microbiology chapter 6
Please select the FALSE statement regarding the central metabolic pathways:
The transition step and TCA cycle are repeated four times to yield ATP, reducing power, and three different precursor metabolites.
Why would a cell ferment rather than respire?
There is no oxygen present and it cannot use anaerobic respiration OR it lacks the ability to respire (i.e., no electron transport chain).
Which is (are) true of coenzymes?
They are organic molecules. They transfer atoms from one molecule to another. They may bind to a number of different enzymes. They are synthesized from vitamins.
Which is (are) true regarding organic acids?
They are weak acids. They are often involved in metabolic reactions. They often exist in the ionized form at the near-neutral pH found in a cell. Pyruvate and pyruvic acid refer to different forms of the same substance.
Which is true regarding the three central metabolic pathways?
They form high-energy bonds that can be used to synthesize ATP. They form intermediates that can be oxidized to generate reducing power. They form precursor metabolites.
H2S and NH3 may be used by some prokaryotes as energy sources.
True
In fermentation, the only ATP produced was during glycolysis and the fermentation reactions usually result in converting NADH to NAD.
True
True or False? Both glycolysis and pentose phosphate pathway oxidize glucose to pyruvate.
True
True or False? Cells must secrete enzymes the degrade macromolecules into their subunits before they can use these compounds.
True
True or False? The TCA cycle must "turn twice" in order to complete the oxidation of one glucose molecule.
True
Oxygen serves as the terminal electron acceptor in
aerobic respiration
Biosynthetic reactions that require energy for the conversion of molecular subunits into larger molecules are called
anabolic
The linking of N-acetyleglucosamine, N-acetylemuramic acid, and tetrapeptides is a(n) ______ reaction that ______ ATP.
anabolic; requires
Most enzymes
are specific, typically recognizing a single or a few substrates.
The term "precursor metabolite" refers to molecules that
are used in biosynthesis
Mercury in mercurochrome inhibits growth
by oxidizing the sulfhydryl groups in cysteine AND by changing the shape of proteins.
Enzymes act as
catalysts
The small, non-protein molecules that can be readily separated from an enzyme and are responsible for transfer of atoms from one molecule to another are referred to as
coenzymes
The use of the suffix "ase" on a word denotes a(n)
enzyme
Studies done by Buchner showed that ground-up yeast cells were able to convert sugar to alcohol. The components of the mixture that were responsible for this transformation were
enzymes
True or False: The Calvin cycle produces six ATP for every six turns of the cycle.
false
True or false: Competitive inhibition usually involves both substrate and inhibitor competing for binding at the allosteric site.
false
Pyruvate can be metabolized along two major routes. They are:
fermentation and respiration
Fermentation is sometimes used as a means of slowing food spoilage. Why would fermentation lead to this outcome?
fermentation will lead to the production of acidic by-products, dropping the pH of the food below a level that bacteria can tolerate
Cells degrade sugar largely to
gain energy
The most common starting pathway for the breakdown of sugars is
glycolysis
Allosteric enzymes
have an additional binding site that is involved in regulating enzyme activity
Your brother has a bacterial infection. He tells you he going to the gym where he plans to sit in the sauna for an hour. He thinks that this will cure his infection, because the heat in the sauna will denature the enzymes of the bacteria making him ill. You are a nursing student who is currently studying microbiology. You tell him that
his plan won't work; homeostasis will keep his body temperature constant even in the sauna, so the bacteria (and his normal microbiota and body cells) will not be impacted.
The electron transport chain is a group of membrane-embedded carriers that pass electrons from one to the next, while simultaneously pumping ______ across the membrane, generating a(n) ______.
hydrogen ions; proton motive force
The mutual interaction of substrate and enzyme is described as a(n)
induced fit.
Feedback inhibition
is a way of regulating the amount of product produced
Free energy:
is the amount of energy gained by breaking bonds of a chemical.
Proton motive force
is used to synthesize ATP
The energy yield of any energy-transforming pathway
is variable depending on the amount of precursor metabolites removed for biosynthesis
The transition step
links glycolysis to the TCA cycle.
Enzymes speed up reactions by
lowering the activation energy
Anoxygenic photosynthetic bacteria
may obtain electrons from H2S.
The general term used to describe the anabolic and catabolic reactions in a cell is
metabolism
An atom that has a lower affinity for electrons than another is ______ than the other.
more electronegative
Exergonic reactions:
occur when there is more free energy in the reactants than the products.
The name given to the reaction involving removal of electrons or hydrogen atoms from a compound is
oxidation
The terminal electron acceptor in respiration may be
oxygen, nitrate, OR an inorganic molecule
Bacteria that can absorb light energy and convert it into ATP are commonly called:
phototrophs
Glycolysis, the Entner-Duodoroff pathway, and the pentose phosphate pathway all produce:
pyruvate
The name given to the reaction involving addition of electrons or hydrogen atoms to a compound is termed
reduction
The electron transport system
requires a membrane AND generates a concentration gradient of protons.
Most enzymes function best at
slightly above pH 7 and low salt concentrations.
Which type of phosphorylation does not require a membrane?
substrate-level phosphorylation
Enzymes act on _______ to produce ________.
substrates, products
Environmental factors that may affect enzyme activity are
temperature, pH, AND salt.
Energy is defined as
the capacity to do work
What happens to the carbon molecules in the pyruvic acid that goes through the TCA cycle?
they become carbon dioxide
Which of the following produces the most precursor metabolites?
Glycolysis
Please identify the TRUE statement.
"Substrate" refers to a substance on which an enzyme acts to form products OR a surface on which an organism can grow.
Which is true of competitive inhibition?
A sulfa antibiotic is a competitive inhibitor.
The readily usable energy currency of cells is
ATP
Which enzyme drives ATP synthesis in respiration?
ATP synthase
Which of the following processes generates the greatest amount of energy?
Aerobic respiration
A worker in a cheese-making facility argued that whey, a nutrient-rich by-product of the process, should be dumped into a nearby pond to serve as fish food. Is this a good idea or a bad one, and why?
Bad idea- bacteria would thrive on this rich nutrient source and multiply, using the oxygen in the water to harvest the energy from the whey. Without the oxygen, the fish will die.
Chemolithotrophs near hydrothermal vents support a variety of life forms. Why is this analogous to photosynthetic microbes supporting life forms closer to the surface of the planet?
Because all life forms need some energy source, electron source, and carbon source. Chemolithotrophs fix inorganic carbon and, if consumed by other microbes, could serve as sources for all three requirements for life. This is very similar to the role that photosynthetic microbes play in the top levels of the oceans/lakes.
Please select the TRUE statement regarding metabolic processes.
Catabolic processes harvest the energy released during breakdown of compounds to synthesize ATP.
central metabolic pathways:
Glycolysis oxidizes glucose to pyruvate, yielding some ATP and NADH, and six different precursor metabolites. The pentose phosphate pathway oxidizes glucose, producing two different precursor metabolites and NADPH for biosynthesis. The transition step and TCA cycle complete the oxidation of glucose, yielding ATP, reducing power, and three different precursor metabolites.
Which pair is correctly matched, regarding electron transport carriers in eukaryotes?
Complex III - cytochrome bc1 complex
Heart muscle is damage after a heart attack (MI) because blood flow to the heart is stopped. A researcher injected cyanobacteria into the damaged hearts of test animals that have been given MIs. The animals conditions improved after the procedure, but not significantly. The researcher repeated the experiment, this time illuminating the cyanobacteria with high intensity light after injecting the cells into the damaged hearts. Now the animals did much better, recovering well from their heart attacks. Which of the following explains the outcome?
Cyanobacteria produce oxygen by photosynthesis. Illuminating the cells increases amount of O2 released that is then used by heart cells for aerobic respiration.
Which of the following is NOT common to aerobic respiration, anaerobic respiration, AND fermentation?
Electron transport chain
The TCA cycle produces
FADH2, NADH, and Precursor metabolites.
True or False: In Gram-negative bacteria, the electron transport chain involved in respiration is located in the lipopolysaccharide layer.
FALSE
True or False: The terminal electron acceptor in aerobic respiration is water, which is broken down to hydrogen and oxygen.
FALSE
The change in free energy of a reaction varies
False
True or False? Enzymes are changed by the reaction as they raise the activation energy
False
What is the effect of poisons such as mercury in antimicrobial products? Recall that mercury oxidizes the S-H groups of the amino acid cysteine in proteins, converting it to cystine.
Irreversible non-competitive inhibition- the mercury binds to an allosteric site on the enzyme and permanently changes the shape of the active site, so that the enzyme becomes nonfunctional.
Glycolysis:
It yields ATP. It is an anaerobic process. It occurs during fermentation. ATP is used.
NAD in its reduced form is symbolized as
NADH
In the electron transport system:
NADH donates electrons "upstream" of where FADH2 donates electrons.
A student argued that aerobic and anaerobic respiration should produce the same amount of energy. He argued that both processes are essentially the same—only the terminal electron acceptor is different. What's wrong with his argument?
Not all electron acceptors are the same—some are closer in terms of electronegativity to their high-energy electron carrier molecules (e.g., NADH) than others, and this impacts the amount of produced energy. Oxygen has the highest electron affinity of the terminal electron acceptors used.
Experiments designed by ______ suggested that living cells caused the fermentation of sugar to produce alcohol.
Pasteur
True or False: The production of ATP via the electron transport system, in either eukaryotes or prokaryotes, requires the use of a membrane.
TRUE
How would cellulose-degrading bacteria in the rumen (stomachs) of a cow benefit the animal?
The bacteria would produce, secrete, and incorporate organic molecules as they obtain energy from the cellulose in grass and replicate. The cow could then digest both the secreted organic molecules AND the bacteria that synthesized them.
Which is FALSE regarding glycolysis?
The end product is acetyl-CoA.
Which of the statements about catabolism and anabolism is TRUE?
The energy gathered during catabolism is used during anabolism
Each of the following statements about chemoorganotrophs is true EXCEPT they may use substrate-level phosphorylation to produce ATP. they may use oxidative phosphorylation to produce ATP. they may use photophosphorylation to produce ATP. they obtain energy by degrading organic compounds. they generally rely on the metabolic activities of photosynthetic organisms.
they may use photophosphorylation to produce ATP.
Degradation of fats as an energy source involves all of the following except
transamination
Glycolysis may occur:
under aerobic or anaerobic conditions.
Fermentation:
uses an organic molecule as the final electron acceptor.
Coenzymes are derivatives of
vitamins
In the phototrophic production of energy, the oxygen originates from
water
