Entner-Doudoroff pathway is found in
Answer: C
Correct answer: both (a) and (b)
The Entner-Doudoroff pathway is found in prokaryotes of both kinds - aerobes such as Pseudomonas and anaerobes such as Zymomonas. It is an alternative to glycolysis, yielding only 1 ATP per glucose instead of 2, and it is essentially absent from eukaryotes.
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The role of bacteriochlorophyll in anoxygenic photosynthesis is to
Answer: C
Correct answer: use light energy to energize an electron
A bacteriochlorophyll molecule in the reaction centre absorbs a photon and is raised to an excited state, from which it donates a high-energy electron to the first acceptor. Everything else - the transport chain, the proton gradient, the ATP - follows from that single act of energising an electron.
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Nitrogen fixation is a process that requires
Answer: C
Correct answer: both (a) and (b)
Nitrogen fixation needs both. It is enormously expensive in energy - some 16 ATP per N2 reduced - because the triple bond is so strong. And nitrogenase is irreversibly inactivated by oxygen, so the reaction must take place in an anaerobic setting: a heterocyst, a root nodule protected by leghaemoglobin, or an anaerobic habitat.
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Dolichol phosphate is
Answer: B
Correct answer: the anchor on which sugars assemble before transfer to proteins
Dolichol phosphate is a long polyisoprenoid lipid embedded in the ER membrane. The core oligosaccharide of an N-linked glycoprotein is built up on it, sugar by sugar, and then transferred as a block to an asparagine residue of the growing protein.
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Which of the following catalyze liberation of orthophosphate from organic P compounds and inorganic pyrophosphate ?
Answer: A
Correct answer: Alkaline phosphatase
Alkaline phosphatase hydrolyses phosphate esters and inorganic pyrophosphate, releasing free orthophosphate, and works best at alkaline pH. Bacteria induce it when phosphate is scarce, so that organic sources can be scavenged.
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Phosphate is considered to restrict the induction of
Answer: B
Correct answer: secondary metabolites
Phosphate at growth-supporting concentrations represses secondary metabolism - antibiotics, alkaloids, pigments - while primary metabolism, which the cell needs to grow, proceeds. This is why industrial fermentations are often run with phosphate deliberately limited once growth is complete.
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Catabolism is a form of metabolism in which _____molecules are converted into ________molecules.
Answer: A
Correct answer: large, small
Catabolism degrades: large molecules are broken into small ones, and the energy released is captured as ATP. It is the source of both the energy and the precursors that anabolism goes on to spend.
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If ΔG of a chemical reaction has a negative value, the reaction
Answer: A
Correct answer: releases energy
A negative \(\Delta G\) means the products hold less free energy than the reactants, so the reaction is exergonic and proceeds spontaneously in that direction. A positive \(\Delta G\) marks an endergonic reaction, which will run only if coupled to one that releases more.
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The acquisition of energy by glucose fermentation requires
Answer: A
Correct answer: substrate-level phosphorylation
Fermentation has no electron transport chain and no external electron acceptor, so all its ATP comes from substrate-level phosphorylation - a phosphate group transferred directly from a high-energy intermediate such as 1,3-bisphosphoglycerate or phosphoenolpyruvate to ADP. That is why the yield is only 2 ATP per glucose.
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Unlike active transport, passive and facilitated diffusion do not require
Answer: A
Correct answer: all of these
Passive and facilitated diffusion both move solute down its electrochemical gradient, so they need none of the three: no metabolic energy, and no ability to concentrate or accumulate solute against a gradient. Facilitated diffusion differs from simple diffusion only in using a carrier protein, which makes it faster and specific but no less passive. Doing any of these things is what defines active transport.
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