Chapter 14b

Question 1

all species that can fix nitrogen contain the ______________

Answer 1

nitrogen complex

Question 2

the nitrogenase complex consists of what two proteins?

Answer 2

nitrogenase and reductase

electrons from reduced ferredoxin –> reductase –> nitrogenase

Question 3

reductase and nitrogenase are ________ proteins

Answer 3

iron sulfur proteins

Question 4

what does reductase do?

Answer 4

it transfers electrons from ferredoxin to the nitrogenase

Question 5

nitrogenase, aka MoFe protein does what?

what prosthetic groups does it use?

Answer 5

Catalyzes the reaction
N2 + 8H+ + 8e-  2NH3 + H2

P cluster and MoFe cofactor

Question 6

what are the steps of the nitrogen cycle

Answer 6

• nitrogen fixation
• nitrification
• denitrification
• nitrogen assimilation
• deamination

Question 7

Nitrogen balance

Answer 7

Positive: Nintake> Nloss; pregnancy, infants, recuperating patients

Negative: Nintake< Nloss; malnutrition, Kwashiorkor

Question 8

_______ reactions dominate amino acid metabolism

Answer 8

transamination

this is catalyzed by aminotransferases or transaminases

Question 9

alpha amino acid is a ________

alpha keto acid is ___________-

Answer 9

alpha amina acid is DONOR

alpha keto acid is RECEPTOR

Question 10

What enzyme does transamination reactions require

Answer 10

PLP

Question 11

With donation of a proton from a general acid and subsequent hydrolysis, the newly formed alpha keto acid is released

the reverse then occurs when a second alpha keto acid replaces the first (___________)

Answer 11

double displacement reaction

Question 12

ammonium ion is incorporated into an amino acid through glutamate and glutamine

________________ enzyme catalyzes the incorporation of ammonia into alph ketoglutarate to generate glutamate

Answer 12

glutamate dehydrogenase

Question 13

______________ incorporates another nitrogen into glutamate in an amidation reaction to form glutamine

Answer 13

glutamine synthetase

Question 14

The carbon skeletons for amino acid sythesis are provided by intermediates of the ___________,____________,_____________–

Answer 14

glycolytic pathway, CAC, pentose phosphate pathway

Question 15

transamination reactions are catalyzed by ___________. these enzymes require the coenzyme pyriodoxal phosphate, which is derived from pyridoxine

Answer 15

transaminases (aminotransferases)

Question 16

cystine goes into what metabolism?

Answer 16

sulfur metabolism

Question 17

serine makes what?

Answer 17

ethanolamine and sphingosine

glycine, cysteine

Question 18

glycine goes into what pathways?

Answer 18

purine, porphyrin and glutathione synthetic pathways

Question 19

the synthesis of glycine requires the cofactor__________-

Answer 19

tetrahydrofolate

Question 20

______________ is a B vitamin whose structure consists of a pteridine nucleus and para-aminobenzoic acid linked to one or more glutamic acid residues

Answer 20

Folic Acid

once absorbed by the body, folic acid is converted to THF

Question 21

Methionine is regenerated from homocysteine by the methylcobalamin-dependent enzyme _______________, which catalyzes the transfer of a carbon from N5-methyltetrahydrofolate.

Answer 21

methionine synthase

Question 22

After donation of a methyl group by S-adenosylmethionine, the resulting S-adenosylhomocysteine is cleaved to yield ________ and ________

Answer 22

adensosine

hoomocysteine

Question 23

most common reducing agent?

Answer 23

glutathione

Question 24

The catecholamines includes;

Answer 24

dopamine
epinephrine
norepinphrine are derivatives of tyrosine

Question 25

What are the amines of the following?:

glycine?
glutamate?
aminobutyric acid (GABA)?

Answer 25

glycine? norepinephrine
glutamate? epinephrine
aminobutyric acid (GABA)? dopamine, serotinin, histamine

Question 26

waht is the key enzyme in pyrimidine synthesis?

Answer 26

aspartate transcarbamolyase

Question 27

orotate reacts with activated ribose in form of _____________ to form orotidylate

Answer 27

PRPP

PRPP is syntehsized from ribose 5-phosphate and ATP by PRPP synthease

Question 28

uridine monophophate is generated by the decarboxylation of orotidylate by _______________–

Answer 28

orotidylate decarboxylate

Question 29

nucleoside monophophates are converted into diphophates by specific ___________ for instance, UMP kinase forms UDP from UMP

Answer 29

nucleoside monophophate kinases

Question 30

_____________, which have broad specificity, catalyze the interconversion of di-and triphophates

Answer 30

nucleoside diphosphate kinases

Question 31

CTP is formed from UTP by the replacement of a carbonyl group with an amino group. glutamine provides the amino group

Answer 31

CTP synthetase

Question 32

thymine a product of DNA degradation, is salvaged by first being incorporated into a nucleoside by _____________

__________ is then generates the nucleotide

Answer 32

thymidine phosphorylase

thymidine kinase

Question 33

Purine reaction is catalyzed by _____________-

Answer 33

glutamine phosphoribosyl amidotransferase

Question 34

the immediate source of electrons for the reduction of the reductase is ____________-

Answer 34

thioredoxin