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1. Biochemistry > Enzymes > Flashcards

Enzymes Flashcards

1
Q

What type of protein are most enzymes?

A

Globular proteins

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2
Q

Most enzymes are globular proteins, what characteristics do they have because of this?

A

Because of this enzymes are mostly spherical and water soluble

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3
Q

Why are enzymes water soluble?

A

They have to exist in the cell which has an aqueous environment

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4
Q

What do most enzymes do?

A

They make reactions happen quicker i.e. they make biological reactions happen at a rate that sustains life

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5
Q

Give three examples of different types of enzymes.

A

Abzymes
Ribozymes
DNAzymes

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6
Q

What do abzymes do?

A

They speed up reactions of the immune system

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7
Q

What do enzymes act on?

A

Other molecules/substances

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8
Q

After a long period of time and many uses, what will happen to an enzyme?

A

They will wear out and eventually degrade

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9
Q

What is the molecule that an enzyme acts on called?

A

The substrate

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10
Q

What is an active site?

A

The area on an enzyme where a reaction occurs

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11
Q

What happens at the active site?

A

There is a moving around of electrons and the forming/breaking of bonds

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12
Q

What is formed when the substrate binds to the active site of the enzyme?

A

The enzyme/substrate complex is formed

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13
Q

What is formed after the enzyme/substrate complex?

A

The enzyme/product complex is formed

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14
Q

What happens after the enzyme/product complex is formed?

A

The products leave the active site of the enzyme

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15
Q

What is the most common type of reaction that occurs to form products?

A

The substrate is split to form products

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16
Q

Describe the relationship between chemical reactions and enzyme reactions.

A

Enzyme reactions are a specialised type of chemical reaction

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17
Q

List four characteristics of a chemical reaction

A

Reactants converted into products

May involve catalyst

Rate of reaction can be measured

Rate increases as temperature increases without a limit

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18
Q

List four characteristics of an enzyme reaction

A

Substrates converted into products

Always involve catalyst (enzyme)

Rate of reaction can be measured

Rate increases as temperature increases up to a limit

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19
Q

What happens to enzymes when a certain high temperature is reached?

A

Denaturation occurs

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20
Q

What happens when an enzyme is denatured?

A

The active site is lost, there is nowhere for the substrate to bind to -> the reaction cannot occur

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21
Q

Give the name of one of the fastest enzymes.

A

DNase

22
Q

What does it mean if a word end with ‘ase’?

A

The ending ‘ase’ indicates an enzyme

23
Q

What type of molecule are protein enzymes?

A

They are polypeptides

24
Q

What are polypeptides?

A

They are long chains of different amino acids

25
Q

Describe the structure of a polypeptide.

3

A

Chain is folded to achieve a specific overall shape

Usually looks like a bumpy globe (globular)

Surface features based on the different amino acids (side chains)

26
Q

What happens if an enzyme is not folded correctly?

A

The active site will not be in the correct place, the reaction cannot occur

27
Q

What happens if a substrate doesn’t fit in an active site?

A

The reaction will not happen

28
Q

Describe the structure of the active site.

4

A

It has a 3D conformation

Amino acids protrude from the surface

There is a specific arrangement

Amino acids are often charged

29
Q

What keeps the substrate in the active site?

A

Reactions such as those between oppositely charged areas of the substrate and the active site

30
Q

What is needed for an enzyme/substrate reaction to occur?

3

A

Large amounts of the substrate - the more substrate the greater the chance one will come in contact with the activation site

Activation energy (Ea) - the energy needed for the reaction to start

An enzyme needed to bend the substrate into a shape so the reaction occurs more quickly

31
Q

What is activation energy?

A

The minimum amount of energy needed for a reaction to start

32
Q

Give an example of one form of activation energy.

A

It can come in the form of ATP

33
Q

How exactly do enzymes increase the rate of reaction?

2

A

They do this by slightly changing the conformation/shape of the substrate so that its more like the product

This allows the reaction to occur more easily and therefore increases the rate of reaction

34
Q

What would happen if the substrate 100% rigid and unyielding?

A

The reaction would not occur

35
Q

What is enzyme kinetics?

A

Measuring the rates of reaction of enzymes

36
Q

Give two ways we know catalysts do anything.

A

An increase in product formation

A decrease in amount of substrate

37
Q

How do we study enzyme kinetics?

2

A

By using a substrate that is practical and convenient to monitor i.e. it is highly coloured or fluorescent, radioactive etc

We can then use a spectrophotometer to monitor the reaction

38
Q

Why does the amount of free enzyme decrease?

A

It decreases as the enzyme/substrate complex is made -> the ES complex increases

39
Q

What happens as the amount of substrate decreases?

A

The amount of product increases

40
Q

What does the Michaelis-Menten Equation allow us to do?

A

It allows us to calculate the expected velocity at a given [S] as we have established the Vmax and Km for an enzyme/substrate reaction pair

41
Q

What is the Michaelis-Menten Equation?

A

Velocity = Vmax [S]/Km + [S]

42
Q

What is the common rule of thumb for the relationship between temperature and rate of reaction?

A

That a 10 degrees increase in temperature doubles the rate of reaction
(this only happens up to a certain point for enzyme reactions)

43
Q

What is actually happening in enzyme inhibition?

A

The enzyme cannot complete a catalytic cycle

44
Q

What is formed in enzyme inhibition?

A

An enzyme inhibitor complex is formed (EI complex)

45
Q

What are the two forms of an EI complex?

A

Reversible of irreversible

two types of inhibition

46
Q

What happens in reversible inhibition?

3

A

The inhibitor can bind to and dissociate from the enzyme

Activity is lost when the inhibitor is bound

Must wait for the enzyme to become free to overcome this inhibition

47
Q

What happens in irreversible inhibition?

2

A

The enzyme is covalently modified and the activity is lost

Must replace the enzyme to overcome this inhibition

48
Q

What are the three forms of reversible inhibition?

A

Competitive

Uncompetitive

Mixed

49
Q

What happens in competitive inhibition?

2

A

The inhibitor binds at the active site

This prevents the substrate from binding

50
Q

What happens in uncompetitive inhibition?

2

A

The inhibitor bind to the enzyme-substrate complex

This does not happen at the active site

51
Q

What happens in mixed inhibition?

A

The inhibitor can bind to the free enzyme of the enzyme substrate complex

52
Q

How does pH influence enzyme activity?

A

By altering amino acid structure - particularly those in the active site

1. Biochemistry (6 decks)

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