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Biochem 2 > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

enzyme inhibitors

A
  • endogenous inhibitors control mechanisms for biological systems (drugs and toxins)
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2
Q

irreversible inhibition

A

inhibitor is covalently linked to enzyme or bound so tightly dissociate from enzyme is very slow

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3
Q

reversible inhibition

A
  • rapid binding equilibrium between enzyme and inhibitor
  • enzyme activity fully restored when inhibitor is removed
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4
Q

what are the two types of reversible inhibitors?

A

competitive and nonceompetitive

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5
Q

examples of irreversible inhibitors

A

aspirin, nerve gas (DPF)

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6
Q

what groups are present on enzymes that can be inhibited by irreversible inhibitors?

A

seryl hydroxyl groups

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7
Q

what effect is there for the inhibition of COX2?

A

increases rates of heart attack

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8
Q

what part of aspirin is inhibited?

A

COX1 and COX2

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9
Q

Reversible competitive inhibitor

A

resembles the substrate and binds to active site
- completes with normal substrate
- diminishes rate of catalysis by reducing proportion of enzyme molecules that have bound substrate

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10
Q

what happens if DPF is inhibited?

A

leads to paralysis of the muscle
- causes respiratory failure

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11
Q

Reversible noncompetitive inhibitors

A
  • binds to site on enzyme other than the active site
  • alters the structure of the enzyme
    enzyme still bind substrate in presence of inhibitor but is unable to catalyze reaction
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12
Q

how can competitive inhibition be used?

A

treating forms of intoxication: methanol (confused for alcohol) and ethylene glycol intoxication (antifreeze)

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13
Q

what organ metabolizes methanol?

A

liver and kidney

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14
Q

what are some effects of ethylene glycol?

A

depression of CNS, metabolic acidosis, renal damage, oxalate crystals

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15
Q

examples of noncompetitive inhibitors

A

enzymes with -SH (sulfhydryl) group (silver, lead, mercury), cleating agents

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16
Q

hydrolase

A

enzymes that catalyze hydrolytic cleavage reaction

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17
Q

proteases

A

degrade proteins by hydrolyzing bonds between amino acids

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18
Q

nucleases

A

degrade nucleic acids by hydrolyzing bonds between nucleotides

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19
Q

synthtases

A

synthesize molecules in anabolic reactions by joining two smaller molecules

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20
Q

isomerases

A

catalyze the rearrangement of bonds within a single molecule

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21
Q

polymerases

A

catalyze polymerization reactions in RNA and DNA synthesis

22
Q

oxido-reductases

A

catalyze oxidation/reduction reactions (oxidase, reductases, dehydrogenases)

23
Q

kinases

A

catalyzes transfer of a phosphate group from ATP to other molecules

24
Q

phosphatases

A

catalyze the hydrolytic removal of phosphate groups from molecules

25
Q

ATPases

A

catalyze the hydrolysis of ATP

26
Q

what regulates enzyme activity?

A

concentration of enzyme and substrate, temperature, pH, coenzymes, prosthetic groups, cofactors, phosphorylation/dephosphorylation, zymogen activation

27
Q

optimal pH for proteins

A

between pH 6 and pH 8 (human blood 7.4)

28
Q

what pH does pepsin function at?

A

pH 2 –> it is a acidic gastric secretion

29
Q

how does pH affect proteins?

A
  • affects the charge
  • affects binding of substrate to active site
  • affects catalytic mechanism of enzyme itself
30
Q

cofactor

A
  • inorganic ions or low-molecular weight organic (nonprotein) or metalloorganic molecules
  • bind through non-covalent interactions
31
Q

how are prosthetic groups linked?

A

bound to enzymes by covalent linkages (tightly attached)

32
Q

metal cofactors

A
  • metal ions which can serve as electron pair acceptors
  • form coordination bonds with enzymes that help properly position reactive groups during catalysis
33
Q

what is phosphorylation?

A

addition of phosphate group to the side-chain hydroxyl groups of serine, theronine and tyrosine residues

34
Q

how does phosphorylation affect enzyme activity?

A

depending on enzyme, phosphorylation can increase or decrease enzyme activity

35
Q

what is a zymogen?

A

inactive precursor of enzymes

36
Q

how are zymogens activated?

A

proteolytic cleavage of covalent bonds within precursor sequence

37
Q

what enzymes are synthesized as zymogens?

A

digestive enzymes –> made in the stomach and pancreas

38
Q

what enzyme produces trypsin?

A

trypsinogen –> cleavage by enzyme enteropeptidase

39
Q

where is enteropeptidase located?

A

brush border of duodenal mucosa

40
Q

pancreatic proteases are synthesized as inactive zymogens (T/F)

A

T

41
Q

how does the pancreas protect itself from enzymes?

A
  • zymogens packaged in lipid membrane bounded by secretory granules
  • potent trypsin inhibitor, binds to active site of trypsin, blocking activity
42
Q

acute pancreatitis

A

premature activation of the proteolytic and lipolytic enzymes of pancreas –> leads to destruction of pancreas

43
Q

where are lysozymes found?

A

enzyme found in egg white, saliva, tears and other secretions

44
Q

what does lysozyme do?

A

catalyzes the cutting of polysaccharide chains in cell walls of bacteria

45
Q

what is creatine kinase associated with?

A

ATP regeneration in contractile or transport systems

46
Q

what is the function of creatine kinase?

A

storage of high energy creatine phosphate in muscle

47
Q

where is creatine kinase found?

A

skeletal muscle, heart muscle and brain

48
Q

what are the three major forms of creatine kinase isoenzymes?

A

CK-BB (brain type –> brain and other tissue)
CK-MM (muscle type –> heart and skeletal muscle
CK-MB (hybrid type–> heart and small amount in skeletal muscle)

49
Q

what diseases are associated with high creatine kinase levels?

A

acute myocardial infarction (AMI), muscular dystrophy, hypothyroidism

50
Q

what disease does elevated serum CK-MM indicate?

A

skeletal or cardiac muscle injury –> strenuous physical activity or intramuscular injections

51
Q

what disease does elevated serum CK-BB indicate?

A

damage to CNS, tumors, childbirth

52
Q

which creatine kinase isoenzyme is the major form in serum?

A

CK-MM: makes up 94-100%

Biochem 2 (5 decks)

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