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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