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Biology Term 2 > Enzymes > Flashcards

Enzymes Flashcards

1
Q

What type of protein are enzymes?

A

Globular

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2
Q

What are enzymes?

A

Biological Catalysts that increase the rate of a chemical reaction without undergoing permanent change or being used up

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3
Q

Why can enzymes be effective in small amounts?

A

They can be reused repeatedly

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4
Q

How do enzymes speed up reactions?

A

They lower the activation energy

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5
Q

What 3 things must a reaction have in order to take place naturally?

A

1) molecules must collide with sufficient energy to alter the arrangement of their atoms
2) the energies of the reactants/products must be in accordance to if its exo- or endothermic
3) must have achieved its activation energy

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6
Q

What is the activation energy?

A

The minimum amount of energy needed to activate the reaction

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7
Q

Why can metabolic processes occur rapidly at the human body temperature of 37*C (relatively low)?

A

Enzymes allow reactions to take place at lower temperatures by lowering the activation energy

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8
Q

How would our metabolic reactions occur if we didn’t have enzymes?

A

Too slowly to sustain life

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9
Q

What is the enzyme’s specific 3D shape a result of?

A

Their sequence of amino acids (primary protein structure)

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10
Q

What is the functional specific region on the enzyme?

A

The active site

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11
Q

What is the active site made up of?

A

A relatively small number of amino acids.

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12
Q

What does the active site form within the enzyme?

A

A small depression (dip)

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13
Q

What is the molecule which the enzyme acts on?

A

The substrate

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14
Q

What is formed when the molecule fits into the depression?

A

An enzyme-substrate complex

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15
Q

How is the substrate held within the active site?

A

By bonds that temporarily form between certain amino acids of the active site and groups on the substrate molecule

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16
Q

Do amino acids that do not form part of the active site change its shape? (And therefore effect it’s function)

A

Yes - may be one that forms hydrogen bonds with other amino acids, so tertiary structure may be changed - including the active site - so that the substrate may no longer fit.

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17
Q

What is the current model for the function of enzymes?

A

The induced fit model

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18
Q

What does the “induced fit” model propose?

A

The active site forms as the enzyme and substrate interact

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19
Q

How does the proximity of the substrate effect enzyme that forms the functional active site?

A

It leads to a change in the enzyme that forms the active site.

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20
Q

Why can the enzyme mould itself around the substrate?

A

It is flexible

21
Q

How does the strain that is put on the substrate molecule by the enzyme as it’s active site changes shape affect the molecule?

A

Distorts bonds in the substrate and so lowers the activation energy needed to break the bond.

22
Q

Is any change in the enzymes environment likely to change its shape?

A

Yes

23
Q

What is the previous model for enzymes?

A

“Lock and key” model - substrate fits exactly the active site of the enzyme

24
Q

What is the main limitation of the lock and key model?

A

It considered the enzyme to be a rigid structure but it’s structure is flexible

25
Q

What happens if an amino acid within the active site is changed?

A

The changed amino acid may no longer bind to the substrate, which will then not be positioned correctly - or at all - in the active site

26
Q

What two things must happen with an enzyme to ensure it works?

A

1) must have an active site which fits the substrate
2) must come into physical contact with the substrate

27
Q

What 3 things affect the rate of enzyme action?

A

1) pH
2) temperature
3) enzyme concentration

28
Q

What does a rise in temperature increase in the molecules?

A

The kinetic energy

29
Q

How does an increase in temperature affect the rate of enzyme action?

A

It increases it - molecules move around more rapidly and collide more often so the enzymes and substrates come together more often so have more effective collisions so more enzyme-substrate complexes are formed in a given amount of time

30
Q

What does a large rise in temperature cause within the enzyme?

A

Causes the hydrogen and other bonds to break resulting in the enzyme’s active site changing shape

31
Q

What is denaturing?

A

A permanent change that means the enzyme cannot functions again

32
Q

What is the interval in humans from when enzymes begin to denature and are no longer functional?

A

45C - 60C

33
Q

What are 3 advantages to having our body temperature at 37 degrees ( not 40 degrees - optimum )?

A

1) additional energy would be needed to maintain the energy - by food
2) at higher temps other proteins apart from enzymes would be denatured
3) at higher temps any further rise in temperature E.G fever would denature the enzymes

34
Q

Why do different animals have difference normal body temperatures?

A

They have different metabolic rates depending on their lifestyles (E.G birds with flying )

35
Q

What is the pH of a solution?

A

A measure of its hydrogen ion concentration

36
Q

What is an optimum pH?

A

The pH at which an enzyme works fastest

37
Q

What happens if the pH is increased or decreased around the optimum?

A

Rate of enzyme action is decreased

38
Q

What happens if the change in pH is extreme beyond the optimum?

A

The enzyme becomes denatured

39
Q

What pH would a solution with hydrogen ion concentration 1 x10^-9 have?

A

pH 9

40
Q

In terms of amino acids, how does a change in pH affect enzymes?

A

Alters the chargers on the amino acids that make up an active site of an enzyme

41
Q

What happens if the charge on an amino acid within the active site is altered?

A

The substrate can no longer become attached to the active site and so the enzyme-substrate complex can’t be formed

42
Q

How does a change in pH affect an enzyme in terms of its tertiary structure?

A

May cause the bonds maintaining the tertiary structure to break, therefore changing the active site’s shape

43
Q

How does the change in H+ ions result in a change in active site ?

A

Affects the hydrogen and ionic bonds between -NH2 and -COOH groups of the polypeptides that determines the arrangement of the active site

44
Q

Why are enzyme’s activity mostly reduced instead of denatured inside organisms?

A

pH fluctuations are usually small

45
Q

What happens if there is an increase in enzyme concentration?

A
  • as long as there is an excess of substrate - there is a proportional increase in rate of reaction
46
Q

In what case does increasing enzyme concentration have no effect?

A

If there is not sufficient substrate to supply all the enzymes active sites at one time - limiting

47
Q

Why does the graph level off?

A

All the active sites are occupied and the available substrate is already being used

48
Q

Why is there a lower rate of reaction when there is a lower concentration of substrate?

A

The enzymes have only a limited number of substrate molecules to collide with so the active sites are not working at full capacity.

49
Q

Why does the rate of reaction increase when substrate concentration increases m?

A

Active sites are filled to the point where all of them are working as fast as they can

Biology Term 2 (3 decks)

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