Bacterial Metabolism Flashcards
T/F In general, bacterial cells have the same metabolic activities as eukaryotic cells?
T
glycolysis review: how many moles ATP consumed vs. how many produced per mole glucose?
2 consumed, 4 produced per mole of glucose in glycolysis
describe the glyoxylate shunt
functions similarly to the Krebs cycle but lacks some of the Krebs enzymes. consumes acetyl CoA. Basically a simplified version of the Krebs cycle with a shortcut.
can some bacterial perform aerobic respiration/oxydative phos without the presence of oxygen?
YES, some bacterial can do aerobic respiration using a terminal electron acceptor other than oxygen (ie, NO3- which is nitrate and turns to N2, nitrogen gas)
what happens if the ETC/TCA get backed up (due to lack of oxygen, for example?)
some of pyruvic acid formed from glucose during glycolysis is reduced using NADH: this regenerates NAD+
How is ATP synthesized during fermentation?
via substrate-level phosphorylation only.
aerobic respiration v fermentation: what are the relative levels of energy released?
much more energy released by respiration than by fermentation (on the order of 10x)
describe obligate aerobes.
O2 is absolutely necessary for the growth of these organisms. they do not have the enzymes needed for fermentation. can’t ferment. can only respire.
describe facultative anaerobes.
grow under aerobic and anerobic conditions. they grow better aerobically than anaerobically. may do both at the same site. contain a functional respiratory system and also have fermentative capacity.
describe obligate anaerobes.
can gain energy only from fermentation mechanisms; do not possess cytochromes or an ETC. cannot grow in the presence of 02.
what do obligate anaerobes produce on exposure to 02? how does this occur?
hydrogen peroxide – created because they contain flavins that produce peroxide when O2 is around. ROS from H202 can damage DNA and proteins.
describe catalase. do anaerobes contain it? aerobes?
obligate anaerobes lack catalase, which is an enzyme which decomposes H202. Most aerobes contain catalase.
describe superoxide dismutase.
highly reactive, free radical reactive form of oxygen (02-) formed by flavoenzymes. breaks down superoxide.
describe aerotolerant anaerobes
grow exclusively via fermentation, but are indifferent to oxygen and can grow in air. do not have resp system, are not capable of oxidative phosphorylation.
describe microaerophiles
organisms that will tolerate oxygen only if it is at a lower concentration than found in air (5% rather than 20%). require special growth conditions to culture.
where do anaerobes exist within a host?
anaerobic conditions exist in mouth or urinary tract – can grow in tissue we usually think of as aerated, because other bacteria are present OR host is using up all the air.
what do most microbes use as a growth substrate?
glucose
glucose is a monosaccharide or disaccharide? what about lactose?
gluc: mono. lactose: disaccharide, requires cleavage by a glactosidase prior to catabolism
name organisms that can use either glucose or lactose as a substrate (3)
E coli, Klebsiella, citrobacter
organisms that can use glucose as a substrate but NOT lactose (2)
salmonella, shingella
organisms that cannot use glucose or lactose as a growth substrate (1)
pseudomonas
which types of aerobes have catalase and superoxide dismutase?
obligate aerobes, facultative anaerobes. NOT obligate anaerobes.
glucose to CO2 and H2O: oxidation or reduction?
oxidation, because glucose is losing H. oxidizes to pyruvate.
during which process do the bacteria make ATP via substrate level phosphorylation?
glycolysis
during which process do the bacteria make ATP via oxidative phosphorylation?
electron transport chain.
besides generating ATP, what can the electron gradient be used for?
cellular motility, and also pumping out/efflux of antibiotics.
describe what happens to NAD/NADH and FADH/FADH2 in glycolysis and fermentation
Glycolysis generates reduced species (NADH and FADH2) and Fermentation recycles them so that glycolysis can take place again. Glycolysis: NAD+ -> NADH, FADH -> FADH2.
Fermentation: NADH -> NAD+.
name 2 common products of fermentation
lactic acid, ethanol. NOT pyruvate, since pyruvate is the result of glycolysis.
how can lactic acid production affect the host human?
resulting low pH discourages growth of competing organisms. ie, in vagina, low pH environment protects against yeast.
how does the formation of butyric acid affect the host?
has very unpleasant odor, can be diagnostic. can be protective against intestinal pathogens such as E Coli.
how does the formation of propionic acid affect the host?
will ferment lactate to acetic acid, Co2, and propionic acid. used in manufacture of Swiss cheese. thought to be pathogenic -> acne.
describe mixed acid fermentations
generally used by enteric microbes (intestinal) because 02 is limited so need to do fermentation. mixed products can include H2, formic acid, acetic acid, succinic acid.
