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Cellular Biochemistry > Chapter 18 > Flashcards

Chapter 18 Flashcards

1
Q

What converts N2 –> NH3

also NH3 –> NH4+

A

Nitrogenase

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2
Q

Nitrogen fixing organisms

A

Diazotrophs: Marine cyanobacteria/root nodule bacteria that make nitrogenase

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3
Q

Biological productivity is limited by …

A

availability of fixed N₂

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4
Q

Nitrogenase structure

A

Iron-sulfur centers
Cofactor with both iron and molybdenum (FeMo)

needs 8e-
consumes 16 ATP

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5
Q

FeMo cofactor: What does it do?

A

Facilitates breaking through triple bonds in N, requires strong reducing agents such as donor (ferredoxin). Consumes ATP. Needs 8e-

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6
Q

What inactivates nitrogenase

A

Oxygen

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7
Q

Oxidation of NH4+ –> NO3-

A

Nitrification (Nitrogen reductase)

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8
Q

Conversion of NO3- to N2

A

Denitrification

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9
Q

GluatMINE synthEtase

A

Microorganisms: entry point for fixed nitrogen

Animals: absorbs excess ammonia, which is toxic

Step 1: ATP donates phosphoryl group to glutamate

Step 2: Ammonia reacts with intermediate, displacing Pi to make glutamine
ATP consumed

Glu/Gln = amino group carriers (in high concentration)

Activity tightly regulated to maintain supply of amino groups

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10
Q

____ assimilates fixed nitrogen as NH₄+ into organic compound (CAC intermediate) to make amino acid

A

Combination of Gln synthetase and glu synthase

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11
Q

Glutamate synthase

A

Exchange amine group
Transfer 2nd NH2 to alpha ketoglutarate

Creates 2 glutamates

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12
Q

How do amino acids move between compounds?

A

Transaminase

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13
Q

Only amino acid that can’t be transaminated?

A

Lysine

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14
Q

Most transaminases only accept __________________ as the alpha-keto acid substrate

A

alpha-ketoglutarate or oxaloacetate

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15
Q

What is the acid/base catalyst in transaminase?

A

Enzyme Lys, acts as schiff

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16
Q

Transaminase cofactors

A

Requires PLP prosthetic group for transient attachment
Derivative of pyridoxine (Vitamin B₆)
Covalently attached to enzyme via schiff base (imine) linkage to Lys residue

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17
Q

Nonessential (define)

A

we make it

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18
Q

Essential (define)

A

we need to eat it

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19
Q

Nonessential (list)

A

A’s, G’s,
Promote, Serious, Roses
(proline, serine, tyrosine)

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20
Q

Essential (list)

A

HILL
MVP
There’s 9 Tries

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21
Q

Branched Essentials from pyruvate – >

A

Valine, Isoleucine, Leucine

Val, Ile, Leu (VIL)

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22
Q

Aspartate Essentials – >

A

Already have head group

Lysine, Methionine, Threonine
(LET ME THRive to what I ASPire)

Lys, Met, Thr (K, M, T)

23
Q

PEP + Erythrose-4-phosphate –> Chorismate

Condensation C3/C4

Essential

A

Phenylalanine, Tryptophan

Phe, Trp
F, W

24
Q

ATP + glu and gln + PRPP

Essential

ATP provides 1 N and 1 C
Glutamate/Glutamine donate other 2 N
PRPP gives other 5 C

A

Histidine

His, H

25
Q

Name the 3 nonessential transamination

A

1) Pyruvate –> Alanine
2) Oxaloacetate –> AsparatATE (asp)
3) Alpha-Ketoglutarate –> GlutamATE (glu)

26
Q

What 3 nonessentials can glutamate make?

A

Arginine, Glutamine, Proline

27
Q

Glutamine + Aspartate (nonessential)

A

Asparagine (+ glutamate)

28
Q

3-phosphoglycerate (glycolytic intermediate)

nonessential

A

Serine

29
Q

Serine (nonessential precursor to what)

A

glycine

30
Q

Methionine/Homocystine thing

nonessential precursor

A

Cysteine

31
Q

Phenylalanine (Chrisimate)

A

Tyrosine

32
Q

Signaling Molecules precursors

A

Tyrosine → Dopamine, Norepinephrine, and Epinephrine

Tryptophan → Serotonin → Melatonin

Arginine → Nitric Oxide

33
Q

When are amino acids partially oxidized substrates for gluconeogenesis or ketogenesis

A

During fast when not enough oxygen available for the liver to completely oxidize all carbon to CO2.

34
Q

Glucogenic-

The large skeletons of aromatic amino acids are both glucogenic and ketogenic

A

giving rise to gluconeogenic precursors such as CAC intermediates

Most nonessential

35
Q

Ketogenic

A

giving rise to acetyl-CoA which can be used for ketogenesis or fatty acid synthesis, but not gluconeogenesis

36
Q

Only two ketogenically exclusive amino acids

A

Leucine and Lysine

37
Q

Which are both ketogenic and glucogenic?

A

All t’s
Isoleucine
Phenylalanine
Aromatic rings

38
Q

Glucogenic: only makes succinyl-CoA?

A

Methionine and Valine

39
Q

Glucogenic: only makes pyruvate

A

Alanine, Serine, Cysteine

40
Q

Glucogenic Only:

Aspartate –> oxaloacetate

A

Aspartate (duh)

Asparagine

41
Q

Glucogenic only: Glutamate –> Alpha-ketoglutarate

A 
Arginine
Glutamate
Glutamine
Histidine
Proline
42
Q

Glucogenic only: Glycine thing

A

Glycine –> Co2

Glycine cleave system, multicomplex enzyme with tetrahydrofolate

43
Q

Isoleucine –>

Threonine –>

A

Iso: Succinyl-CoA and acetyl-CoA

Threonine: glycine and acetyl-CoA

44
Q

Leucine/Lysine –>

A

acetyl-CoA and acetoacetate

45
Q

Phenylalanine/Tryptophan/Tyrosine –>

A

acetoacetate and either fumarate or pyruvate

Uses cofactors tetrahydrobiopterin. Like folate contains pterin group

46
Q

Two entry points for aminos into urea cycle

A

Glutamate in mitochondria

Cytosol as aspartate

47
Q

major site of glutamine catabolism

A

Kidney

48
Q

___ supplies nitrogen to urea cycle

A

glutamate,

49
Q

What is the primary regulatory step for generation of entry point in urea cycle?

A

Carbamoyl phosphate synthetase reaction

50
Q

Urea cycle uses __ to activate bicarbonate unit

A

ATP

51
Q

What is the regulator of carbamoyl phosphate synthetase reaction?

A

N-acetyl-glutamate

Inherent metabolic sensor

52
Q

How do you increase flux in urea cycle?

A

Increase intermediates by carbamoyl phosphate synthetase

53
Q

Cost of Urea cycle

A

4 ATP per Urea

Cellular Biochemistry (15 decks)

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