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Medical Biochemistry > Enzymes > Flashcards

Enzymes Flashcards

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USMLE® Step 1 flashcards
1
Q

What is a ribozyme?

A

An RNA molecule that can catalyze a biochemical reaction

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2
Q

What is an Abzyme?

A

A product produced in the lab by attaching an antibody to the active site structure isolated from an enzyme

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3
Q

What’re the two models for enzyme structure and function?

A
  • Lock/Key

- Induced Fit

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4
Q

What nonprotein components are essential for enzyme activity?

A
  1. Prosthetic groups: Nonroteiin organic structures tightly bound to enzyme ex. Heme in cytochrome C
  2. Coenzymes: Less tightly bound substance frequently derived from vitamins
  3. Cofactors: Metal ions or simple organic molecules
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5
Q

What are the classifications of enzymes?

A
  • Oxidoreductase
  • Tranferase
  • Hyrdolase
  • Lyase
  • Isomerase
  • Ligase
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6
Q

What type of reaction is catalyzed by an Oxidoreductase?

A

Redox rxns (Addition/removal of e-)

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7
Q

What type of reaction is catalyzed by a Tranferase?

A

Transfer of a specific group (phosphorylation, etc)

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8
Q

What type of reaction is catalyzed by a Hydrolase?

A

Bond breakage via H20

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9
Q

What type of reaction is catalyzed by a Lyase?

A

Bond breakage w/h out water

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10
Q

What type of reaction is catalyzed by an Isomerase?

A

Formation of an Isomer (ex group switching trans/cis)

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11
Q

What type of reaction is catalyzed by a Ligase?

A

Bond formation (ex carboxylation)

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12
Q

How does pH affect pH?

A
  • Enzymes operate optimally about some particular pH. Activity drops off in a bell shaped curve around that pH
  • Due to chaired groups at active sites or salt bridges =becoming titrated
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13
Q

Ho does temperature affect enzyme activity?

A
  • there is an optimal temperature for enzyme activity

- Temperature increases kinetic activity until a certain point at which the protein starts to denature

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14
Q

What are isozymes?

A

Enzymes from the same species which have the same activity, but differ in chemical structure and kinetic properties

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15
Q

Heat is the Michealis-menton equation?

A

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

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16
Q

What is the reaction velocity at very low [S]?

A

V = Vmax[S] / Km

17
Q

What is the reaction velocity at very high [S]?

A

V = Vmax

18
Q

How does enzyme concentration affect Km?

A

It doesn’t

19
Q

How is enzyme Km related to binding affinity?

A

Smaller Km, Higher affinity

20
Q

How are reaction rates related to dissociation contants?

A
  • When K2<
21
Q

What is the line weaver-Burk equation?

What is the slope?

What is it’s usefulness in medicine?

A

1/V = Km/Vmax x 1/[S] x 1/Vmax

Slope = Vmax

Used to identify inhibitors

22
Q

What is the equation for the Eddie-Hofstra plot?

A

V = {-Km(V)} / [S]

23
Q

What are the two types of inhibitors, and how do they affect Km and Vmax?

A

Irreversible: Removes some enzyme from reaction mixture; only affects Vmax

Reversible: Can affect either or both Km or Vmax

24
Q

What is an example of beneficial irreversible inhibition?

A

Penicillin for inhibiting glycopeptuide transpeptidase in staph. Aureus

25
Q

What are the three types of reversible inhibitors?

A
  1. Competitive
  2. Uncompetitive
  3. Noncompetitive
26
Q

What is an example of competitive inhibition?

A

Rate-limiting step for Cholesterol biosynthesis

Reduction of 3 hydroxymethylglutaryl Coa to Mevalonate and CoAsh

27
Q

What is an example of noncompetitive inhibitors?

A

Lead poisoning causing anemia

28
Q

What is an example of uncompetitive inhibitors?

A

Lithium inhibition of Inositol phosphatase

Manic depression

29
Q

How are allosteric enzyme regulated?

A
  • Either inhibited or activated by effectors binding to a site other than the active site
30
Q

What are the states of an allosteric enzyme?

A

R State - More Active (relaxed)

T State - Less active (Taut)

31
Q

What is an example of allosteric regulation?

A

Regulation of aspartame transcarboxylase to produce N-Carbamoyl Aspartate

32
Q

How is K calculated for Allosteric enzymes?

A

K = [S]^n x [Vmax - V] / V

33
Q

When is a lineweaver Burke plot linear for an allosteric enzyme?

A

When n = 1

Medical Biochemistry (26 decks)

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