micro exam 4

From the standpoint of fermentative microorganisms, the crucial product in glycolysis is

ATP and regenerated NAD+; the fermentation products are waste products

During electron transport reactions

OH- accumulates on the inside of the membrane while H+ accumulates on the outside.

Since glucose, a hexose, is the major source of energy for most prokaryotes, why would they need to have pentose sugars available?

Pentose sugars are needed for nucleic acid synthesis.

A notorious biofilm former implicated in cystic fibrosis is

Pseudomonas aeruginosa.

How and why is tetrathionate broth made in a lab?

Tetrathionate broth is made by adding thiosulfate and a strong oxidant (iodine) to minimal media.

A population consists of

all of the individuals of one species in the same area.

Wild type Salmonella use the ttrA gene locus to use tetrathionate as ____.

an electron acceptor for anaerobic respiration

If you had 10 grams of glucose and fed it to non-reproducing cells in 3 different conditions: 1. Fermenting 2. Anaerobic respiration 3. Aerobic respiration Which condition would give you the most energy after 1 hour?

aerobic respiration

Most metabolic pathways are amphibolic, which means they ___.

are both anabolic and catabolic

Syntrophs

are organisms that accomplish the catabolism and degradation of a substance through a cooperative effort with one or more other microorganisms.

Five-carbon sugars are used in the

biosynthesis of DNA and RNA.

Microbial growth on the two-carbon acetate substrate invokes

both the citric acid and glyoxylate pathways.

Improperly functioning acyl carrier proteins (ACPs) would likely result in

death for a bacterium due to poor lipid bilayer integrity.

Which of the following is an example of a biofilm?

dental plaque

A monophyletic group is a group that

descended from one ancestor.

The diversity of microorganisms in culture collections is representative of the diversity of microorganisms found in nature

false

True or false: The proton motive force is most often generated by splitting of H2.

false

True or false: The terminating step of moving electrons onto oxygen releases additional ATP during aerobic metabolism not made during anaerobic growth.

false

Which metabolic strategy does NOT invoke the proton motive force for energy conservation?

fermentation

The metabolic diversity of photosynthetic bacteria stems from different

light-harvesting complexes, electron donors, and organic compounds they produce.

The Calvin Cycle and nitrogenase fixation are both ___.

methods to harvest cellular materials from the air, reductive processes, energy intensive

Aerobic respiration and anaerobic respiration will always use different ____.

terminal electron acceptors (TEA)

Based on the figure below, which compound listed has the highest standard reduction potential (Eo)?

tetrathionate

True or false: Organisms grown with CO2 as its sole carbon source must have energy in the form of ATP as well as reducing power.

true

Mixotrophs

use inorganic compounds for energy and organic compounds as a carbon source.

Chemolithotrophs

use inorganic electron donors and CO2 as a carbon source.

Chemotrophs

use inorganic or organic chemicals as energy sources.

Phototrophs

use light as an energy source and CO2 as a carbon source.

Heterotrophs

use organic carbon as their carbon source.

Gluconeogenesis is the process of synthesizing __________.

glucose from other compounds

The Embden-Meyerhof-Parnas pathway is another name for

glycolysis.

Culture-independent approaches avoid issues associated with

growing organisms in the lab.

The net gain of ATP per molecule of glucose fermented is

2

You identify the prokaryotic cells you've found as a species of bacteria. These bacteria appear to be living off of nutrients and sulfur compounds released from the vents on the sea floor. Over time, the bacteria must have evolved extreme metabolic and enzymatic capabilities to allow them to tolerate and even benefit from the extreme depths, the lack of oxygen, the low pH of the surrounding waters, high temperatures due to volcanic releases, and the unique nutrient source of the vents. Choose the characteristics and their impact on enzyme activity that are not correct from the following statements.

Archaea are able to tolerate highly acidic pH environments and have proteins that will not denature in the low-pH environments that the bacteria are found in.

Whether a molecule is oxidized or reduced in a redox reaction depends on its reduction potential relative to the available electron donors and acceptors present that the organism can utilize. Given the following reduction potentials for various redox half reactions, in a lithotroph capable of utilizing ammonia as an energy source, which substances would be potential terminal electron acceptors for respiration? NO2 -/NH3 +0.34 VNO3 -/NO2 - +0.43 VO2/H2O +0.82 V

Both O2 and NO3 - are possible electron acceptors

Alternative autotrophic routes to the Calvin cycle such as the reverse citric acid cycle and the hydroxypropionate pathway are unified in their requirement for

CO2.

Distinguish how fermentation and respiration differ.

Fermentation forms organic acids and takes place in the absence of oxygen, while respiration forms water and carbon dioxide in the presence of oxygen.

When Beijerinck enriched for nitrogen fixers, he inoculated soil into two types of liquid media: one containing mineral salts and mannitol but no nitrogen source (flask A), and one containing mineral salts, mannitol, and an ammonium salt (flask B). After incubation in the presence of air, what types of organisms did he expect to find in each flask?

Flask A would contain nitrogen fixers that could grow both with or without ammonium; flask B would not contain nitrogen fixers but would contain organisms that could use ammonium.

As discussed in the introductory text, archaeans do NOT appear to use the Embden-Meyerhof-Parnas (glycolytic) pathway. Instead, they use alternate pathways to metabolize sugars. What is the function of this pathway in organisms that do use it? Choose the best answer.

Glucose is split into two molecules of pyruvate with a net gain of 2 ATPATP and 2 NADHNADH (regenerated to NAD+NAD+ to maintain redox balance in the third stage of glycolysis)

Which of the following statements is FALSE?

Most available nitrogen is in organic forms.

Which statement below demonstrates why the majority of organisms are heterotrophs?

The majority of organisms obtain their carbon from organic sources.

Archaeans also differ in their use of the pentose phosphate pathway. It may be absent or different from the pathway found in other domains. What is the function of the pentose phosphate pathway in organisms that use it?

The pentose phosphate pathway is important for breaking down glucose and The pentose phosphate pathway is important for the biosynthesis of pentoses and other sugars

To calculate the free energy (ΔG0′) of a reaction, you can subtract the free energies of formation (Gf0) of the reactants from those of the products. Given the following data, what will be true of this reaction? C6H12O6 + O2 → CO2 + H2O Gf0 : -917.3 0 -394.4 -237.2

The reaction will be exergonic.

Metabolic reactions can be assimilative or dissimilative. Which term, "assimilative" or "dissimilative," describes the reduction of sulfate by the sulfate-reducing bacteria (SRB) that have a symbiotic association with ANME?

The reduction of sulfate by SRB using electrons from ANME is dissimilative.

How is anaerobic respiration different from aerobic respiration?

The terminal electron acceptor in anaerobic respiration is not oxygen.

Chlorophyll and bacteriochlorophyll pigment molecules absorb light energy for photosynthesis. Each specific version of these molecules absorbs a different range of wavelengths of light, allowing different species of phototrophs to coexist by partitioning their use of the light spectrum. What controls the absorption spectrum of each particular chlorophyll/bacteriochlorophyll?

The various substituents on the tetrapyrrole ring alter the absorption properties of the pigments.

How does the proton motive force lead to production of ATP?

Translocation of three to four protons drives the F0 component of ATPase which in turn phosphorylates one ADP into ATP.

True or False: In electron transport systems, the electron carriers are membrane associated.

True

True or false: Photolytic systems REQUIRE a membrane to function.

True

The researchers used Cybb whose white blood cells lacked the enzymes to make an oxidative burst. When they infected these mice with ttrA- mutants (Salmonella that cannot reduce tetrathionate). Given this mix, would you expect to detect tetrathionate in the guts of these infected mice? (why or why not)

You wouldn't expect tetrathionate because thiosulfate wouldn't be oxidized by Cybb- white blood cells.

The path of electron flow in oxygenic phototrophs is referred to as the ________ scheme.

Z

Ferrous iron oxidation

can be aerobic or anaerobic; only small amounts of energy can be produced in acidic environments even though many of the organisms using this are acidophilic.

A chemoorganotroph and a photoautotroph in the same environment would NOT compete for

carbon and oxygen.

Carboxysomes are structures where ____.

carbon dioxide is fixed by Rubisco

The rising of bread dough is the result of

carbon dioxide produced by fermentation.

Whether an organism is classified as a photoheterotroph or a photoautotroph depends on its

carbon source

Organisms use different sources of carbon and energy. Archaeans do NOT use glycolysis and do NOT always use the pentose phosphate pathway, but use variations on these pathways for similar purposes. What is the best classification of this type of catabolism?

chemoorganotrophs

Most of the carbon in amino acid biosynthesis comes from

citric acid cycle intermediates and glycolysis products.

Which is one major difference between anaerobic and aerobic respiration?

electron acceptor

If ΔG0 is negative, the reaction is

exergonic and energy will be released.

Bacteriorhodopsin is a molecule that is used by bacteria to ___.

generate a proton motive force

Pure fermenters have an ATP synthase that they use to ___.

generate a proton motive force

Which metabolic cycle or pathway is LEAST likely to be invoked during the biosynthesis of DNA?

gluconeogenesis

Which of the following would NOT be required to grow an autotroph?

glucose

Nitrification

involves the aerobic oxidation of ammonia or nitrite.

Aerobic ammonia oxidation

is performed by Archaea and Bacteria and produces nitrite; Bacteria may oxidize the nitrite to nitrate.

Anaerobic oxidation of methane (AOM)

is performed by Archaea, often in sewage and in freshwater sediments; CO2 is often reduced using H2.

Acetogenesis

is performed by obligate anaerobes that use H2 as the major electron donor; both ion pumps and substrate level phosphorylation are used to conserve energy.

Nitrogenase is an enzyme that ___.

is unique to prokaryotes

Ecological theory states that for every organism there is at LEAST one ________, and the microenvironment where the organism is most successful is called the ________.

niche / prime niche

Fermentation occurs when there is no usable external electron acceptor (like O2) available for respiration. Fermentation products are made following glycolysis as a result of reactions that __________.

oxidize NADH so that NAD+ can be reused again in glycolysis

Autotrophs

perform CO2 fixation and utilize CO2 as their sole carbon source.

Which of the following represents increasing microbial diversity?

population-guild-community

According to ecological theory, each organism has one place where it will be most successful, called the __________.

realized niche

The role of an enzyme includes all EXCEPT which of the following?

reducing the rate of a reaction to allow for better control

Activation energy is the energy

required for a chemical reaction to begin.

The research team infected different sets of mice with 3 different strains of Salmonella. Wild-type (with a ttrA gene that enables the bacteria to use tetrathionate), ttrA- (loss of function mutant that cannot use tetrathionate), and ttrA restored (lacking ttrA on its chromosome, but present on the plasmid). They harvested the cecal contents to make the figure below:

serial dilutions and colony counts

If an oxidation reaction occurs

simultaneous reduction of a different compound will also occur, because electrons do not generally exist alone in solution.

Electron carriers used in electron transport chains are always found in membranes. Which one of the following statements is NOT a reason why electron transport chains are found in membranes?

so that they can transport NADH out of the cell to the periplasm

Which metric describes the proportion of EACH species present in a community?

species abundance

Given the paper and the data below, what can you infer about the value of tetrathionate to these Salmonella? The research team infected different sets of mice with 3 different strains of Salmonella. Wild-type (with a ttrA gene that enables the bacteria to use tetrathionate), ttrA- (loss of function mutant that cannot use tetrathionate), and ttrA restored (lacking ttrA on its chromosome, but present on the plasmid). They harvested the cecal contents to make the figure below

tetrathionate respiration is more efficent than fermentation

The proton motive force (PMF) is driven by __________.

the difference in charge across the plasma membrane with protons outside the membrane

____ does not provide carbon intermediates for the biosynthesis of amino acids or sugars.

the electron transport chain

The reduction potential (E0′) of a substance reflects its tendency to donate or accept electrons. The larger the difference (ΔE0′) between the reduction potentials of the electron donor and the electron acceptor, __________.

the greater the change in free energy (ΔG0′), and the greater the energy released

Which of the following is NOT a role of carotenoids?

to produce singlet oxygen

True or False: In natural samples it is often difficult to differentiate live cells from dead cells or cells from nonliving matter without special dyes

true

True or False: Many defined growth media that support microbial growth lack malonate, which is an important precursor for biosynthesis of lipid membranes. Based on this, we can infer cells also must have a metabolic pathway to generate malonate from other compounds.

true

True or False: Regeneration of oxaloacetate is essential for the citric acid cycle to be cyclical.

true

True or False: The net result of electron transport is the generation of a pH gradient and an electrochemical potential across the membrane.

true

Which intermediate compound(s) in the citric acid cycle is/are often used for biosynthetic pathways as well as carbon catabolism?

α-ketoglutarate, oxaloacetate, and succinyl-CoA