Glossary of Microbiology: Chapter 10

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What is the primary cycle of Carbon assimilation used by autotrophic bacteria?
The Calvin-Benson Cycle
What is the role of NADPH in CO2 fixation?
NADPH acts as an electron donor
The generation of glyceraldehyde-3-phosphate from 3-phophoglycerate uses parts of what other pathway?
It is essentially a reversal of a portion of the glycolytic pathway (EMP) (except it uses NADP+ rather than NAD+)
The conversion of glyceraldehyde-3-phosphate to ribulose-5-phosphate uses parts of what other pathway?
Reverse PPP
What is the cost in ATP and NADPH to fix one CO2?
Cost: 3 ATP and 2 NADPH
What is gluconeogenesis and when would a cell engage in it?
Gluconeogenesis is the synthesis of of new glucose (from noncarbohydrate precursors). A cell would engage in it when it requires more glucose (i.e. a heterotroph)
Does gluconeogenesis require ATP and does it produce coenzymes?
Yes, it requires 2 ATP. No, it does not produce coenzymes.
Can you recognize the addition units for polysaccharide biosynthesis?
ADP- or UDP-glucose, UDP-galactose, adn UDP-glucuronic acid.
In assimilatory nitrate reduction, N is reduced to what level before it is incorporated into organic constituents in the cell in "primary amination" rxns?
N is reduced to an ammonium ion (NH4+) to be incorporated into organic constiuents.
What is the role of transaminases?
Transaminases catalyze the formation of several amino acids using the same AA as an amino group donor (they transfer the alpha-amino group to other carbon skeletons)
What enzyme complex is responsible for N fixation?
Nitrogenase (complex of MoFe protein and 1 or 2 Fe proteins)
What kinds of organisms can fix N?
Only prokaryotes have nitrogenase and can fix N (1. free-living bacteria, 2. symbiotic bacteria, and 3. cyanobacteria)
What is the role of the heterocyst and how does it insure the functionality of Nitrogenase?
The heterocyst protects nitrogenase from toxic O2. It has thick cell walls and employs cyclic (anoxygenic) photophosphorilation.
What is Leghemoglobin? Is it bacterial (Rhizobium) or plant (legume) in origin?
Leghemoglobin is a compound molecule that converts N2 to NH4+. It is part bacterial (from Rhizobium) and part plant (from legume) in origin.
Which metabolites of the central metabolic pathways are the substrates for AA biosynthesis (5 'Families' of AAs)?
(1)alpha-ketoglutarate, (2)Oxaloacetate, (3) Pyruvate, (4) 3-Phosphoglycerate, and (5) Erythrose-4-phosphate
Why are anaplerotic reactions required?
Anaplerotic reactions are required to replenish components of cyclical pathways (both catabolic and anabolic) (Pg. 210)
What is the Glyoxylate Cycle and when is it used?
The Glyoxylate Cycle is a modified TCA cycle in which the decarboxylation reactions are bypassed by the enzymes isocitrate lyase and malate synthatse; it is used to convert (2)acetyl-CoA to succinate and other matabolites (oxaloacetate). It is used in orgs using acetate as sole C source.
How does the pentapeptide formation on UDP-NAM differ from polypeptide formation in translation?
Pentapeptide formation on UDP-NAM is a strictly enzyme driven process, it does not occur on a ribosome or involve RNA
What is unique about the terminal two amino acids (UDP-NAM pentapeptide)?
They are 2 alanine residues: D-alanyl-D-alanine, in the form of a dipeptide
What is bactoprenol?
Bactoprenol is a 55-carbon alcohol tht attaches to NAM by a pyrophosphate group and moves peptidoglycan components through the hydrophobic membrane
What happens after the NAG is added to the bactoprenol-NAM-pentapeptide?
After NAG is added to the bactoprenol-NAM-pentapeptide the complex is translocated to the exterior of the membrane
What provides the energy for the glycosidic bond formed with the addition of the repeat unit to the peptidoglycan?
-PO4 bond is energy is used to add onto glycosidic backbone
What provides the energy for the peptide bond formed in the cross-linkage of adjacent glycosidic backbones in the PG?
The D-ananyl-D-alanine bond is cleaved and provides the energy for cross-linkage of adjacent glycosidic backbones.
What becomes of the bactoprenol after it donates a repeat unit?
The bactoprenol returns to the cytoplasm to do its job again after it donates a repeat unit.
Describe the centripetal growth of cell walls for Streptococci.
In Streptococci centripetal cell wall growth, there is usually only 1 to a few zones of growth; the cell wall lengthens along an equitorial band and a notch is formed; this notch pinches together (septation) and forms 2 daughter cells.
How does cell wall growth of Streptococci differ from growth of Gram-negative bacilli?
In cell wall growth for Gram-negative bacilli, many growth sites are scattered along the cylindrical portion of the rod (diffuse growth); the rod must lengthen then divide (by septation as with Step.)
What are autolysins?
Autolysins are enzymes that partially digest peptidoglycan in growing bacteria so that the peptidoglycan can be enlarged.

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