all enzyme active sites will be occupied so no more enzyme-substrate complexes can be formed until an active site becomes free

27
Q

Why will the rate of reaction eventually plateau with an increasing enzyme concentration?

A

Eventually, all substrates will have formed enzyme-substrate complexes, meaning enzymes that were additionally added would remain empty

28
Q

What are the two types of enzyme inhibition?

A

Competitive and non-competitive inhibition

29
Q

What is a competitive inhibitor?

A

A molecule that has a similar shape to the substrate of an enzyme, and so can fit into the active site

30
Q

How do competitive inhibitors inhibit enzymes?

A

It occupies the active site, preventing the substrate from entering

31
Q

How do competitive inhibitors impact rate of reaction and Vmax?

A

Competitive inhibitors will slow rate of reaction, but does not change the Vmax of the reaction

32
Q

Example of medicinal use of competitive inhibitors

A

Statins are competitive inhibitors of an enzyme used in the synthesis of cholesterol; statins are prescribed to help people reduce cholesterol levels

33
Q

What is an example of a non-reversible competitive inhibitor?

A

Asprin

34
Q

What are non-competitive inhibitors?

A

Molecules that bind to the allosteric site of the enzyme, acting as an inhibitor

35
Q

How do non-competitive inhibitors inhibit enzyme activity?

A

The binding to the allosteric site changes the tertiary structure of the enzyme, meaning the active site changes shape

36
Q

How can the impact of competitive inhibitors be overcome?

A

If you add enough substate, there will be so much more substrate than inhibitor that the original Vmax can be reached

37
Q

How can the impact of non-competitive inhibitors be overcome?

A

It can’t. Increasing the substrate concentration will not overcome the effect of non-competitive inhibitors

38
Q

What is the impact of non-competitive inhibitors on Vmax?

A

Non-competitive inhibitors will lower the Vmax of a reaction

39
Q

What is end-product inhibition?

A

Where the product of a reaction acts as an inhibitor for the enzyme that produces it

40
Q

What is end-product inhibition an example of?

A

A negative-feedback control mechanism

41
Q

What are cofactors?

A

Non-protein helper component needed by some enzymes

42
Q

What are coenzymes?

A

If a cofactor is organic, it is called a coenzyme

43
Q

What is a source of coenzymes with 2 examples?

A

Vitamins
E.g. vitamin B5 is used to make Coenzyme A
& vitamin B3 is used to make NAD

44
Q

What is an example of a cofactor?

A

Cl- for amylase

45
Q

How are prosthetic groups similar to cofactors?

A

They are required by some enzymes to carry out their catalytic function

46
Q

How are prosthetic groups different to cofactors?

A

Cofactors are loosely bound and are not a permanent feature of the enzyme, whereas prosthetic groups are tightly bound and form a permanent feature of the enzyme

47
Q

What is an example of a prosthetic group?

A

Zn2+ for carbonic anhydrase

48
Q

Why is end-product inhibition important?

A
  • Prevent build-up of, excess / unnecessary
    products; maybe toxic
  • Prevent waste of
    resources / energy
49
Q

Why do end-product inhibitors need to be reversible?

A

They need to be

reversible so more product can be made when it is needed

50
Q

What are precursor enzymes?

A

Enzymes that need to undergo a change in tertiary structure to be activated

51
Q

What 3 ways can the activation of a precursor (inactive) enzyme be achieved?

A

Through the addition of a cofactor, the action of another enzyme or a change in conditions

52
Q

What is the precursor enzyme called before the addition of the cofactor?

A

An apoenzyme

53
Q

What is a holoenzyme?

A

An enzyme that has been activated by the addition of a cofactor

54
Q

What is a proenzyme?

A

Enzymes that were activated by a change in conditions (e.g. pH or temperature)

55
Q

What is irreversible inhibition?

A

Irreversible inhibitors will bind to an enzyme permanently, so that no other enzyme-substrate complexes can form. It will bind to the enzyme often via a covalent bond

56
Q

What is reversible inhibition?

A

Reversible inhibitors will bind to the active site through hydrogen bonds and weak ionic interactions therefore they do not bind permanently.

Biology Exams (28 decks)

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