Micro 302 Iowa State University Exam 4 Previous HW Questions and Quizzes

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.

Which of the following pathways is found in ALL living organisms?

Pentose phosphate shunt

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.

Based on the phylogenetic tree below, which of the following statements is FALSE?

Species D is more closely related to species C than to species E

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

A population consists of

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

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

anaerobic oxidation of methane (AOM)

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.

acetogenesis

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

aerobic ammonia oxidation

Most metabolic pathways are amphibolic, which means they ___.

are both anabolic and catabolic

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

autotrophs

The many and varied electron and carbon sources that different microbes use makes them excellent tools for ___.

bioremediation

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.

Fermentation is very inefficient, so organisms that are fermenting will ___.

consume more than non-fermentors

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.

T/F: 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

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.

ferrous ion oxidation

The metabolic diversity of photosynthetic bacteria stems from different

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

Enzymes catalyze chemical reactions by ___.

lowering the activation energy, thus increasing the rate of the reaction.

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

mixotrophs

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

syntrophs

Aerobic respiration and anaerobic respiration will always use different ____.

terminal electron acceptors

Fatty acids are biosynthesized using ________ carbon molecules along with the help of ________.

two/acyl carrier proteins

Gluconeogenesis is the process of synthesizing __________.

glucose from other compounds

The Embden-Meyerhof-Parnas pathway is another name for

glycolysis

The ____ is required for organisms to survive solely on acetate or other 2-carbon food sources, but not for organisms to use pyruvate or glucose as their food source.

glyoxylate cycle

Culture-independent approaches avoid issues associated with

growing organisms in the lab

use organic carbon as their carbon source.

heterotrophs

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. -The pentose phosphate pathway is important for the biosynthesis of pentoses and other sugars.

Which metabolic strategies invoke the proton motive force for energy conservation?

-chemoorganotrophy -photoautrophy -aerobic catabolism

Which of the following factors alters the speed at which an enzyme catalyzes a chemical reaction?

-temperature of the reaction -concentration of the product -concentration of substrate -pH of the reaction solution

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.

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 V NO3 -/NO2 - +0.43 V O2/H2O +0.82 V

Both O2 and NO3 - are possible electron acceptors

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

Z

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 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?

Glucose is split into two molecules of pyruvate with a net gain of 2 ATP and 2 NADH (regenerated to 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.

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.

Life on Earth is dependent upon the activity of photonic energy-capturing pigments (large molecules that absorb photonic energy from light at specific wavelengths) in plants, algae, and some bacteria. These colored pigments are able to capture the energy of a photon and split water to release an excited electron that will be used to drive further metabolic activities. Photosynthetic plants and prokaryotes are found in many different environments throughout the world. These pigments or pigmentlike molecules may be a target for searches on other planets when searching for traces of the building blocks for photosynthetic organisms. Photosynthetic pigments are used by autotrophs in the process of photosynthesis to capture solar energy that will be used to __________.

break water into free hydrogen and oxygen while liberating electrons from the hydrogen atoms

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

carbon and oxygen

Carboxysomes are structures where ____.

carbon dioxide is fixes 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

use inorganic electron donors and CO2 as a carbon source.

chemolithotrophs

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

use inorganic or organic chemicals as energy sources.

chemotrophs

Most of the carbon in amino acid biosynthesis comes from

citric acid cycle intermediates and glycolysis products.

Looking at the Electron Tower, those compounds with lower Eo values will ____ than those with higher Eo values.

donate electrons to

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.

T/F: The diversity of microorganisms in culture collections is representative of the diversity of microorganisms found in nature.

false

T/F: The proton motive force is most often generated by splitting of H2.

false

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

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

involves the aerobic oxidation of ammonia or nitrite.

nitrification

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

Which of the following is NOT a part of all electron transport chains ___.

oxygen

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

phototrophs

Which of the following represents increasing microbial diversity?

population-guild-community

Cyclic photophosphorylation is common to ___ bacteria.

purple non-sulfur bacteria

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

If the ΔG0′ of a reaction is positive, that means that energy is ________ and the reaction is ________.

required / endergonic

Activation energy is the energy

required for a chemical reaction to begin.

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

The ATP generated in the Embden Meyerof Parnas pathway is made through ___.

substrate-level phosphorylation

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

Photolytic systems REQUIRE a membrane to function.

true

T/F: Organisms grown with CO2 as its sole carbon source must have energy in the form of ATP as well as reducing power.

true

T/F: In electron transport systems, the electron carriers are membrane associated.

true

T/F: In natural samples it is often difficult to differentiate live cells from dead cells or cells from nonliving matter without special dyes.

true

T/F: 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

T/F: New areas of research have begun examining the different mechanisms here on Earth to have a metabolism in the absence of gaseous oxygen. Since most planets that have been identified so far lack atmospheric oxygen, the need to study anaerobic metabolisms here on Earth becomes apparent. The lack of oxygen in many environments (e.g., undersea sulfur vents, compost piles, or intestinal lumens) here on Earth has created a selective pressure for numerous organisms to evolve new metabolic pathways to maintain the metabolic reactions required for energy production. In aerobic organisms, oxygen is required in cellular respiration and photosynthesis to act as a final electron acceptor at the end of the electron transport chain. A high-energy electron is passed through a series of proteins that use the electron's energy to transport a hydrogen atom across a membrane to set up an electrochemical gradient. After the excited electron has been sent through the transport chain, the electron is paired with a hydrogen atom and bound to an available oxygen molecule to form water. The lack of oxygen as a final electron acceptor in oxidative phosphorylation has forced some organisms to utilize other molecules, such as ones containing sulfur, to be reduced in the final step. Other alternate mechanisms include the use of fermentation as a means of oxidizing NADH so that more cycles of glycolysis can continue. If these steps are happening here on Earth, should we not be looking for similar compounds on other planets? The reduction of nitrate to nitrite and water by Mycobacterium tuberculosis is the anaerobic version of the use of the reduction of oxygen as a final electron acceptor under aerobic conditions. This metabolic characteristic may be useful in distinguishing this bacterial species and other nitrate reducers from nonreducers when trying to identify a new species or possible environmental niche.

true

T/F: Regeneration of oxaloacetate is essential for the citric acid cycle to be cyclical.

true

T/F: The net result of electron transport is the generation of a pH gradient and an electrochemical potential across the membrane.

true

A positive reaction in a Phenol red broth test is ____.

yellow

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