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MD2001 Week 4 > Introduction to Enzymes > Flashcards

Introduction to Enzymes Flashcards

1
Q

What are enzymes?

A

Biological catalysts

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2
Q

How do enzymes work?

A

By lowering the activation energy required for a chemical reaction by stabilising the transition state

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3
Q

What is rate enhancement calculated by?

A

Catalysed rate/uncatalyzed rate

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4
Q

What is the clinical importance of enzymes?

A

Looking at specific diseases

Using them for diagnosis

Looking at drug therapy

Basic research

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5
Q

If the substrate concentration increases, what also increases?

A

Reaction velocity

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6
Q

How dower measure enzyme activity?

A

Measured by increasing the substrate concentration and measuring the accumulation of products over time

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7
Q

What is enzyme activity dependent on?

A

How rapidly it can process a substrate

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8
Q

What is the maximum velocity a reaction can go to? denoted by?

A

Vmax

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9
Q

How do we gain more information about the activity of an enzyme?

A

Using Lineweaver-Burke plot

Putting [S} and Vo under 1

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10
Q

What is Km?

A

Used along with Vmax to measure enzyme activity

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11
Q

What does Km equal?

A

The substrate concentration that is required to reach half of maximum velocity

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12
Q

What is the usefulness of a lower Km?

A

Can work in lower concentration

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13
Q

How do we measure Km?

A

-1/Km is equal to the x intercept

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14
Q

What are enzymes inhibitors?

A

Chemicals that interfere with enzyme reactions

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15
Q

What are the two types of enzyme inhibitors?

A

Irreversible or reversible

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16
Q

What are irreversible inhibitors?

A

They react with the enzyme and form a covalent bond adduct with the protein

17
Q

What is the main function of diisopropyl fluorophosphate and what inhibition does it use? (DIPF)

A

Inhibition of acetylcholinesterase

Irreversible

18
Q

What is AChE?

A

An enzyme that degrades the neurotransmitter acetylcholine into choline and acetic acid

19
Q

What classification does DIPF come under?

A

Organophosphates

20
Q

Describe the inhibition by aspirin?

A

Irreversible

  • Aspirin acetylates the alpha-amino group of the terminal serine of the enzyme forming a covalent bond
21
Q

What competitive inhibition?

A

Where a drug will compete with the substrate for the active site of the enzyme

22
Q

How do competitive inhibitor alter the kinetics of an enzyme?

A

You can achieve Vmax but will require more substrate ie Km

23
Q

What is allosteric inhibition?

A

Bind to another area of the enzyme, changing the structure and stopping the substrate binding in the active site

24
Q

What is graphical effect of allosteric inhibition?

A

Vmax decreases

Km often (but not always) increases

25
Q

What are the two types of allosteric inhibition?

A

Mixed and non-competitive

26
Q

What is the graphical effect of mixed allosteric inhibition?

A

Vmax decreases due to inhibtion

Km increases as substrate affinity is reduced

27
Q

What is the graphical effect of non-competitive inhibition?

A

Vmax decreases due to reduced efficiency of the reaction

Km is unchanged

28
Q

Example of allosteric inhibition

A

Phosphofructokinase is inhibited when ATP has high levels due to it having two binding sites, one active and one inhibiting

29
Q

Example of competitive inhibition

A

Sulphonamides starve bacteria of essential folic acid by occupying the enzymes that would be binding to 4-aminobenzoic acid as they have a similar structure

30
Q

Why is anti-freeze poisonous?

A

It is converted from ethylene glycol into oxalate by alcohol dehydrogenase

31
Q

How do we treat anti-freeze poison?

A

Inducing a near-fatal dose of ethanol

Ethanol then competes with ethylene glycol for alcohol dehydrogenase so slows down reaction

MD2001 Week 4 (10 decks)

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