Prescott’s Microbiology, 9th Edition
Chapter 11 – Catabolism: Energy Release and Conservation
GUIDELINES FOR ANSWERING THE MICRO INQUIRY QUESTIONS
Figure 11.4 Is NAD+ reduced to NADH in the catabolic or anabolic direction of this pathway?
The catabolic direction of the EMP will oxidize glucose and reduce NAD+ to NADH.
Figure 11.5 Which reactions are examples of substrate-level phosphorylation?
Steps 6 and 9 in the process. Step 6 is transferal of a phosphate from 1,3-bisphosphoglycerate to
ADP, and step 9 is transferal of a phosphate from phosphoenolpyruvate to ADP.
Figure 11.6 For what kinds of reactions is NADPH used?
In general, NADH is used in catabolic reactions and NADPH is used in anabolic reactions.
Figure 11.7 For what macromolecule is ribose 5-phosphate a precursor?
Ribose is part of nucleotides, thus it is a precursor of DNA and RNA.
Figure 11.8 What reaction provides the energy to fuel the condensation (joining) of the 4-carbon
oxaloacetate with the 2-carbon acetyl-CoA to form citrate?
The pyruvate dehydrogenase complex (PDH) catalyzes step one in this figure. Hydrolysis of the
thioester bond in acetyl-CoA is sufficient to drive the condensation between it and oxaloacetate
(as stated in the description next to the number 1 in the figure).
Figure 11.12 How does the number of H+ moved across the membrane as a result of NADH
oxidation compare with the number of H+ moved following methanol oxidation?
NADH oxidation results in three protons transported, with all three protein complexes involved.
Methanol only involves the last complex, and thus only transports one proton.
Figure 11.19 How many NADH are reoxidized to NAD+ for each glucose metabolized?
Looking at the EMP pathway in figure 11.5, two NADH are generated for each molecule of
glucose oxidized to two pyruvate. As the two pyruvate go through fermentation, both of the
NADH are reoxidized to NAD+, so the net effect is cancelled out.
Figure 11.21 What is the difference between a hydrolase and phosphorylase?
A hydrolase is an enzyme that catalyzes the hydrolysis of a chemical bond (via addition of water)
while a phosphorylase is an enzyme that catalyze the addition of a phosphate group from an
inorganic phosphate to an acceptor. From the reactions, one can see that the enzymes maltase,
sucrose, and beta-galactosidase are all hydrolases, while the phosphorylase enzymes all have that
term in their name.
Figure 11.23 Why are fatty acids a rich source of energy even though no ATP is generated when
they are degraded by the beta-oxidation pathway?
Fatty acids are very reduced, thus great energy sources in cells (also an excellent carbon source).
Oxidation generates NADH and FADH2, which can then be used to generate ATP in the ETC.
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Prescott’s Microbiology, 9th Edition
Figure 11.31 When electrons from P700 are used to reduced NADP+, what compound supplies
electrons for the re-reduction of P700?
When electrons from P700 are used to reduce NADP+ the electrons cannot be recycled to reduce
oxidized P700 so photosystem II participation is required. It donates electrons to oxidized P700
and generates ATP in the process. Electrons subsequently travel to the plastoquinone pool and
down an ETC to reduce P700.
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© 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in
any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part.