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A-Level OCR Biology > Chapter 4 - Enzymes > Flashcards

Chapter 4 - Enzymes Flashcards

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1
Q

What are anabolic reactions?

A

The reactions required for growth

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2
Q

Are all anabolic reactions catalysed by enzymes?

A

Yes

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3
Q

What type of proteins are enzymes?

A

Globular proteins

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4
Q

What are catabolic reactions?

A

The reactions in which molecules are broken down

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5
Q

Are all catabolic reactions catalysed by enzymes?

A

Yes

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6
Q

What is the maximum rate of reaction in enzyme catalysed reactions known as?

A

Vmax

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7
Q

What is required for most reactions to start?

A

Energy (the activation energy)

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8
Q

What is tertiary structure?

A

The overall three-dimensional structure (often as an enzyme)

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9
Q

What is formed after the enzyme-substate complex reacts?

A

The enzyme-product complex

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10
Q

What happens after the enzyme-product complex is formed?

A

The product/s are released, leaving the enzyme unchanged

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11
Q

What is the induced fit hypothesis?

A

The idea that the initial weak interactions between the enz and sub induce changes in the enz tertiary structure slightly
These interactions can weaken bonds in the substrate, lowering the activation energy of the reaction

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12
Q

What are intracellular enzymes?

A

Enzymes that act within the cell that made them

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13
Q

What are extracellular enzymes?

A

Enzymes that work outside the cell that made them

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14
Q

Why are extracellular enzymes needed?

A

Extracellular enzs break down larger molecules that wouldn’t otherwise be able to enter the cell

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15
Q

How do extracellular enzymes function in single-celled organisms?

A

They are released to their immediate environment, and break down nutrients that are then absorbed into the cell

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16
Q

What biological molecule are enzymes made of?

A

Proteins

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17
Q

What is the enzyme involved in step 1 of the digestion of starch?

A

Amylase

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18
Q

What is the enzyme involved in step 2 of the digestion of starch?

A

Maltase

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19
Q

In step 1 of the digestion of starch, what is the starch broken down to?

A

Maltose

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20
Q

In step 2 of the digestion of starch, what is the maltose broken down to?

A

Glucose

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21
Q

What is protease?

A

A type of enzyme that breaks down proteins and peptides

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22
Q

What is trypsin?

A

A protease, that catalyses the digestion of proteins into smaller peptides, which can then be broken down further into amino acids by other proteases

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23
Q

Where is trypsin produced?

A

In the pancreas

24
Q

What is the temperature co-efficient/Q10 of a reaction?

A

How much the rate of reaction increases with a 10 degrees Celsius temperature increase

25
Q

How does temperature cause the denature of enzymes?

A

As the temperature increases, the enzyme vibrates more and more until the enzymes bonds strain and break. This changes the tertiary structure of the enzyme

26
Q

At what point does the temperature co-efficient in an enzyme controlled reaction not apply?

A

Once it has denatured

27
Q

How does pH cause the denature of enzymes?

A
  • The active site will only be the right shape at a certain H+ ion concentration
  • Therefore if the pH/H+ concentration is too high or low, the enzyme will denature
28
Q

What is renaturation?

A

When pH only moderately goes beyond the optimum, the enz will denature, however if the pH returns to the optimum, the correct enz shape will return

29
Q

Can renaturation always occur in pH changes and why?

A

No, if the pH becomes to extremely changed beyond the optimum, the active site can be permanently changed

30
Q

How do competitive inhibitors slow rate of reaction?

A

They block substrates from entering the active site of the enzyme

31
Q

Does competitive inhibition lower the vmax of the enzyme it inhibits?

A

No, it will just slow the rate it reaches it

32
Q

Where do non-competitive inhibitors bind?

A

The allosteric site of the enzyme

33
Q

How do non-competitive inhibitors slow rate of reaction?

A

They change the tertiary structure of the enzyme, meaning the substrate is no longer complimentary to the active site

34
Q

Can enzymes reach their vmax in the fixed presence of non-competitive inhibitors?

A

No

35
Q

What is end-product inhibition?

A
  • When the end product of a reaction acts as an inhibitor to the enzyme that produced it
  • Serves as negative feedback control for the reaction
36
Q

What is the purpose of end-product inhibition?

A

So that excess products aren’t made and resources aren’t wasted

37
Q

Give an example of end-product inhibition

A
  • In respiration, when ATP levels are high, more ATP binds to the allosteric site on PFK, non-competitively inhibiting ATP production
  • As ATP is used up, the amount of inhibiting ATP lessens, so more ATP is produced
38
Q

What are co-factors/enzymes?

A

Non-protein enzyme helpers

39
Q

What is the difference between co-factors and co-enzymes?

A

Co-enzymes are organic, co-factors are inorganic

40
Q

What is the main example of cofactors?

A

Cl- in amylase

41
Q

What is the main example of coenzymes?

A

NAD (in respiration) and A (in respiration)

42
Q

Are cofactors/coenzymes permanent features?

A

No, they are only temporary

43
Q

What are prosthetic groups?

A

Enzyme helpers

44
Q

What makes prosthetic groups different to cofactors/enzymes?

A

They form a permanent feature on the protein

45
Q

What is the main example of prosthetic groups?

A

Zn2+ in carbonic anhydrase

46
Q

What are inactive precursor enzymes?

A

Enzymes that are produced with the incorrect tertiary structure so are in an inactive form

47
Q

How do precursor enzymes become active?

A

They must undergo a change in tertiary structure, which can be achieved by adding a cofactor

48
Q

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

A

An apoenzyme

49
Q

What is a holoenzyme?

A

An enzyme that has received a cofactor and is now active

50
Q

What are proenzymes?

A

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

51
Q

What is another name for proenzymes?

A

Zymogens

52
Q

In competitive inhibition, if the substrate concentration is increased enough, what is the effect and why?

A

The Vmax can still be reached, as there will be so much more substrate than inhibitor

53
Q

In non-competitive inhibition, what is the effect of adding more substrates?

A

Adding more substrates will not overcome the effect of the non-competitive inhibitors, meaning Vmax cannot be reached

54
Q

In non-competitive inhibition, what is the effect of adding more non-competitive inhibitors?

A

The rate of reaction and the maximum rate of reaction will decline further

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.

57
Q

How do co-enzymes bind to enzymes?

A

Loosely

A-Level OCR Biology (21 decks)

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