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biochem midterm > Enzymes - w3 > Flashcards

Enzymes - w3 Flashcards

1
Q

What is the job of enzymes?

A

lowers the activation energy (but doesn’t change net energy for the reaction)

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2
Q

What are the four catalytic strategies of enzymes?

A

proximity and orientation of substrates, metal ions, acid-base catalysis, covalent catalysis

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3
Q

Which catalytic strategy acts as electron-attaching groups?

A

metal ions (zinc and acetaldehyde)

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4
Q

Which catalytic strategy has active sites that may contain residues which can cause hydrogen ion transfer?

A

histidine, chymotrypsin

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5
Q

What is the optimum temperature for most human enzymes?

A

35-40 C

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6
Q

What is the optimum pH for enzymes?

A

varies depending on the enzyme

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7
Q

What is the clinical way to classify enzymes?

A

systematic naming system and four-digit classification number

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8
Q

What are the two main types of cofactors?

A

inorganic (metal ions) and organic/co-enzymes (vitamins)

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9
Q

What is the lock and key model type of binding?

A

complementarity between enzyme and substrate by hydrogen bonds or electrostatic interactions

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10
Q

What is the induced-fit model of bonding?

A

binding induces conformational change in the active site

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11
Q

What do we call the intermediate change at binding, and has unstable high-energy?

A

transition state complex

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12
Q

Which type of enzymes catalyzes redox reactions?

A

oxidoreductase

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13
Q

Which type of enzymes catalyzes the transfer of C, N, or P-containing groups?

A

transferase

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14
Q

Which type of enzymes catalyzes the cleavage of bonds by the addition of water (+ H20 ->)

A

hydrolase

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15
Q

What type of enzymes catalyzes the SPLITTING of C-C,S,N bonds?

A

lyase/synthase (decarboxylase)

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16
Q

What type of enzymes catalyzes the rearrangement of optical or geometric isomers?

A

isomerase

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17
Q

What type of enzymes catalyzes the FORMATION of bonds between carbon to O,S,N using ATP?

A

ligase

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18
Q

What does the rate of formation of the substrate dependent on?

A

the concentration of the substrate

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19
Q

What is the constant concentration of the enzyme-substrate (ES)?

A

steady-state concentration

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20
Q

What is the rate-limiting step of enzyme kinetics?

A

decomposition of the ES complex into E + P

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21
Q

What is the Km formula?

A

[E] [S] / [ES]

22
Q

Why is Km a first order reaction when [S] is lower than Km?

A

the V (velocity) of the reaction is proportional to the substrate concentration

23
Q

What do we call the straight line obtained if 1/Vo is plotted against 1/[S]?

A

Lineweaver-Burk plot (Km/Vmax)

24
Q

What is the use of the Lineweaver-Burk plot?

A

to determine the mechanism of action of enzyme inhibitors

25
Q

What are the two reversible enzyme inhibitors?

A

competitive and noncompetitive

26
Q

What is enzyme competitive inhibition?

A

inhibitor binds to the SAME site as the substrate (analogue)

27
Q

How can we reverse the effect of competitive inhibition?

A

increasing substrate concentration

28
Q

How does competitive inhibition affect enzyme kinetics?

A

increases Km, but doesn’t affect Vmax

29
Q

What is the enzyme in the liver that methanol (bad) and ethanol (good) compete for?

A

alcohol dehydrogenase

30
Q

What is enzyme non-competitive inhibition?

A

inhibitor binds to a different site on the enzyme and doesn’t interfere with substrate binding?

31
Q

How does non-competitive inhibition affect enzyme kinetics?

A

Km remains unchanged, Vmax is reduced

32
Q

What is the inhibitor of angiotensin converting enzyme, reducing high blood pressure?

A

captopril

33
Q

What are the three irreversible enzyme inhibitors?

A

covalent/suicide inhibitors / transition state analogues / heavy metal toxicity

34
Q

What do covalent/suicide inhibitors do?

A

form strong bonds with functional groups in the catalytic active site

35
Q

What type of compounds cause acetylcholinesterase inhibition?

A

organophosphorus compounds (malathion)

36
Q

What do transition state analogues do?

A

tightly binds to the active site, mimicking the transition state -> inhibiting the enzyme from binding to its normal substrate

37
Q

How does penicillin act as a transition state analogue?

A

it inhibits bacterial enzyme from crosslinking the bacterial cell wall peptidoglycan strands

38
Q

What is the transition state analogue part of penicilin?

A

its lactam ring (binds with a serine residue at the active site

39
Q

How can heavy metals inhibit enzyme reactions?

A

they bind to a functional group in an enzyme (lead and mercury inhibit -SH groups)

40
Q

What are enzymes that are regulated by effectors and bind to sites other than the active site?

A

allosteric enzymes

41
Q

What kind of bonds do allosteric enzymes make with its sites?

A

non-covalent

42
Q

What kind of curve does an allosteric enzyme make?

A

sigmoid (not Km curve)

43
Q

What is the main purpose of allosteric enzymes?

A

show positive cooperativity (binding to one subunit promotes binding to another subunit)

44
Q

What is the T (tense) conformation of allosteric enzymes?

A

lowers affinity for binding to inhibitors

45
Q

What is the R (relaxed) conformation of allosteric enzymes?

A

raises affinity for binding to activators

46
Q

What catalyzes phosphorylation?

A

protein kinases (uses ATP to get a phosphate)

47
Q

Which enzymes cleave/split phosphate groups (dephosphorylation)?

A

phospho-protein phosphatases

48
Q

During cell death where do their intracellular enzymes get secreted into?

A

the blood!

49
Q

What are normal blood enzymes called?

A

zymogens (precursors for coagulation)

50
Q

Liver damage increases the count of what enzyme in the blood?

A

alanine aminotransferase

51
Q

Acute pancreatitis increases the count of what enzymes in the blood?

A

amylase and lipase

52
Q

The presence of what enzyme can be used to diagnose myocardial infarctions?

A

creatine kinase

biochem midterm (9 decks)

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