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Biochemistry > Enzymes > Flashcards

Enzymes Flashcards

1
Q

What is phenylalanine hydroxylase?

A

catalyzes the conversion of Phe to Tyr

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2
Q

What are enzymes?

A
  • structurally specific but dynamic
  • typically globular proteins with degree of flexibility
  • mostly proteins
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3
Q

What enzyme has the highest rate enhancement?

A

OMP decarboxylase

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4
Q

What is a substrate?

A

substance acted on by an enzyme

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5
Q

What is an active site?

A

groove on an enzyme where substrate binds and undergoes reaction

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6
Q

What are the 4 characteristics of enzymes?

A
  1. do not make reaction occur that could occur on its own
  2. not permanently altered by the reaction
  3. can catalyze both forward and reverse reaction
  4. highly specific
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7
Q

Do enzymes increase or decrease activation energy?

A

decrease

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8
Q

Do enzymes affect the equilibrium or Gibbs free energy of a reaction?

A

no

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9
Q

What is the lock and key model?

A

active site of unbound enzyme is complementary in shape to substrate

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10
Q

What is the Gibbs free energy equation?

A

G0= -2.303 RT log Keq

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11
Q

What is the induced fit model?

A

active site changes shape on substrate binding after the substrate has been bound

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12
Q

Which enzyme model decreases activation energy? Which increases?

A
  • decreases: induced fit
  • increases: lock and key
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13
Q

What are the 4 mechanisms that enzymes use?

A
  1. proximity effect
  2. orientation effect
  3. promotion of acid-base reactions
  4. water exclusions
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14
Q

What is the proximity effect?

A

active site brings reactants closer together to increase rate of reaction

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15
Q

What is the orientation effect?

A

active site orients the reactants to increase rate of reaction

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16
Q

What is the promotion of acid-base reacgtions?

A

active site donate/accept proton to weaken covalent bonds

17
Q

What is the exclusion of H2O?

A

active sites being hydrophobic to lower activation energy

18
Q

Where does the specificity of trypsin occur?

A

cleaves on carboxyl side of Lys (K) or Arg (R)

19
Q

Where does the specificity of chymotrypsin occur?

A

cleaves on carboxyl side of aromatic (F, Y, W) or large hydrophobic amino acids

20
Q

What is the catalytic triad?

A

His, Asp, Ser

21
Q

What happens to serine in the catalytic triad?

A

becomes a strong nucleophile due to being close to His which is close to Asp

22
Q

Why does cysteine protease become an important residue?

A

involved in breakage of peptide bond

23
Q

What is the role of aspartic protease?

A

aspartic amino acids activate water molecule

24
Q

What makes up a holoenzyme (active enzyme)?

A

apoenzyme + cofactor

25
Q

What makes a cofactor?

A

metal ions + organic or metallorganic molecules

26
Q

What are examples of important coenzymes?

A
  • vit B2 (flavins)
  • vit B3 (niacin)
  • vit B5 (pantothenic acid)
  • vit B7 (biotin)
  • vit B1 (thiamine pyrophosphate)
  • vit B6 (pyridoxal phosphate)
27
Q

What are the 6 major classes of enzymes?

A
  1. oxidoreductases -> oxidation/reduction
  2. transferases -> group transfer
  3. hydrolases -> hydrolysis reactions
  4. lyases -> addition/removal of group to form double bonds
  5. isomerases ->isomerization of 2 substrates
  6. ligases -> ligation of 2 substrates with ATP hydrolysis
28
Q

What is a proenzyme/zymogen?

A

the inactive precursor of an enzyme converted into an active enzyme by proteolysis

29
Q

What is an example of irreverisble reaction?

A

the conversion of proenzymes inot an active enzyme

30
Q

What are isoenzymes?

A

enzymes that differ in amino acid sequence but catalyze the same chemical reaction

31
Q

What can isoenzymes do?

A
  • be tissue specific
  • play important regulatory roles
  • be used as biomarkers
32
Q

What enzyme can be used as a biomarker for a heart attack?

A

lactate dehydrogenase

Biochemistry (20 decks)

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