Brar - Enzymes, Enzyme Kinetics Flashcards

1
Q

What do and don’t enzymes do?

A

Catalyze specific biochemical reactions

DO NOT create new reactions.

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2
Q

List 4 general areas where enzymes are needed as catalysts.

A

Mitochondrion, cytosolic, lysosomal, and nuclear areas.

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3
Q

How do enzymes catalyze reactions?

A

They are specific and reduce the activation energy required for the reaction to occur.

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4
Q

Can enzymes be used more than once?

A

Yes, they are not destroyed and return to their original state after rxn.

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5
Q

What occurs in an enzyme’s active site?

A

an enzyme-substrate complex is formed and the site contains functional groups that help in rxns

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6
Q

What are the 2 substrate binding models?

A

Lock and key model

Induced fit model

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7
Q

Describe the Lock and key model.

A

fixed and rigid model; small differences in structure can prevent proper binding

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8
Q

Describe the Induced Fit model.

A

flexible 3-D structure that undergoes conformational change when substrate binds and exposes more residues.

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9
Q

What is the transition state complex?

A

maximum energy level reached during a rxn; it is unstable and decomposes to products

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10
Q

What is activation energy?

A

the difference in energy between the substrate and the transition state complex

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11
Q

Which amino acid is one of the more important functional groups of an active site?

A

Serine-OH in proteases

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12
Q

What effects does pH have on enzyme catalysis?

A

it can denature the enzyme, decrease its function the farther away from it’s ideal pH level, or change its function based on the pH level

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13
Q

What are 2 mechanism based inhibitors?

A

Covalent inhibitors and Transition State Analogs

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14
Q

How do covalent inhibitors work?

A

covalently bind to residues in active site and renders enzyme useless or dead

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15
Q

Is a covalent inhibition reversible?

A

No, it is irreversible.

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16
Q

List some examples of covalent inhibitors? What enzyme do they inhibit?

A

Sarin, malathion, and parathion (pesticides).

Acetylcholinesterase

17
Q

What are transition state analogs?

A

Irreversible inhibitors sometimes termed “suicide inhibitors” that reduce/eliminate an enzyme’s function

18
Q

List some examples of transition state analogs and the enzymes they inhibit.

A

Penicillin → Glycopeptidyl transferase (GPT)

Allopurinol → Xanthine oxidase

19
Q

What is Allopurinol used to treat?

A

Gout by decreasing urate porduction

20
Q

What enzymatic reactions do Oxidoreductases catalyze?

A

Oxidation-reduction reactions.

Lactate ↔ Pyruvate (Lactate dehydrogenase)

21
Q

What do Transferases catalyze?

A

transfer of C-, N-, or P- containing groups.

Serine ↔ Glycine (Serine hydroxy-methyl transferase

22
Q

What do Hydrolases catalyze?

A

cleavage of bonds by adding H20.

Urea → CO2 + 2 NH3 (Urease)

23
Q

What do Lyases catalyze?

A

cleavage of C-C, C-S, and certain C-N bonds.

Pyruvate → Acetaldehyde (Pyruvate decarboxylase)

24
Q

What do Isomerases catalyze?

A

racemization of optical or geometric isomers.

Methylmalonyl CoA ↔ Succinyl CoA (Methylmalonyl CoA mutase)

25
Q

What do Ligases catalyze?

A

formation of bonds btwn C and O, S, or N coupled to hydrolysis of high energy phosphates.
Pyruvate → Oxaloacetate (Pyruvate carboxylase)

26
Q

As substrate concentration increases, what else increases?

A

the velocity (V) of the reaction

27
Q

How much or how long will the velocity increase?

A

until the enzyme is saturated; this point is known as Vmax

28
Q

What is Km and what is it also known as?

A

the minimum substrate concentration required for effective catalysis to occur; Michaelis Menten constant

29
Q

What two parts of the reaction below determine the rate of reaction?
k1 k2
E + S ↔ ES → E + P
k-1

A

concentration of ES and k2

30
Q

Name the following equation
k2[ET][S]
V = —————
Km + [S]

A

the Michaelis Menten (MM) equation

31
Q

What is the Km value a reflection of?

A

an enzymes affinity for its substrate; low Km = high affinity

32
Q

If the Km value is high, what does that mean?

A

the enzyme has a low affinity for its substrate therefore a higher substrate concentration is needed

33
Q

What does the turnover number (kcat) measure?

A

it directly measures the rate of the catalytic process and it is used instead of k2 in multi-step rxns

34
Q

What can the kcat value also be thought as?

A

a frequency

35
Q

What does the ratio of kcat/Km measure?

A

it conveniently measures enzyme efficiency

36
Q

What is the most efficient enzyme in the world?

A

Carbonic Anhydrase

37
Q

What factors affect the reaction velocity?

A

Substrate concentration, temperature, and pH

38
Q

What does Michaelis Menten enzyme and allosteric enzyme activity look like on a graph?

A

MM enzymes follow a hyperbolic curve

Allosteric enzymes follow a sigmoid curve

39
Q

hat is the optimum temperature for most human enzymes?

A

35 - 40 degrees celcius