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AQA A level Biology > 1.4.2 Enzymes > Flashcards

1.4.2 Enzymes Flashcards

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1
Q

Enzymes are described as biological catalyst, what does this mean

A

Biological- means produced by living tissue
Catalyst- means speeds up the rate of reaction and they don’t get changed by the reaction

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2
Q

What is a catabolic enzyme

A

An enzyme that breaks down large molecules into smaller ones

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3
Q

What is an anabolic enzyme

A

An enzyme that builds up smaller molecules into larger molecules

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4
Q

What type of protein is an enzyme

A

Globular protein

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5
Q

Enzymes don’t cause reactions to happen, instead they do what to reaction

A

They speed up reactions that were already taking place

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6
Q

What is the name of the specific region of the enzymes

A

The active site

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7
Q

Is the enzymes’ active site made from many or few amino acids

A

Relatively few amino acids

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8
Q

What is the name given to the molecule that the active site acts upon

A

Substrate

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9
Q

What is formed when an enzyme and substrate fit neatly

A

An enzyme-substrate complex

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10
Q

The enzyme is ——- to the substrate (fill in blank)

A

Complementary

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11
Q

What are the 2 locations of enzyme action

A
  • Intracellular
  • Extracellular
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12
Q

In intracellular enzyme action, what are the 3 organelles in which enzymes are located

A
  • Lysosomes
  • Cytoplasm
  • Mitochondrial membrane
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13
Q

In extracellular enzyme action, what is the main system in which enzymes action occurs

A

Digestive system, alimentary canal

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14
Q

What is an exergonic reaction

A

A reaction which releases energy

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15
Q

What is an endergonic reaction

A

A reaction which requires energy

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16
Q

How do enzymes catalyse a reaction

A

By lowering the activation energy

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17
Q

Name the 2 enzyme action theories

A
  • Lock and key mechanism
  • Induced fit
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18
Q

What forms when a substrate binds to an enzyme

A

Enzyme-substrate complex

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19
Q

A substrate bust be complementary in —— to the active site (fill in the blank)

A

In shape

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20
Q

How does the induced fit model describe the active site

A

That it’s not quite complementary in shape but then moulds to the shape of the substrate

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21
Q

In the induced fit model, what happens to the active site once the products are released

A

They go back to their original shape, so they’re unaltered by the reaction

22
Q

True or false: enzymes are generally large complex fibrous proteins

A

False, they are globular

23
Q

True or false: the active site forms only a small part of the whole enzyme and is highly specific for its substrate

A

True

24
Q

True or false: Enzymes increase the rate of reaction by lowering the activation energy of the reaction

A

True

25
Q

True or false: The formation of an enzyme-substrate complex makes the substrate more stable

A

True

26
Q

True or false: In the induced fit model, the enzyme and its active site change shape when the substrate binds

A

True

27
Q

True or false: Enzymes can catalyse reactions that would not otherwise occur

A

False

28
Q

True or false: Anabolic reactions involve the break down of large substrates into smaller ones

A

False, catabolic reactions break down, anabolic build up

29
Q

True of false: Endergonic reactions require an intake of energy

A

True

30
Q

True or false: ATP hydrolysis is an endergonic reaction

A

False, its an exergonic reaction

31
Q

True or false: Enzyme action in the alimentary canal is an example of intracellular digestion

A

False, its an example of extracellular

32
Q

What is the equation to calculate rate when the dependent variable is time

A

1/ Time (in seconds)

33
Q

What is the unit for rate of reaction when the dependent variable is time (2 answers)

A

s ^-1
s^-1 x 10^-3

34
Q

What is the calculation for rate of reaction when the dependent variable is mass or volume

A

Volume/ time (in seconds)
Mass/ time (in seconds)

35
Q

What are the 4 factors that affect enzyme action

A
  • Temperature
  • pH
  • Substrate concentration
  • Enzyme concentration
36
Q

On a rate of reaction against temperature on an enzyme action graph, why does the graph initially increase

A

Because there is an increase in kinetic energy of both enzymes and substrates so there is an increase of successful collisions so there is an increase in enzyme-substrate complexes formed so there is more product formed in a certain period of time

37
Q

On a rate of reaction against temperature on an enzyme action graph what does the peak of the graph mean

A

The optimum temperature

38
Q

On a rate of reaction against temperature on an enzyme action graph why does the graph decrease after the peak

A

Because the amino acids which make up the protein begin to vibrate so the hydrogen bonds between the R groups begin to break so the tertiary structure of the enzyme changes shape which in turn alters the shape of the active site- denaturing the enzyme so the substrate is no longer complementary so fewer enzyme-substrate complexes form so fewer products are produced per period of time

39
Q

In extreme pH what type of bonds in the enzyme are broken

A

Ionic bonds

40
Q

What is an enzyme inhibitor

A

A molecule that interferes with/ slows down enzyme activity

41
Q

What are the 2 types of enzyme inhibitors

A
  • Competitive
  • Non- competitive
42
Q

Can maximum rate of reaction still be achieved when a competitive inhibitor is present

A

Yes, when you increase the substrate concentration

43
Q

How does a competitive inhibitor work

A

By binding to the active site so fewer enzyme-substrate complexes form per unit of time

44
Q

How does a non-competitive inhibitor work

A

It binds somewhere other than the active site, known as the allosteric site, which changes the tertiary structure, so changes the shape of the active site preventing substrate from binding, fewer enzyme-substrate complexes form

45
Q

What is a metabolic pathway

A

A series of reactions in which each step is catalysed by an enzyme

46
Q

Describe the induced-fit model of enzyme action and how an enzyme acts as a catalyst (3 marks)

A
  • Substrate binds to the active site
  • Active site changes shape slightly so it is complementary to substrate
  • Reduces activation energy
47
Q

A competitive inhibitor decrease the rate of an enzyme-controlled reaction. Explain how. (3 marks)

A
  • Inhibitor similar shape to substrate / complementary to active site
  • Binds to active site
  • Reduces enzyme-substrate complex forming
48
Q

Explain how the active site of an enzyme causes a high rate of reaction (3 marks)

A
  • Lowers activation energy
  • Induced fit causes the active site to change shape
  • So enzyme-substrate complex causes bonds to form/break
49
Q

Describe how a non-competitive inhibitor can reduce the rate of an enzyme-controlled reaction (3 marks)

A
  • Attaches to the enzyme at a site other than the active site
  • Changes shape of the active site
  • So active site and substrate no longer complementary so less substrate can bind
50
Q

Formation of an enzyme-substrate complex increases the rate of reaction. Explain how. (2 marks)

A
  • Reduces activation energy
  • Due to bending bonds / without enzyme, very few substrates have sufficient energy for reaction

AQA A level Biology (35 decks)

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