Microbiology Exam 3 Answers

Which of the following is a similarity between cyanobacteria and purple sulfur bacteria? A. Both do oxygenic phototrophy that generates O2 B. Both contain bacteriochlorophylls C. Both do both photosystems D. Both contain thykaloid membranes in the cytoplasm E. Both do carbon fixation via the Calvin cycle

E. Both do carbon fixation via the Calvin Cycvle

How is anaerobic respiration similar and different from aerobic respiration? Describe two similarities. Describe two differences.

Similarities: Both can use the same central metabolic pathways (glycolysis, pentose phosphate cycle and citric acid) and an electron transport chain. Both fully oxidize carbon in sugars to CO2. Both generate a large amount of ATP (36-38 ATPs per glucose) Differences: Anaerobic respiration uses an alternative final electron acceptor such as nitrate, nitrite, or sulfate instead of O2, the electron carriers will be different, and it generates slightly less maximum ATP.

List four features or properties of phototrophy that vary or differ in different types of phototrophic bacteria.

Types or kinds of pigments used and the wavelengths of light absorbed by them Organization of pigments in light harvesting complex Structure of Photosynthetic membrane structures - Electron donors (H2O, H2S, H2) and whether O2 produce Photosystem used: number and whether cyclic or non-cyclic photosystems Whether auto or heterotroph, How fix CO2

List three differences between phototrophy done by cyanobacteria and phototrophy done by green sulfur bacteria.

Use different electron donors (H2O) for cyanobacterium vs H2S, S or H2 for green sulfur Cyanobacterium produce oxygen while green sulfur do not. Photosynthetic pigments (cyanobacterium have phycobilins) Cyanobacterium do both photosystem I and II while green sulfur bacterium do PS I Carbon fixation: Cyanobacterium do Calvin cycle and Green sulfur do reductive TCA Light harvesting apparatus different:

Which of the following is a common feature of the production of cheese, pickled vegetables such as sauerkraut, and chocolate? A. Bacteria doing lactic acid fermentation of sugars play a key role in their production. B. Yeast doing alcoholic fermentation of sugars play a key role in their production. C. Bacteria doing lithotrophy play a key role in their production. D. Bacteria doing the Entner-Doudoroff pathway of sugars play a key role in their production E. All the other choices are correct.

A) Bacteria doing lactic acid fermentation of sugars play a key role in their production

Which of the following is the type of pigment that can absorb light in the near infrared range (800- 900 nm) that penetrates to deeper depths of water than red/blue light? A. Bacteriochlorophyll of Purple sulfur bacteria B. Chlorophyll of Cyanobacteria C. Carotenoids D. Phycobilins or phycobiliproteins E. Quinol

A) Bacteriochlorophyll of Purple Sulfur bacteria

Which of the following is NOT a similarity between aerobic respiration and oxygenic phototrophy? A. Both get electrons from H2O B. Both can produce ATP C. Both can produce reduced electron carriers (NADH or NADPH) D. Both use an electron transport system E. Both can pump protons across the membrane to create a proton motive force

A) Both get electrons from H20

Which of the following is a pathway that can convert glucose or sugar acids to 2 pyruvates with 6-P-gluconate as an intermediate in the process and yields 1 ATP, 1 NADH and 1 NADPH? A. Entner-Doudoroff pathway B. Glycolysis or Embden-Meyerhof-Parnas (EMP) pathway C. Pentose phosphate pathway D. Calvin cycle E. Tricarboxylic acid (TCA) cycle

A) Entner-Doudoroff Pathway

Which of the following is NOT a way cells capture or store energy in an usable form? A. Generation of ADP from ATP due to the phosphorylation of a protein. B. Generation of reduced NADH from NAD+ by oxidizing chemicals C. Generation of reduced NADPH from NADP+ D. Creation of a transmembrane ion gradient by pumping protons across a membrane E. Generation of ATP from ADP by using the flow of protons with the concentration gradient into the cell

A) Generation of ADP from ATP due to the phosphorylation of a protein

The oxidation of hydrogen sulfide (H2S) to sulfuric acid (H2SO4) could occur in bacteria doing _____. A. Lithotrophy B. Aerobic respiration C. Mixed acid fermentation D. Anaerobic respiration E. Oxygenic photosynthesis

A) Lithotrophy

Which of the following is NOT true about reactions in the central metabolic pathways? A. Most of the reactions can only be run in one direction and are not reversible B. Many reactions are oxidation and reduction reactions. C. Most reactions are catalyzed by a specific enzyme. D. Some reactions couple an energetically unfavorable half reaction with an energetically favorable half reaction. E. Some reactions are used in more than one metabolic pathway.

A) Most of the reactions can only be run in one direction and are not reversible

Phosphoenol phosphate (PEP) can be converted back and forth with ______ which is a metabolite in the TCA cycle and these reactions provide an alternative way to link glycolysis with the TCA cycle. During gluconeogenesis, this metabolite is converted into PEP. A. Oxaloacetate B. Succinate C. Fumarate D. alpha-ketoglutarate

A) Oxaloacetate

Describe the minimum components found in an electron transport chain used for respiration in bacteria.

An electron transport chain will consist of an initial electron donor complex that accepts electrons and protons from NADH or other molecules, and an electron acceptor complex that gives off the electrons to the final electron acceptor used by the cell (O2, NO3). In between the electron donor and acceptor complexes are one or more electron carriers, one of which will be a quinone.

Which of the following is the pathway that is noted to generate 4-, 5-, and 7-carbon intermediates that can be used for biosynthesis and yields NADPH? A. Glycolysis or the Embden-Meyerhof-Parnas (EMP) pathway B. Entner-Doudoroff pathway C. Pentose phosphate pathway D. Mixed acid fermentation E. Tricarboxylic acid (TCA) cycle or citric acid cycle

C) Pentose phosphate pathway

A series of sugar arrangements in which two- or three-carbon units of sugars are transferred to other sugar metabolites to generate a series of different metabolites is a feature observed in which of the following pathways? A. Glycolysis B. Tricarboxylic acid cycle(TCA) C. Pentose phosphate/hexose monophosphate pathway D. Mixed Acid fermentation E. Gluconeogenesis

C) Pentose phosphate/hexose monophosphate pathway

If an anaerobic respiratory pathway is described as dissimilarity, that means ____. A. The pathway is unique to that bacterium B. The pathway is not similar to aerobic respiration C. The product of the pathway is not incorporated into organic molecules D. The electron chain does not create a proton gradient E. The electron chain does not oxidize oxygen

C) The product of the pathway is not incorporated into organic molecules

The spectrum of light absorbed by phototrophic bacteria is principally determined by ________. A. Which photosystem they use B. Whether they are in the presence or absence of oxygen C. The types of pigments in their light harvesting antenna complexes D. Which electron carriers are in their photosystem E. The electron donor used

C) The types of pigments in their light harvesting antenna complexes

List three factors that would affect the energetics of a reaction.

Concentration of substrates vs products Change in Gibbs free energy from substrate to products Temperature Reduction potential value Entrophy of reaction (disorder)

Which of the following is true about electron carriers of electron transport chains? A. All the carriers carry two electrons B. All the carriers carry two protons C. All the carriers are bound to proteins D. All are in the membrane or associated with proteins in the membrane E. A and B

D) All are in the membrane or associated with proteins in the membrane

Which of the following is NOT true about glycolysis? A. Generates Fructose-6 phosphate as in intermediate B. Generates 2 pyruvates from each glucose C. Generates several precursor metabolites D. All bacteria do glycolysis E. Generates 2 net ATP and 2 NADH

D) All bacteria do glycolysis

Which of the following is a property of all phototrophic bacteria? A. All use bacteriochlorophyll B. All use the same photosystem C. All types produce oxygen D. All light harvesting pigments are located or associated with membranes E. All types fix carbon by using the Calvin System

D) All light harvesting pigments are located or associated with membranes

Which of the following is a difference between anaerobic respiration and aerobic respiration? A. Anaerobic respiration does not use glycolysis B. Anaerobic respiration does not utilize the TCA cycle C. Anaerobic respiration does not fully oxidize carbon atoms in sugars to CO2 D. Anaerobic respiration uses an alternative final electron acceptor besides O2 E. Anaerobic respiration does not use an electron transport chain to pump protons across the cell membrane in order to generate proton motive force

D) Anaerobic respiration uses an alternative final electron acceptor besides O2

Which of the following is a similarity between lithotropy and anoxygenic phototrophy? A. Both produce O2 B. Both reduce nitrate to N2 C. Both use electron transport chains D. Both can get electrons from H2S or H2. E. A and B

D) Both can get electrons from H2S or H2

A similarity between the Calvin cycle and the pentose phosphate cycle is ______? A. Both generate NADPH B. Both generate ATP C. Both generate NADH D. Both go through a series of sugar rearrangements to form sugars of different lengths E. Both generate CO2

D) Both go through a series of sugar rearrangements to form sugars of different lengths

A similar porphyrin ring structure is found in which of the following? A. Flavoproteins and Carotenoids B. Phycobilin proteins and iron-sulfur proteins C. Quinones and iron-sulfur proteins D. Cytochromes and chlorophylls E. Bacteriorhodopsins and Iron-sulfur proteins

D) Cytochromes and chlorophylls

Which of the following is NOT a reason why a type of bacteria may do fermentation instead of aerobic respiration? A. No oxygen is present in its environment B. The excreted end products of its fermentation inhibit the growth of some other microbes in its environment C. The bacterium can do fermentation more rapidly and thus consume the food source quicker than bacteria doing aerobic respiration D. Doing fermentation allows the bacteria to assimilate nitrogen

D) Doing fermentation allows the bacteria to assimilate nitrogen

The term used to describe an organism that obtains its electrons from inorganic molecules is ______ A. Heterotroph B. Organotroph C. Phototroph D. Lithotroph E. Autotroph

D) Lithotroph

Which of the following is the form of nitrogen that can be directly incorporated or assimilated into organic materials by bacteria by linking to alpha-ketoglutarate or glutamate? A. N2 B. NO2- C. NO3- D. NH4+ E. NOH2+

D) NH4+

Which of the following is a reason why an organism may run some or all of the reactions of the TCA cycle backwards relative to their normal direction? A. In order to make precursor metabolites B. In order to incorporate or fix CO2 C. In order to regenerate NADH D. In order to generate NADPH E. A and B

E) A and B

Which of the following is true about transmembrane gradients in bacterial cells? A. Can be created by a difference between the pH outside verse inside the cell B. Can be created by a difference between the total charge outside verse inside the cell C. Can be created by a difference between the concentration in protons (H+) ions outside verse inside the cell D. Can be created by a difference in the concentration in sodium (Na+) ions outside verse inside the cell E. All the other choices are correct

E) All the other choices are correct

The reduction of nitrate (NO3-) and nitrite (NO2-) to N2 occurs in organisms doing _____ ? A. Aerobic respiration B. Anoxygenic phototrophy C. Mixed acid fermentation D. Lithotrophy E. Anaerobic respiration

E) Anaerobic respiration

Chlorophyll is observed in which of the following? A. Green and purple bacteria B. Only eukaryotic phototrophs C. Cyanobacteria and green bacteria but not purple bacteria D. All phototrophic bacteria E. Cyanobacteria and eukaryotic phototrophs

E) Cyanobacteria and eukaryotic phototrophs

Which of the following is NOT true about the Entner-Doudoroff (ED) pathway? A. Alternative way to break down glucose to pyruvate done by some bacteria B. Generates 6-P-gluconate as an intermediate C. Generates NADPH in addition to NADH D. Enables the utilization of sugar acids E. Generates more ATP per glucose than glycolysis

E) Generates more ATP per glucose than glycolysis

You have grown a bacterium in media with glucose as the sole carbon source and then after incubation in the culture media you detect lactic acid, ethanol, and CO2. What type of metabolism was the bacteria doing? A. Anaerobic respiration B. Mixed acid fermentation C. Propionic acid fermentation D. Homofermentative lactic acid fermentation E. Heterofermentative lactic acid fermentation

E) Heterofermentative lactic acid fermentation

Which of the following is the difference between homolactic fermentation and heterolactic fermentation? A. Heterolactic fermentation can start from many different sugars while homolactic can only start from lactose 'B. Homolactic fermentation generates homoserine while heterolactic fermentation generates heteroserine C. Homolactic fermentation generates lactate while heterolactic fermentation generates butanediol in addition to lactate D. Homolactic fermentation generates homolactate while heterolactic fermenation generates heterolactate E. Homolactic fermentation generates only lactate while heterolactic fermenation generates ethanol and CO2 in addition to lactate

E) Homolactic fermentation generates only lactate while heterolactic fermenation generates ethanol and CO2 in addition to lactate

Which is NOT true about carbon fixation? A. Is the incorporation of CO2 into organic molecules B. Across all types of bacteria, four different ways of fixing CO2 are observed. C. One mechanism involves using two CO2 molecules to create acetyl-CoA D. One mechanism involves adding CO2 to a 5-carbon sugar E. One mechanism involves running glycolysis backwards

E) One mechanisms involves running glycolysis backwards

What electron carrier is found in the middle of most electron transport systems and is a lipid that diffuses in the membrane and is not permanently held by proteins and carries electrons between electron transport protein complexes? A. Riboflavin B. Iron-sulfur clusters C. Cytochromes D. Chlorophyll b E. Quinones

E) Quinones

Which of the following is a common feature of all fermentations? A. All generate lactic acid as an end product. B. All generate NADH and then consume NADH by reducing an organic intermediate C. All start from glucose. D. All generate an acid as an end product. E. Do not generate any ATP.

B) All generate NADH and then consume NADH by reducing an organic intermediate

Which of the following is NOT a difference between anoxygenic photosynthesis from oxygenic photosynthesis? A. Anoxygenic photosynthesis has only one transport chains instead of two B. Anoxygenic photosynthesis can only generate ATP while oxygenic generates ATP and NADPH C. Anoxygenic photosynthesis does not generate O2 D. Anoxygenic photosynthesis gets its electron from a different molecule such as H2S instead of H2O E. Anoxygenic photosynthesis uses bacteriochlorophylls instead of chlorophyll a

B) Anoxygenic photosynthesis can only generate ATP while oxygenic generates ATP and NADPH

Which of the following is NOT true about alcoholic fermentation? A. Source of starting material can be sugars released from malting grains B. Generates 32 ATPs per glucose molecules C. Done by yeast and a few kinds of bacteria D. Also generates some CO2

B) Generates 32 ATPs per glucose molecules

Which of the following is the pathway that converts glucose to 2 pyruvates via a fructose-1,6-bisphosphate intermediate and yields 2 NADHs and a net of 2 ATPs? A. Entner-Doudoroff pathway B. Glycolysis or Embden-Meyerhof-Parnas (EMP) pathway C. Pentose phosphate pathway D. Calvin cycle E. Tricarboxylic acid (TCA) cycle

B) Glycolysis or Embden-Meyerhof-Parnas (EMP) pathway

Which of the following contains a single type of photosystem and that photosystem gives up the excited electrons to NAD(P)+ to generate reduced NADPH? A. Cyanobacteria B. Green sulfur bacteria C. Purple non-sulfur bacteria D. Purple sulfur bacteria

B) Green sulfur bacteria

Which of the following is NOT true about the Tricarboxylic acid (TCA) cycle? A. The TCA cycle can be run backwards (oxaloacetate to citrate). B. If an organism is doing TCA pathway, they will do all the steps or reactions in the pathway. C. Some of the metabolites produced in the pathway are precursor metabolites D. The TCA cycle can be used to fix carbon E. Some bacteria can skip some of the steps to avoid the release of carbon as CO2

B) If an organism is doing TCA pathway, they will do all the steps or reactions in the pathway.

The difference in charge and the difference in pH are two important factors in determining ______, A. ∆G or change in Gibbs Free energy B. Proton motive force C. Photon potential D. Chemolithotrophic potential E. Reduction potential

B) Proton motive force

If the reaction A + B > C + D occurs in cells, which of the following must be true? A. The deltaG for each half reaction (A to C) and (B to D) must be negative B. The overall deltaG for the reaction under the current conditions would be negative C. The overall reduction potential would be negative D. The reaction can never go backwards i.e. C + D > A + B E. A and C

B) The overall deltaG for the reaction under the current conditions would be negative

There are bacteria that can synthesize methane from CO2. This energetic unfavorable reaction is catalyzed by coupled the reduction of CO2 to _____ A. Photons of light B. The oxidation or splitting of H2 C. The reduction of nitrate to ammonia D. Proton motive force E. The oxidation of sugars to CO2

B) the oxidation or splitting of H2

Chemoautotrophs obtain their carbon from _______ and their energy from ______ A. CO2, light B. CO2, inorganic chemicals C. organic compounds, organic compounds D. organic compounds, light E. organic compounds, inorganic compounds

B. CO2, inorganic chemicals

What are three similarities between aerobic respiration and oxygenic phototrophy?

Both use electron transport chains to capture energy Both create proton gradients Both synthesis ATP Both use similar electron carriers (cytochrome and chlorophyll are similar, quinones) Both generate reduced electron carriers (NADH or NADPH) Portions of both occur in a membrane (the electron transport chains)

List three kinds of food or beverages in which microorganisms play a role in their production. Then for each describe the type of metabolism that occurs during the production of the food and what type of microorganisms (bacteria, fungi, protozoan, virus) are involved in the production of the food.

Bread - alcoholic fermentation of sugar by yeast Beer, wine and distilled spirits - alcoholic fermentation of sugars by yeast Yogurt, sour cream, buttermilk, cheese - lactic fermentation of milk by bacteria, also fungi in some cheeses Fermented vegetables - lactic acid fermentation by bacteria of sugars Fermented meats - lactic acid fermentation by bacteria Chocolate - lactic acid and acetic acid fermentation by bacteria and yeast

What is a common feature of glycolysis, tricarboxylic acid (TCA) cycle and the pentose phosphate pathway? A. None generate ATP directly B. All generate NAD+ C. All generate at least one precursor metabolite. D. All do 2 carbon sugar rearrangements E. All the other choices are correct

C) All generate at least one precursor metabolite

Bacteria can grow on fatty acids as their sole carbon source. The fatty acids would be broken apart into two-carbon units that enter the central metabolic pathways as acetyl-CoA. However, if the cells ran all the acetyl-CoA into the typical TCA cycle and did aerobic respiration, a problem would arise. What is that issue? A. NAD+ would not be regenerated and it needs NAD+ in order to do glycolysis to generate ATP. B. All the acetyl-CoA would be converted to alcohol. C. All the entering carbon would be lost as CO2, and thus no carbon atoms can be siphoned off to create precursor metabolites. D. No NADHs would be generated and so no ATP would be generated E. No proton gradient would be generated.

C) All the entering carbon would be lost as CO2, and thus no carbon atoms can be siphoned off to create precursor metabolites

Which of the following is the difference between cyclic photosystems and noncyclic photosystems? A. Cyclic photosystems generate O2 while noncyclic photosystems do not B. Cyclic photosystems do pump protons across the membrane while non-cyclic photosystems do not C. Cyclic photosystems do not give up electrons to NAD(P)+ while noncyclic photosystems do give up electrons to NADP+ to generate NADPH D. Cyclic photosystems have bacteriochlorophyll in the reaction center, while noncyclic photosystems have carotenoids E. A and B

C) Cyclic photosystems do not give up electrons to NAD(P)+ while noncyclic photosystems do give up electrons to NADP+ to generate NADPH

Which of the following is NOT a way cells capture energy in an usable form? A. Generation of ATP from ADP by substrate level phosphorylation B. Generation of reduced NADH from NAD+ by oxidizing chemicals C. Generation of oxidized NADP+ from NADPH by reducing chemicals D. Creation of a transmembrane ion gradient by pumping protons across a membrane E. Generation of ATP from ADP by using the flow of protons with the concentration gradient into the cell

C) Generation of oxidized NADP+ from NADPH by reducing chemicals

Which of the following lists the pathways that need to be run in some manner by all types of bacteria in order to generate precursor metabolites? A. Glycolysis and the Tricarboxylic acid cycle B. Glycolysis and Calvin cycle C. Glycolysis, Pentose phosphate and Tricarboxylic acid cycle D. Calvin cycle, Entner-Doudoroff, and Tricarboxylic acid cycle E. Entner-Doudoroff, Pentose phosphate and Calvin cycle

C) Glycolysis, Pentose phosphate, and Tricarboxylic acid cycle

In one observes a bacterium getting energy and electrons by oxidation of inorganic chemicals such as H2S or H2, the bacterium would be described as capable of doing _______ A. Aerobic respiration B. Anaerobic respiration C. Lithotrophy D. Oxygenic Photoautotrophy E. A form of fermentation

C) Lithotrophy

After CO2 is fixed as part of the Calvin cycle, the products generated can enter reactions similar to _______? A. Glycolysis B. the TCA cycle C. the Pentose phosphate pathway D. Heterolactic acid fermentation E. Entner-Doudoroff (ED) pathway

C) the Pentose phosphate pathway

Explain the role of electron transport system in metabolism in bacterial cells

Electron transport systems in respiration and oxidative phosphorylation accept electrons from an electron donor chemical such as NADH. The electrons are transfer to different electron carries in the electron transport system and each transfer lowers the potential energy and then ultimately given to an electron acceptor such as O2 or NO3 which are then reduced. Often during the process, hydrogen protons are pumped outside the cell to help create a proton gradient. The proton gradient can be used to synthesize ATP. An electron transport system is also used in photosynthesis where the electron excited by photons is passed to an electron transport system which can give the electron to generate NADPH and protons are also transported so that ATP can be synthesized.

Some bacteria can grow using citrate as its sole carbon and energy source. Citrate is a metabolite in the Tricarboxylate acid cycle (TCA) and the citrate would enter the central metabolic pathways there. Explain how the bacterium would run the central metabolic pathways to obtain energy and to produce all the precursor metabolites it needs?

It could run the TCA cycle forward to capture energy in the form of NADH or FADH or part forward and part in reverse. The NADH and FADH could be used to generate a proton gradient and ATP via using respiration. The TCA cycle would generate oxaloacetate which it could be converted to PEP so that it could then run glycolysis and pentose phosphate backwards to generate precursor metabolites.

In a chemoheterotroph doing aerobic respiration of glucose, glycolysis is usually linked to the TCA cycle by a reaction that converts pyruvate to acetyl-CoA which enters the TCA cycle. Under other conditions, glycolysis and TCA cycle can be linked by other reactions that convert a metabolite of one of the pathways into a metabolite in the other pathway. Describe 3 other reactions that can convert a metabolite in one of the two pathways into a metabolite in the other pathway in a single step. If the reaction is reversible, it can count for 2 ways by indicating that.

Pyruvate + CO2 + ATP → oxaloacetate + ADP Oxaloacetate + ATP ↔ PEP + ADP both directions Malate + NAD+ ↔ Pyruvate + NADH + CO2, both directions

Look at Exam 3 Figure 1 shown on the separate page which shows a metabolic pathway as shown by Metacyc.

a. Found: 4-9 b. Not found: 1, 2, and 3 c. Unique: 5 and 6 d. When growing on foods that come in as 2-carbon units, the bacteria uses the glyoxylate shunt to bypass steps 4 and 5 to avoid the loss of both carbons as CO2 so some carbon can be used for biosynthesis and is not lost as CO2. e Bacteria can do incomplete TCA in which they do reactions 1-5 in the forward direction and reactions 9-6 in the backward direction. Bacteria may do this when they are not doing aerobic respiration. Another alternative is to run the pathway backwards to fix carbons.

The reaction CO2 + 3 H2 → CH4 + 2 H2O has been observed in nature. Look at Table 14.1 included and determined its energetics and answer the following question. a. Is the reaction as written energetically favorable based on the ΔG value? b. Describe one way the rate of the reaction towards CH4 could be stimulated.

a. No, deltaG is positive b. The reaction could be coupled to a half reaction that is energetically favorable. The reaction would be stimulated if the concentration of the substrates was much higher than the products. Increasing the temperature will also increase the reactions.

Compare aerobic respiration and fermentation. a. List two similarities between aerobic respiration of glucose and lactic acid fermentation of glucose? b. List or describe 3 differences between aerobic respiration of glucose and lactic acid fermentation of glucose?

a. Similarities: 1. Both use glycolysis or ED, 2. Both generate ATP 3. Both generate NADH or NADPH but fermentation later consumes it. b. Differences: Aerobic respiration generates more ATPs, more NADH, uses electron transport chain, requires oxygen. Aerobic respiration fully oxidizes all carbon in glucose to CO2 while fermentation only partial oxidizes the carbon to lactic acid