Exam 15: Biosynthesis

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Molecules with varying numbers of carbon...

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A) special thick-walled cells (heterocysts) in filamentous cyanobacteria, such as Anabaena
B) special nitrogenase-protecting proteins in Azotobacter species
C) temporal separation of nitrogen fixation (at night) and photosynthesis (during the day) in some species of cyanobacteria
D) growth under aerobic conditions
E) growth under anaerobic conditions

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A) NH3
B) N₂
C) HN=NH
D) H₂N-NH₂
E) NADPH

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Modular enzymes consist of multiple modu...

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A) $\mathrm{CO}_{2}+$ ribulose 1,5 -bisphosphate $\rightarrow 2,3$ -phosphoglycerate
B) $\mathrm{HCO}_{3}{ }^{-}+$ acetyl-CoA $\rightarrow$ malonyl-CoA + NADPH $\triangle 3$ -hydroxypropionate
C) $\mathrm{H}_{2} \mathrm{~S}+$ light $\rightarrow \mathrm{S}^{0}+2 \mathrm{H}^{+}+2 \mathrm{e}^{-}$
D) Ribulose-1,5-bisphosphate $+\mathrm{CO}_{2}{ }^{-} \rightarrow$ Fructose- 1,6 -bisphosphate
E) 2-carboxy-3-ketoarabinitol-1,5-bisphosphate $\rightarrow$ G3P

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A) It involves successive condensations of malonyl-ACP.
B) A dehydratase is used to generate an unsaturated bond.
C) It is regulated by the stringent response of carbon starvation.
D) NADPH is generally involved in hydrogenation.
E) Many single-component enzymes are involved.

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A) organotrophs and iron oxidizers
B) photoheterotrophs and chemiolithotrophs
C) photoautotrophs and lithotrophs
D) heterotrophs and methanogens
E) methanogens and photoheterotrophs

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A) Several different transport mechanisms are used for $\mathrm{CO}_{2}$ and $\mathrm{HCO}_{3}-$ .
B) $\mathrm{CO}_{2}$ and $\mathrm{HCO}_{3}^{-}$ are sequestered inside a carboxysome.
C) Rubisco is sequestered inside a carboxysome.
D) Carbonic anhydrase is used to convert $\mathrm{CO}_{2}$ to $\mathrm{HCO}_{3}^{-}{ }^{-}$ and thus trap it.
E) Proteins are used to block light and thus the light reactions.

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Because fatty acid biosynthesis consumes...

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A) the large subunit.
B) the small subunit.
C) a cavity that forms between an LSU and an SSU.
D) the chloroplast.
E) the chlorosome.

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A) conversion of nitrate or nitrite to N₂ by anaerobic respirers.
B) oxidation of NH4+ to nitrate or nitrite by lithotrophs.
C) conversion of N₂ to NH4+.
D) removal of nitro groups from organic molecules.
E) removal of amino groups from organic molecules.

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A) amino acids; diatom; bacterium
B) fixed nitrogen; diatom; bacterium
C) fixed nitrogen; bacterium; diatom
D) vitamin B12; diatom; bacterium
E) vitamin B12; bacterium; diatom

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A) cytochrome
B) chlorophyll
C) vitamin B12
D) tryptophan
E) hemoglobin

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A) tryptophan
B) tyrosine
C) phenylalanine
D) leucine
E) isoleucine

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A) amino acids
B) nucleotides
C) fatty acids
D) tetrapyrrole
E) nonribosomal peptide antibiotics

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A) Different oxidation states of nitrogen require different amounts of reducing energy.
B) It is easy for living organisms to assimilate nitrogen due to its great stability.
C) Nitrogen forms must be fully reduced to NH3.
D) Only bacteria and archaea can assimilate elemental nitrogen.
E) It is expensive, requiring reducing energy and ATP.

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A) 3-phosphoglycerate synthetase; added to another carbon dioxide
B) 3-phosphoglycerate synthetase; reduced to glyceraldehyde-3-phosphate
C) nitrogenase; reduced to glyceraldehyde-3-phosphate
D) Rubisco; reduced to glyceraldehyde-3-phosphate
E) Rubisco; added to another carbon dioxide

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A) reverse TCA cycle.
B) 3-hydroxypropionate cycle.
C) Calvin cycle.
D) reductive acetyl-CoA pathway.
E) glyoxylate bypass.

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