Chapter 18

Question 1

What converts N2 –> NH3

also NH3 –> NH4+

Answer 1

Nitrogenase

Question 2

Nitrogen fixing organisms

Answer 2

Diazotrophs: Marine cyanobacteria/root nodule bacteria that make nitrogenase

Question 3

Biological productivity is limited by …

Answer 3

availability of fixed N₂

Question 4

Nitrogenase structure

Answer 4

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

needs 8e-
consumes 16 ATP

Question 5

FeMo cofactor: What does it do?

Answer 5

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

Question 6

What inactivates nitrogenase

Answer 6

Oxygen

Question 7

Oxidation of NH4+ –> NO3-

Answer 7

Nitrification (Nitrogen reductase)

Question 8

Conversion of NO3- to N2

Answer 8

Denitrification

Question 9

GluatMINE synthEtase

Answer 9

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

Question 10

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

Answer 10

Combination of Gln synthetase and glu synthase

Question 11

Glutamate synthase

Answer 11

Exchange amine group
Transfer 2nd NH2 to alpha ketoglutarate

Creates 2 glutamates

Question 12

How do amino acids move between compounds?

Answer 12

Transaminase

Question 13

Only amino acid that can’t be transaminated?

Answer 13

Lysine

Question 14

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

Answer 14

alpha-ketoglutarate or oxaloacetate

Question 15

What is the acid/base catalyst in transaminase?

Answer 15

Enzyme Lys, acts as schiff

Question 16

Transaminase cofactors

Answer 16

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

Question 17

Nonessential (define)

Answer 17

we make it

Question 18

Essential (define)

Answer 18

we need to eat it

Question 19

Nonessential (list)

Answer 19

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

Question 20

Essential (list)

Answer 20

HILL
MVP
There’s 9 Tries

Question 21

Branched Essentials from pyruvate – >

Answer 21

Valine, Isoleucine, Leucine

Val, Ile, Leu (VIL)

Question 22

Aspartate Essentials – >

Answer 22

Already have head group

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

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

Question 23

PEP + Erythrose-4-phosphate –> Chorismate

Condensation C3/C4

Essential

Answer 23

Phenylalanine, Tryptophan

Phe, Trp
F, W

Question 24

ATP + glu and gln + PRPP

Essential

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

Answer 24

Histidine

His, H

Question 25

Name the 3 nonessential transamination

Answer 25

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

Question 26

What 3 nonessentials can glutamate make?

Answer 26

Arginine, Glutamine, Proline

Question 27

Glutamine + Aspartate (nonessential)

Answer 27

Asparagine (+ glutamate)

Question 28

3-phosphoglycerate (glycolytic intermediate) | nonessential

Answer 28

Serine

Question 29

Serine (nonessential precursor to what)

Answer 29

glycine

Question 30

*Methionine*/Homocystine thing | nonessential precursor

Answer 30

Cysteine

Question 31

*Phenylalanine* (Chrisimate)

Answer 31

Tyrosine

Question 32

Signaling Molecules precursors

Answer 32

Tyrosine → Dopamine, Norepinephrine, and Epinephrine Tryptophan → Serotonin → Melatonin Arginine → Nitric Oxide

Question 33

When are amino acids partially oxidized substrates for gluconeogenesis or ketogenesis

Answer 33

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

Question 34

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

Answer 34

giving rise to gluconeogenic precursors such as CAC intermediates Most nonessential

Question 35

Ketogenic

Answer 35

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

Question 36

Only two ketogenically exclusive amino acids

Answer 36

Leucine and Lysine

Question 37

Which are both ketogenic and glucogenic?

Answer 37

All t's Isoleucine Phenylalanine Aromatic rings

Question 38

Glucogenic: only makes succinyl-CoA?

Answer 38

Methionine and Valine

Question 39

Glucogenic: only makes pyruvate

Answer 39

Alanine, Serine, Cysteine

Question 40

Glucogenic Only: | Aspartate --> oxaloacetate

Answer 40

Aspartate (duh) | Asparagine

Question 41

Glucogenic only: Glutamate --> Alpha-ketoglutarate

Answer 41

``` Arginine Glutamate Glutamine Histidine Proline ```

Question 42

Glucogenic only: Glycine thing

Answer 42

Glycine --> Co2 | Glycine cleave system, multicomplex enzyme with tetrahydrofolate

Question 43

Isoleucine --> | Threonine -->

Answer 43

Iso: Succinyl-CoA and acetyl-CoA Threonine: glycine and acetyl-CoA

Question 44

Leucine/Lysine -->

Answer 44

acetyl-CoA and acetoacetate

Question 45

Phenylalanine/Tryptophan/Tyrosine -->

Answer 45

acetoacetate and either fumarate or pyruvate Uses cofactors tetrahydrobiopterin. Like folate contains pterin group

Question 46

Two entry points for aminos into urea cycle

Answer 46

Glutamate in mitochondria Cytosol as aspartate

Question 47

major site of glutamine catabolism

Answer 47

Kidney

Question 48

___ supplies nitrogen to urea cycle

Answer 48

glutamate,

Question 49

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

Answer 49

Carbamoyl phosphate synthetase reaction

Question 50

Urea cycle uses __ to activate bicarbonate unit

Answer 50

ATP

Question 51

What is the regulator of carbamoyl phosphate synthetase reaction?

Answer 51

N-acetyl-glutamate Inherent metabolic sensor

Question 52

How do you increase flux in urea cycle?

Answer 52

Increase intermediates by carbamoyl phosphate synthetase

Question 53

Cost of Urea cycle

Answer 53

4 ATP per Urea