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Elements of Medicine > Hemoglobin/Enzymes > Flashcards

Hemoglobin/Enzymes Flashcards

1
Q

What is Iron (II) called?

A

Ferrous oxidation state

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2
Q

What is Iron (III) called?

A

Ferric oxidation state

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3
Q

Heme is..

A

A protoporphyrin IX containing a bound Iron

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4
Q

Is the heme iron in the porphyrin when oxygen is bound or when it’s not?

A

When O2 is bound

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5
Q

Bohr Effect

A

When [H+] is increased (pH is lower), causing hemoglobin to release oxygen

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6
Q

Which state do you have a salt bridge in hemoglobin?

A

T state

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7
Q

Histidine 146 forms a salt bridge with what residue at lower pH?

A

Asp 94 (number probably not important)

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8
Q

Where does CO2 bind to hemoglobin to become carbamate?

A

amino (N) terminus

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9
Q

Which enzyme converts 1,3-BPG from glycolysis to 2,3-BPG?

A

2,3-Bisphospho glycerate mutase

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10
Q

Which tissues can you find 2,3-Bisphospho clycerate mutase

A

Erythrocytes and placenta

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11
Q

Why does CO have greater affinity to hemoglobin than O2

A

It has a lone electron pair to donate to Fe (II)’s d-orbitals. Also binds perpendicularly rather than at an angle

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12
Q

Tibetans have a mutation in what protein due to higher NO levels?

A

Endothelial PAS Domain-counting protein 1 (EPAS1)

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13
Q

What is it called when the heme is oxidized to Fe3+

A

Methemoglobin

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14
Q

The name of the enzyme which reduces methemoglobin to hemoglobin

A

NADH-methemoglobin reductase

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15
Q

What is a deficiency in NADH-methemoglobin reductase called?

A

Cyanosis

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16
Q

Which drugs can cause a decrease in NADH-methemoglobin reductase?

A

Benzocaine, dapsone, and nitrates

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17
Q

Methemoglobinemia can also be caused by…

A

reactive oxygen intermediates and inherited defects

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18
Q

What is a treatment for severe cyanosis?

A

Methylene blue

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19
Q

What is the mutation in sickle cell anemia?

A

Glu6Val

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20
Q

What is Hemoglobin C?

A

Mutation of Glu6-> Lys6, but they’re both polar so no sickling. mild hemolytic anemia, no biggie.

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21
Q

Two treatments for HbS?

A
  1. Silencing BCL11A, which normally suppresses HbF

2. Hydroxyurea, which increases HbF expression

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22
Q

What does the distal histidine do during CO binding to hemoglobin?

A

Steric hindrance; relatively decreases affinity.

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23
Q

Type of reaction catalyzed by… oxidoreductases

A

Transfer of electrons

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24
Q

Type of reaction catalyzed by… transferases

A

Group transfer reactions

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25
Q

Type of reaction catalyzed by… hydrolases

A

Hydrolysis reactions (transfer of functional groups to water)

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26
Q

Type of reaction catalyzed by… lyases

A

Cleavage of C-C, C-O, C-N or other bonds by elimation. Leaves a double bond or ring, or addition of other groups to double bond.

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27
Q

Type of reaction catalyzed by… Isomerases

A

transfer of groups within molecules to yield isomers

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28
Q

Type of reaction catalyzed by… ligases

A

Formation of C-C, C-S, C-O, and C-N bonds by condensation reaction coupled to cleavage of ATP or similar cofactor

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29
Q

What complex similar to iron-sulfur clusters is present in mitochondrial proteins?

A

Fe-Cu centers

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30
Q

What does FAD carry?

A

Electrons

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31
Q

What is FAD’s dietary precursor?

A

Riboflavin (Vitamin B2)

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32
Q

What does NAD carry?

A

Hydride Ion

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33
Q

What is the dietary precursor of NAD?

A

Niacin

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34
Q

What does Tetrahydrofolate carry?

A

One carbon groups

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35
Q

What is tetrahydrofolate’s dietary precursor?

A

Folate

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36
Q

What does thiamine pyrophosphate carry?

A

Aldehydes

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37
Q

What is thiamine pyrophosphate’s dietary precursor?

A

Thiamine

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38
Q

What is the disorder caused by a deficiency of thiamine?

A

Beriberi

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39
Q

What is an apoenzyme?

A

Enzyme without the factor

40
Q

What is a holoenzyme?

A

Complete, active enzyme with prosthetic group/etc..

41
Q

What does Coenzyme A carry?

A

Acyl groups

42
Q

What is the metabolic function of pyruvate dehydrogenase?

A

pyruvate to acetyl coA

43
Q

Three enzymes in the PDH complex?

A

E1: Pyruvate dehydrogenase
E2: Dihydrolipoyl transacetylase
E3: Dihydrolipoyl dehydrogenase

44
Q

Coenzymes/cofactors of PDH complex:

A

TPP, Lipoamide, CoA, NAD+, FAD

45
Q

What is a niacin deficiency called?

A

Pellagra

46
Q

Which amino acid can niacin be derived from?

A

Tryptophan

47
Q

What does a deficiency of tetrahydrofolate cause?

A

Spina bifida and low birth weight

48
Q

Name the four enzyme catalysis mechanisms

A
  1. Catalysis by proximity
  2. Acid-base catalysis
  3. Catalysis by strain
  4. Covalent catalysis
49
Q

Aspartic proteases use what catalytic mechanism?

A

Acid-base catalysis (hey the shit in HIV is of this family?)

50
Q

What is the catalytic mechanism in serine proteases?

A

Covalent catalysis

51
Q

What residues are involved in proton shuttling?

A

Asp-His-Ser

52
Q

Function of aspartate in catalytic activity

A

Cation binding and proton transfer

53
Q

Function of glutamate in catalytic activity

A

Cation binding and proton transfer

54
Q

Function of histidine in catalytic activity

A

proton transfer

55
Q

Function of cysteine in catalytic activity

A

Covalent binding of acyl groups (nucleophile)

56
Q

Function of tyrosine in catalytic activity

A

Hydrogen bonding to ligans

57
Q

Function of lysine in catalytic activity

A

Anion binding and proton transfer

58
Q

Function of arginine in catalytic activity

A

Anion binding

59
Q

Function of serine in catalytic activity

A

Covalent binding of acyl groups (nucleophile)

60
Q

Lactate dehydrogenase has how many isozymes?

A

5

61
Q

LDHA Subunit M

A

Muscle. Favors reduction of pyruvate to lactate. LDH5 has all M subunit.

62
Q

LDHA Subunit H

A

Heart. Favors oxidation of lactate into pyruvate. LDH1 has all H subunit.

63
Q

What wavelength does NADPH/NADH absorb?

A

340 nm

64
Q

What is the reaction order at vmax?

A

Zero order

65
Q

Michaelis-Menten Equation

A

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

66
Q

What is the turnover number?

A

Kcat (number of substrate molecules converted to product per enzyme molecule per unit of time)

67
Q

Kcat = ?

A

Vmax/[E]

68
Q

What is the specificity constant?

A

Kcat/Km

69
Q

What is the x-intercept of a lineweaver-burke plot?

A

-1/Km

70
Q

What is the y-intercept of a lineweaver-burke plot?

A

1/Vmax

71
Q

A protein complex consisting of the enzyme and two substrates

A

Ternary complex

72
Q

Which multi-substrate enzyme mechanism does not form a ternary complex?

A

Ping-pong mechanism

73
Q

What is a double displacement or ping-pong mechanism?

A

One or more products are released from the enzyme before all the substrates have been added.

74
Q

What does an intersecting line indicate for a multi-substrate reaction?

A

a ternary complex

75
Q

What does the graph look like for a ping-pong mechanism?

A

parallel lines

76
Q

What are the four types of irreversible inhibition?

A
  1. competitive
  2. uncompetitive
  3. mixed
  4. non competitive
77
Q

Competitive inhibition

A

Same Vmax, different Km

78
Q

Noncompetitive inhibition

A

Decreases Vmax, same Km

79
Q

Mixed inhibition

A

Both Vmax and Km can change. Lines may intersect

80
Q

Uncompetitive inhibition

A

Lines are parallel. Km/Vmax ratio stays the same. Inhibitor binds only to the ES complex.

81
Q

Methotrexate

A

chemical similar to folic acid (THF), inhibits DNA synthesis

82
Q

Arsenite

A

noncompetitive inhibitor, blocks catalytic activity of enzymes such as PDH and A-KG dehydrogenase.

83
Q

What do statins inhibit?

A

HMG-CoA reductase. COMPETITIVE inhibitor

84
Q

Penicillin’s inhibition mechanism?

A

Basically is an irreversible inhibitor of transpeptidases in bacteria

85
Q

What inhibits thymidylate synthase (inhibiting DNA/RNA synthesis)? (Hint: topical cream)

A

Fluorouracil. Used to treat skin cancer.

86
Q

Four ways of enzyme regulation?

A
  1. Association with regulatory protein
  2. sequestration
  3. allosteric regulation
  4. covalent modification
87
Q

When is enzyme regulation most effective (chemically)

A

Around Km

88
Q

Regulation via the substrate of an enzyme is called…

A

a homotropic allosteric regulator

89
Q

Regulation via a molecule which is not the substrate of an enzyme is called…

A

a heterotropic allosteric regulator

90
Q

Advantages of regulation by reversible PTMs (3)

A

1) fast
2) does not require new protein synthesis or degradation
3) easily reversible

91
Q

Small molecules inhibitors of what are used for cancer treatment?

A

tyrosine kinases

92
Q

What enzyme catalyzes the transfer of an acetyl group from acetyl-CoA to the episilon-amino groups of lysyl residues

A

Lysine acetyltransferases

93
Q

What does acetylation due that is significant?

A

neutralizes the positive charges on Lys residues. changes the conformation/activity like this.

94
Q

What is the irreversible mechanism called “processing” known as, that is used for the rapid mobilization of an activity?

A

Limited proteolysis

95
Q

What do some zymogens undergo (think blood coagulation) to activate them?

A

N and C terminal processing

Elements of Medicine (8 decks)

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