Exam 15: Biosynthesis

Correct Answer

verified

The full Calvin cycle is only found in b...

View Answer

Show Answer

A) NADH
B) NADPH
C) ferredoxin
D) H₂
E) O₂

Correct Answer

verified

Show Answer

Correct Answer

verified

The assimilable ammonium ion (NH₄⁺) is p...

View Answer

Show Answer

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

Correct Answer

verified

Show Answer

Correct Answer

verified

The reductive acetyl-CoA pathway seems to be the most ancient CO₂ fixation and biomass assimilation; for example, in methanogens, up to 5% of the CO₂ they absorb is used in biosynthesis. It consists in the formation of an acetyl group using two CO₂ molecules converging from two different pathways. Formate is produced by reduction of CO₂ and transfer to tetrahydrofolate (THF), thus forming a C1 unit. The C1 unit is reduced to a methyl group, -CH₃. In methanogens, methane is formed from this C1 unit for energy gain. The methyl group can be fixed into biomass after being transferred to a tetrapyrrole (called TB and related to vitamin B₁₂). The second CO₂ molecule becomes \( \mathrm{CO}_{3}^{-} \) via carbon dioxide dehydrogenase \( \mathrm{CO}_{3}^{-} \). is condensed with coenzyme A and the methyl group carried by TB to form acetyl-CoA.

Correct Answer

verified

An operon (nifHDKTY) encodes the nitroge...

View Answer

Show Answer

A) phosphorous.
B) reduction.
C) energy.
D) carbon.
E) nitrogen gas.

Correct Answer

verified

Show Answer

A) One G3P is produced by everything three turns of the cycle.
B) Two molecules of G3P condense to form a six-carbon sugar.
C) One more G3P condenses with a sugar to form a larger molecule used for biosynthesis.
D) PGA is reduced to G3P after the PGA moves out of the carboxysome.
E) G3P is reoxidized to carbon dioxide so that the cycle continues.

Correct Answer

verified

E

A) fatty acids.
B) polyketide antibiotics
C) purines and pyrimidines
D) aromatic amino acids
E) tetrapyrroles

Correct Answer

verified

Show Answer

A) photosynthesis in which H₂S is the electron source
B) photosynthesis in which water photolysis produces H⁺, e^-, and O₂
C) bacteriorhodopsin-based photosynthesis
D) being near the surface of a pond where more oxygen is available
E) possession of a variety of chlorophylls to absorb a wide range of wavelengths of light

Correct Answer

verified

Show Answer

A) carbon dioxide.
B) nitrogen.
C) nitrate.
D) ammonium.
E) FeMo protein.

Correct Answer

verified

Show Answer

Correct Answer

verified

With more "expensive" amino acids, more ...

View Answer

Show Answer

Correct Answer

verified

as condenses with acetyl-CoA to form m...

View Answer

Show Answer

A) O₂
B) CO₂
C) NH₄⁺
D) N₂
E) H₂

Correct Answer

verified

Show Answer

Correct Answer

verified

Because fatty acid biosynthesis consumes...

View Answer

Show Answer

Correct Answer

verified

Show Answer

A) intermediates in a pathway are regenerated.
B) nutrients are imported from the environment.
C) molecules targeted for breakdown are salvaged for anabolism.
D) the reactions are thermodynamically impossible.
E) large amounts of ATP are generated.

Correct Answer

verified

Show Answer

Correct Answer

verified

In natural environments most nitrogen sources are subject to competition from dissimilatory metabolism. Fertilizers contain nitrogen as NH₄⁺, which can leach from agricultural soils to bodies of water where it can be oxidized to nitrate and nitrite by lithotrophs, a process known as nitrification. Nitrites can combine with hemoglobin, rendering it incapable of taking up oxygen. When infants drink water with high nitrate content, they become ill with "blue baby" syndrome, as nitrate becomes nitrite in the digestive system.