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IUSM Biochemistry > Enzymes > Flashcards

Enzymes Flashcards

1
Q

Enzymes enhance reaction _______ but do not change the ________.

A

Rates; Equilibrium

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2
Q

What is the name of the enzyme that is used as a monitor for liver and kidney disease? It is normally a cytoplasmic enzyme most abundant in liver and is released into the blood after liver damage.

A

Alanine amino transferase (ALT or ALAT)

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3
Q

Enzymes lower free energy of activation by stabilizing ______?

A

The transition state

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4
Q

What are transition state analogs?

A

Stable molecules that look similar to the transition state, often used to make drugs.
EX = allopurinol is used to inhibit xanthine oxidase to treat Gout

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5
Q

Binding of substrate by the enzyme increases the _____ of the substrate.

A

effective concentration

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6
Q

What are the two types of enzyme catalysis?

A

Acid-Base and covalent

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7
Q

What does an amylase do?

A

Breaks down carbohydrates

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8
Q

Digestive proteases are activated by?

A

Specific proteolytic cleavage

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9
Q

Proteolytic digestive enzymes are synthesized as inactive precursors (________) that are activated after secretion

A

zymogens

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10
Q

Is pancreatic lipase a zymogen?

A

No

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11
Q

Are trypsin and chymotrypsin zymogens?

A

Yes

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12
Q

What three amino acids make up the catalytic triad for proteolytic cleavage enzymes?

A

Asparate, Histidine, Serine

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13
Q

What proteolytic cleavage enzyme activates chymotrypsin?

A

serine protease

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14
Q

Reversible inhibitors interact with an enzyme via ______ associations while irreversible interact via _______ associations

A

noncovalent, covalent

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15
Q

What are the three types of reversible inhibitors?

A

Competitive, Noncompetitive, uncompetitive

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16
Q

A competitive inhibitor binds to?

A

The enzyme’s active site

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17
Q

A noncompetitive inhibitor binds to?

A

Either the enzyme or the enzyme substrate complex

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18
Q

An uncompetitive inhibitor binds only to?

A

The enzyme substrate complex

19
Q

A competitive inhibitor ______ Km and _______ Vmax

A

Increases Km but does not change Vmax

20
Q

What is the committed step for cholesterol synthesis?

A

The synthesis of mevalonate

21
Q

What enzyme synthesizes mevalonate and in turn is necessary for cholesterol synthesis?

A

HMG-CoA reductase

22
Q

What type of drugs are used to inhibit HMG-CoA reductase to decrease blood cholesterol?

A

Statins

23
Q

What type of inhibitors are statins?

A

competitive - they are shaped like mevalonate

24
Q

Nerve gas is what type of enzymatic inhibitor? what does it inhibit?

A

Irreversible

Acetylcholinesterase

25
Q

What are muscarinic acetylcholine receptors?

A

Main G-protein receptor complex in neurons of the PNS

26
Q

What activates muscarinic receptors of neurons?

A

Acetylcholine

27
Q

What enzyme metabolizes acetylcholine?

A

Acetylcholinesterase

28
Q

What happens if acetylcholinesterase is inhibited?

A

PNS problems, such as rigor mortis and paralysis

29
Q

What is the antidote for acetylcholinesterase inhibitors like nerve gas and parathion?

A

Atropine, it blocks access to muscarinic receptors

30
Q

Asprin is an irreversible inhibitor of what 2 enzymes?

A

COX-2 and COX-1

31
Q

Why does Asprin cause stomach problems?

A

COX-1 which it inhibits, is essential for stomach health

32
Q

What type of enzyme responds differently to different substrate concentrations?

A

Isozymes

33
Q

What two isozymes phosphorylate glucose?

A

Hexokinase (RBC)

Glucokinase (Liver)

34
Q

Which has a lower km hexokinase or glucokinase?

A

Hexokinase (RBC) has a low Km while glucokinase (liver) has a high Km. This ensures that RBCs get glucose when concentrations are low.

35
Q

What do Kinases do?

A

Add phosphate

36
Q

What do phosphatases do?

A

Removes phosphate

37
Q

What three amino acids can be phosphorylated?

A

serine, threonine, tyrosine

38
Q

What is the most common example of reversible covalent modification?

A

Phosphorylation/dephosphorylation of ser, thr, tyr

39
Q

What is the regulated enzyme of fatty acid synthesis?

A

Acetyl CoA carboxylase

40
Q

What is the end product of fatty acid synthesis and is also a feedback inhibitor of Acetyl CoA carboxylase?

A

Palmitoyl CoA

41
Q

Do allosteric enzymes obey Michaelis-Menten Kinetics?

A

No

42
Q

What does a allosteric enzyme substrate/reaction velocity curve look like?

A

Sigmoidal

43
Q

What is a key trait of allosteric enzymes?

A

They display cooperativity - activity of one functional site affects the activity at other sites

44
Q

What is Phosphofructokinase 1 (PFK1) activated by allosterically?

A

AMP

IUSM Biochemistry (11 decks)

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