Chapter 14b Flashcards
all species that can fix nitrogen contain the ______________
nitrogen complex
the nitrogenase complex consists of what two proteins?
nitrogenase and reductase
electrons from reduced ferredoxin –> reductase –> nitrogenase
reductase and nitrogenase are ________ proteins
iron sulfur proteins
what does reductase do?
it transfers electrons from ferredoxin to the nitrogenase
nitrogenase, aka MoFe protein does what?
what prosthetic groups does it use?
Catalyzes the reaction
N2 + 8H+ + 8e- 2NH3 + H2
P cluster and MoFe cofactor
what are the steps of the nitrogen cycle
- nitrogen fixation
- nitrification
- denitrification
- nitrogen assimilation
- deamination
Nitrogen balance
Positive: Nintake> Nloss; pregnancy, infants, recuperating patients
Negative: Nintake< Nloss; malnutrition, Kwashiorkor
_______ reactions dominate amino acid metabolism
transamination
this is catalyzed by aminotransferases or transaminases
alpha amino acid is a ________
alpha keto acid is ___________-
alpha amina acid is DONOR
alpha keto acid is RECEPTOR
What enzyme does transamination reactions require
PLP
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 (___________)
double displacement reaction
ammonium ion is incorporated into an amino acid through glutamate and glutamine
________________ enzyme catalyzes the incorporation of ammonia into alph ketoglutarate to generate glutamate
glutamate dehydrogenase
______________ incorporates another nitrogen into glutamate in an amidation reaction to form glutamine
glutamine synthetase
The carbon skeletons for amino acid sythesis are provided by intermediates of the ___________,____________,_____________–
glycolytic pathway, CAC, pentose phosphate pathway
transamination reactions are catalyzed by ___________. these enzymes require the coenzyme pyriodoxal phosphate, which is derived from pyridoxine
transaminases (aminotransferases)
cystine goes into what metabolism?
sulfur metabolism
serine makes what?
ethanolamine and sphingosine
glycine, cysteine
glycine goes into what pathways?
purine, porphyrin and glutathione synthetic pathways
the synthesis of glycine requires the cofactor__________-
tetrahydrofolate
______________ is a B vitamin whose structure consists of a pteridine nucleus and para-aminobenzoic acid linked to one or more glutamic acid residues
Folic Acid
once absorbed by the body, folic acid is converted to THF
Methionine is regenerated from homocysteine by the methylcobalamin-dependent enzyme _______________, which catalyzes the transfer of a carbon from N5-methyltetrahydrofolate.
methionine synthase
After donation of a methyl group by S-adenosylmethionine, the resulting S-adenosylhomocysteine is cleaved to yield ________ and ________
adensosine
hoomocysteine
most common reducing agent?
glutathione
The catecholamines includes;
dopamine
epinephrine
norepinphrine are derivatives of tyrosine
What are the amines of the following?:
glycine?
glutamate?
aminobutyric acid (GABA)?
glycine? norepinephrine
glutamate? epinephrine
aminobutyric acid (GABA)? dopamine, serotinin, histamine
waht is the key enzyme in pyrimidine synthesis?
aspartate transcarbamolyase
orotate reacts with activated ribose in form of _____________ to form orotidylate
PRPP
PRPP is syntehsized from ribose 5-phosphate and ATP by PRPP synthease
uridine monophophate is generated by the decarboxylation of orotidylate by _______________–
orotidylate decarboxylate
nucleoside monophophates are converted into diphophates by specific ___________ for instance, UMP kinase forms UDP from UMP
nucleoside monophophate kinases
_____________, which have broad specificity, catalyze the interconversion of di-and triphophates
nucleoside diphosphate kinases
CTP is formed from UTP by the replacement of a carbonyl group with an amino group. glutamine provides the amino group
CTP synthetase
thymine a product of DNA degradation, is salvaged by first being incorporated into a nucleoside by _____________
__________ is then generates the nucleotide
thymidine phosphorylase
thymidine kinase
Purine reaction is catalyzed by _____________-
glutamine phosphoribosyl amidotransferase
the immediate source of electrons for the reduction of the reductase is ____________-
thioredoxin
