ch 12 anabolism: the use of energy in biosynthesis Flashcards

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1
Q

where does the calvin cycle occur?

A

in eukaryotes - stroma of chloroplasts
in cyanobacteria - some nitrifying bacteria and thiobacilli, may occur in carboxysomes

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2
Q

3 phases of calvin cycle

A

carboxylation phase
reduction phase
regeneration phase
3 ATP and 2NADPH are used during the incorporation of 1 CO2

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3
Q

carboxylation phase

A

enzyme ribulose 1,5-biphosphate carboxylase/oxygenase (RuBisCO) catalyzes the addition of CO2 to the 5-carbon molecules RuBP forming a 6-carbon intermediate that rapidly and spontaneously splits into two molecules of PGA

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4
Q

reductive TCA cycle

A

alternative CO2 fixation pathway used by some autotrophs in the bacterial phyla aquificota, proteobacteria, nitrospirota, bacteroidata

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5
Q

gluconeogenesis

A

synthesis of glucose-6-phosphate from noncarbohydrate precursors
shares enzymes with EMP
3 reactions catalyzed by 3 enzymes

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6
Q

peptidoglycan synthesis

A

complex process involving UDP derivatives
bactoprenol phosphate used to transport NAG-NAM-pentapeptide units across cell membrane
final step, transpeptidation, creates cross-links btw the stem peptides on the peptidoglycan strand

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7
Q

two ways ammonia is incorporated into the carbon skeleton

A
  • reductive amination pathway: forms glutamate from alpha-ketoglutarate, catalyzed by glutamate dehydrogenase when ammonia conc is high, once glutamate has been synthesized the newly formed amino group can be transferred by transaminases to other carbon skeletons
  • glutamine synthetase-glutamate synthase system: assimilate ammonia when levels are low, carboxyl group found in side chain of glutamate reacts with ammonia, and the incorporated nitrogen exists as amide in glutamine, then transfers to generate two glutamate molecules
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8
Q

assimilatory nitrate reduction

A

used by bacteria to reduce nitrate to ammonia and the incorporate it into an organic form
nitrate reduction to nitrite catalyzed by nitrate reductase
- nitrite toxic to those without nitrite reductase (most eukaryotes)

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9
Q

nitrogen fixation

A

the reduction of atmospheric gaseous nitrogen to ammonia
catalyzed by nitrogenase - requires a large ATP expenditure
- only carried out by a few bacteria and archaea (diazotrophs)

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10
Q

assimilatory sulfate reduction

A

reduction of sulfate to sulfide then to hydrogen sulfide
sulfur needed for:
- synthesis of amino acids
- synthesis of several coenzymes
sulfur obtained from:
- either external source or intracellular amino acid reserves
- inorganic sulfate

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11
Q

anaplerotic reactions

A

reactions that replenish depleted tricarboxylic acid cycle intermediates

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12
Q

glyoxylate cycle

A

functions is some bacteria, fungi, and protists
need two enzymes: isocitrate lyase and malate synthase
modified TCA cycle - convert acetyl-CoA to oxaloacetate without the loss of the acetyl-coa carbons as CO2

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13
Q

most common phosphorus sources

A

inorganic phosphate and organic molecules with a phosphoryl group

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14
Q

phosphatases

A

hydrolyze organic phosphate-containing molecules to release inorganic phosphate
gram-negative bacteria have them in the periplasmic space, which allows phosphate to be taken up immediately after release
protists can directly use organic phosphates after ingestion of hydrolyze them in lysosomes and the incorporate the phosphate

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15
Q

purine biosynthesis

A

complex pathway in which seven different molecules contribute parts to the final purine skeleton
- initial products are ribonucleotides
deoxyribonucleotides formed by reduction of nucleoside diphosphates or nucleoside triphosphates

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16
Q

pyrimidine biosynthesis

A

begins with the carbon skeleton of aspartic acid and additional carbon and nitrogen atoms derived from bicarbonate and glutamine
- construction of pyrimidine ring is completed before ribose is attached

17
Q

fatty acid biosynthesis

A

synthesized from acetyl-coa, malonyl-coa, NADPH by fatty acid synthase complex
intermediates are attached to the acyl carrier protein
double bonds can be added either by using NADPH and O2 or by dehydrating hydroxy fatty acids

18
Q

sterols and isoprenoid lipids

A

sterols found in eukaryotic membranes
isoprenoid lipids (isoprenes) found in archaeal membranes
isoprenes made from two sterol pathway intermediates

19
Q

lipopolysaccharides

A

important component of the outer membrane of typical gram-negative bacteria
combines lipid and carbohydrate anabolic pathways
lipid-a core branch and o-antigen branch
current model suggest seven proteins (Lpt proteins) forms a path along which LPS moves from the plasma membrane across the aqueous periplasm