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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
Type of reaction catalyzed by... hydrolases
Hydrolysis reactions (transfer of functional groups to water)
26
Type of reaction catalyzed by... lyases
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.
27
Type of reaction catalyzed by... Isomerases
transfer of groups within molecules to yield isomers
28
Type of reaction catalyzed by... ligases
Formation of C-C, C-S, C-O, and C-N bonds by condensation reaction coupled to cleavage of ATP or similar cofactor
29
What complex similar to iron-sulfur clusters is present in mitochondrial proteins?
Fe-Cu centers
30
What does FAD carry?
Electrons
31
What is FAD's dietary precursor?
Riboflavin (Vitamin B2)
32
What does NAD carry?
Hydride Ion
33
What is the dietary precursor of NAD?
Niacin
34
What does Tetrahydrofolate carry?
One carbon groups
35
What is tetrahydrofolate's dietary precursor?
Folate
36
What does thiamine pyrophosphate carry?
Aldehydes
37
What is thiamine pyrophosphate's dietary precursor?
Thiamine
38
What is the disorder caused by a deficiency of thiamine?
Beriberi
39
What is an apoenzyme?
Enzyme without the factor
40
What is a holoenzyme?
Complete, active enzyme with prosthetic group/etc..
41
What does Coenzyme A carry?
Acyl groups
42
What is the metabolic function of pyruvate dehydrogenase?
pyruvate to acetyl coA
43
Three enzymes in the PDH complex?
E1: Pyruvate dehydrogenase E2: Dihydrolipoyl transacetylase E3: Dihydrolipoyl dehydrogenase
44
Coenzymes/cofactors of PDH complex:
TPP, Lipoamide, CoA, NAD+, FAD
45
What is a niacin deficiency called?
Pellagra
46
Which amino acid can niacin be derived from?
Tryptophan
47
What does a deficiency of tetrahydrofolate cause?
Spina bifida and low birth weight
48
Name the four enzyme catalysis mechanisms
1. Catalysis by proximity 2. Acid-base catalysis 3. Catalysis by strain 4. Covalent catalysis
49
Aspartic proteases use what catalytic mechanism?
Acid-base catalysis (hey the shit in HIV is of this family?)
50
What is the catalytic mechanism in serine proteases?
Covalent catalysis
51
What residues are involved in proton shuttling?
Asp-His-Ser
52
Function of aspartate in catalytic activity
Cation binding and proton transfer
53
Function of glutamate in catalytic activity
Cation binding and proton transfer
54
Function of histidine in catalytic activity
proton transfer
55
Function of cysteine in catalytic activity
Covalent binding of acyl groups (nucleophile)
56
Function of tyrosine in catalytic activity
Hydrogen bonding to ligans
57
Function of lysine in catalytic activity
Anion binding and proton transfer
58
Function of arginine in catalytic activity
Anion binding
59
Function of serine in catalytic activity
Covalent binding of acyl groups (nucleophile)
60
Lactate dehydrogenase has how many isozymes?
5
61
LDHA Subunit M
Muscle. Favors reduction of pyruvate to lactate. LDH5 has all M subunit.
62
LDHA Subunit H
Heart. Favors oxidation of lactate into pyruvate. LDH1 has all H subunit.
63
What wavelength does NADPH/NADH absorb?
340 nm
64
What is the reaction order at vmax?
Zero order
65
Michaelis-Menten Equation
V = Vmax*[S] / Km + [S]
66
What is the turnover number?
Kcat (number of substrate molecules converted to product per enzyme molecule per unit of time)
67
Kcat = ?
Vmax/[E]
68
What is the specificity constant?
Kcat/Km
69
What is the x-intercept of a lineweaver-burke plot?
-1/Km
70
What is the y-intercept of a lineweaver-burke plot?
1/Vmax
71
A protein complex consisting of the enzyme and two substrates
Ternary complex
72
Which multi-substrate enzyme mechanism does not form a ternary complex?
Ping-pong mechanism
73
What is a double displacement or ping-pong mechanism?
One or more products are released from the enzyme before all the substrates have been added.
74
What does an intersecting line indicate for a multi-substrate reaction?
a ternary complex
75
What does the graph look like for a ping-pong mechanism?
parallel lines
76
What are the four types of irreversible inhibition?
1. competitive 2. uncompetitive 3. mixed 4. non competitive
77
Competitive inhibition
Same Vmax, different Km
78
Noncompetitive inhibition
Decreases Vmax, same Km
79
Mixed inhibition
Both Vmax and Km can change. Lines may intersect
80
Uncompetitive inhibition
Lines are parallel. Km/Vmax ratio stays the same. Inhibitor binds only to the ES complex.
81
Methotrexate
chemical similar to folic acid (THF), inhibits DNA synthesis
82
Arsenite
noncompetitive inhibitor, blocks catalytic activity of enzymes such as PDH and A-KG dehydrogenase.
83
What do statins inhibit?
HMG-CoA reductase. COMPETITIVE inhibitor
84
Penicillin's inhibition mechanism?
Basically is an irreversible inhibitor of transpeptidases in bacteria
85
What inhibits thymidylate synthase (inhibiting DNA/RNA synthesis)? (Hint: topical cream)
Fluorouracil. Used to treat skin cancer.
86
Four ways of enzyme regulation?
1. Association with regulatory protein 2. sequestration 3. allosteric regulation 4. covalent modification
87
When is enzyme regulation most effective (chemically)
Around Km
88
Regulation via the substrate of an enzyme is called...
a homotropic allosteric regulator
89
Regulation via a molecule which is not the substrate of an enzyme is called...
a heterotropic allosteric regulator
90
Advantages of regulation by reversible PTMs (3)
1) fast 2) does not require new protein synthesis or degradation 3) easily reversible
91
Small molecules inhibitors of what are used for cancer treatment?
tyrosine kinases
92
What enzyme catalyzes the transfer of an acetyl group from acetyl-CoA to the episilon-amino groups of lysyl residues
Lysine acetyltransferases
93
What does acetylation due that is significant?
neutralizes the positive charges on Lys residues. changes the conformation/activity like this.
94
What is the irreversible mechanism called "processing" known as, that is used for the rapid mobilization of an activity?
Limited proteolysis
95
What do some zymogens undergo (think blood coagulation) to activate them?
N and C terminal processing

Elements of Medicine (8 decks)

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