Micro CH 5,6

Examine the figure above depicting the preparatory step and the Krebs cycle, and identify statements that correctly describe these processes. Select all statements that correctly describe the preparatory step and the Krebs cycle.

- The oxaloacetic acid that accepts the acetyl group is regenerated, enabling the cyclic nature of this process. - It takes two "turns" of the Krebs cycle to process the pyruvic acid molecules resulting from the glycolysis of one glucose molecule. - There are five oxidation-reduction reactions depicted. - The equivalent of one ATP is made for each turn of the Krebs cycle. - The potential energy in the pyruvate is transferred to coenzymes NAD+ and FAD. - Carbons from pyruvic acid end up as CO2. You have identified correct statements about the Krebs cycle. At this point, most of the potential energy that was originally in the glucose molecule is now in the electrons carried by NADH and FADH2. The next process will involve moving the electrons from these coenzymes down a series of electron carriers until they reach their lowest energy level in the final electron acceptor. The energy given up by the electrons will be use to phosphorylate ADP to make ATP.

In Bacteria, the proton motive force can be used to power

- flagella - active transport - synthesis of ATP

8. Differentiate complex and chemically defined media.

A chemically defined medium is one in which the exact chemical composition is known. A complex medium is one in which the exact chemical composition is not known.

A chemostat is continuous culture system that is designed to promote and prolong exponential growth and prevent bacteria from entering stationary phase. How might this work?

Chemostats provide a continued source of fresh nutrients and remove wastes and dead bacterial cells.

The data in the table indicate that S. aureus is a(n)

facultative halophile.

Heterotroph

organic carbon sources

Chemoorganotroph

organic energy sources

Cyanobacteria are a type of

photoautotroph.

Consider the glycolysis pathway. Select all statements that correctly describe glycolysis.

- Glucose is the original electron donor. - The 6-carbon skeleton of glucose is enzymatically split into two 3-carbon compounds. - More ATP is formed than is consumed in this process. - Glyceraldehyde 3-phosphate is oxidized, and NAD+ is reduced to NADH. You have identified correct statements about glycolysis. The pyruvic acid that is formed during the last step of glycolysis may be converted to acetyl CoA and enter into Krebs cycle to continue with cellular respiration, or it may enter into fermentation reactions. The specific outcome will depend on the presence of O2 and the specific enzymes in the cell.

After a period of rapid growth (log phase), bacterial growth rates will slow and enter the stationary phase. The number of viable cells no longer increases, but instead stays constant. In this activity you will indicate the statements that correctly describe what is happening during stationary phase. Select each statement that accurately describes what is happening to bacterial cultures during stationary phase.

- Harmful waste products may be accumulating. - The number of cells that are dying is balanced by the number of new cells that are being formed. - The cells are likely running out of nutrients. During the stationary phase, the number of viable cells does not increase and remains constant, or stationary. This phase begins as the nutrient supply is depleted and/or waste products begin to accumulate at a toxic level.

Compare and contrast three metabolic pathways by choosing whether the statement applies to fermentation.

- Process includes glycolysis - The coenzyme NAD+ plays an important role in the pathway. - End products may include lactic acid or ethanol. - A total of 2 ATP are produced per molecule of glucose input. - Can generate ATP in the absence of O2. You have correctly associated each of the statements with the metabolic processes. Some microorganisms rely on just one of these metabolic processes. For example, Pseudomonas spp. use aerobic respiration to release energy from glucose. Other microorganisms possess multiple metabolic pathways and maybe able to do aerobic respiration in the presence of O2, but when deprived of O2 will revert to anaerobic respiration and/or fermentation. Other microorganisms rely entirely on fermentation.

Compare and contrast three metabolic pathways by choosing whether the statement applies to aerobic respiration.

- Process involves electron transport and chemiosmosis - End products are CO2 and H2O - Process includes glycolysis - The coenzyme NAD+ plays an important role in the pathway. - Much or most of the ATP produced is produced by oxidative phosphorylation. - A total of 38 ATP are produced per molecule of glucose input. - Process involves the Krebs cycle You have correctly associated statements with the aerobic respiration.

Compare and contrast three metabolic pathways by choosing whether the statement applies to anaerobic respiration.

- The coenzyme NAD+ plays an important role in the pathway. - Much or most of the ATP produced is produced by oxidative phosphorylation. - Process involves electron transport and chemiosmosis - Process includes glycolysis - Process involves the Krebs cycle - Between 2 and 38 ATP are produced per molecule of glucose input. - Can generate ATP in the absence of O2. You have correctly associated statements with the anaerobic respiration.

Suppose you take sample of cells growing exponentially in rich media and use them to inoculate a flask of minimal (nutrient poor) media. How would the growth curve for minimal media compare to that of rich media? (select all that apply)

- The time in lag phase would increase. - The slope of log phase would decrease.

Scientist discover a new phototropic bacteria and categorize it as "purple non-sulfur". Based on its grouping, you can predict this microbe likely ___.

- is prokaryotic - uses photophosphorylation - uses bacteriochlorophylls

Arrange the events below into a sequence that traces the flow of energy through the electron transport chain and chemiosmosis.

-Electron carriers donate electrons to electron transport chain -Electrons release energy causing H+ ions to be transported against their concentration gradient. -H+ concentration gradient increases. -H+ ions diffuse along their concentration gradient inducing ATP synthase to generate ATP.

What factors that are important when formulating culture media?

-pH -Water availability -Oxygen (O2) levels A culture medium must be formulated to support the growth of the desired organisms, including an appropriate pH and oxygen level as well as the presence of water. Organisms also require sources of carbon, nitrogen, and various other nutrients and growth factors.

Based on our calculations of E. coli aerobic respiration on the last slide, what is the maximum ATP yield per 1 glucose if: You are a bacteria grown with a competitive inhibitor of glyceraldhyde 3-phosephate (G3P) dehydrogenase, the enzyme that catalyzes the first step of the pay-off phase of glycolysis.

0

Based on our calculations of E. coli aerobic respiration on the last slide, what is the maximum ATP yield per 1 glucose if: You are an aerobic bacteria with a mutation in citrate synthetase, and enzyme in the Krebs cycle, that now renders the enzyme (and cycle) non-functional.

14

This activity asks you to calculate the size of a bacterial population during exponential growth. A broth medium has been inoculated, and microbial numbers will be counted periodically to generate a bacterial growth curve. At 2 hours after inoculation, the culture has progressed through lag phase and is now in log phase. At this point, the population size is 1 million cells. The generation time is 30 minutes. Assuming the continuation of log growth, how many cells would there be at 2 hours of growth in log phase?

16 million There would be approximately 16 million cells. In the 2-hour interval of log growth, there are four 30-minute generations. This is four doublings of the 1 million organisms present at hour 2.1 million cells x 24 = 16 million cells

Glycolysis generates energy by producing?

2 ATP and 2 NADH Glycolysis is the first step of aerobic cellular respiration, and produces two molecules of pyruvate by splitting glucose in half. This process removes high-energy electrons from glucose and transfers them to the electron carrier NADH. NADH contains high-energy electrons, and without the high-energy electrons it is NAD+. Breaking glucose involves the net input of 2 ATP molecules, but the energy producing stage of glycolysis produces a 4 ATP. Thus, the net gain of ATP from glycolysis is 2 ATP.

The Kreb's cycle will yield _______________ (per 1 molecule of glucose)

2 ATP, 2 FADH2, 6 NADH, 4 CO2

One 1 molecule of glucose can yield ______during glycolysis.

2 ATP, 2 NADH, 2 pyruvate

The preparatory step will yield __________ (per 1 molecule of glucose)

2 NADH, 2 CO2, 2 acetyl-CoA

Which of the following statements are TRUE? 1-Electron carriers are located at ribosomes. 2-ATP is a common intermediate between catabolic and anabolic pathways. 3-ATP is used for the long-term storage of energy and so is often found in storage granules. 4-Anaerobic organisms are capable of generating ATP via respiration. 5-ATP can be generated by the flow of protons across protein channels.

2, 4, 5

Based on our calculations of E. coli aerobic respiration on the last slide, what is the maximum ATP yield per 1 glucose if: You are an aerobic bacteria that encounters a chemical toxin. This toxin alters your inner membrane so it is "leaky" to protons.

4

In aerobic cellular respiration, if four molecules of pyruvic acid enter steps two, the formation of acetyl CoA and three, the Krebs cycle, how many molecules of ATP, NADH, and FADH2 will be formed?

4 ATP, 16 NADH, 4 FADH2 The products of each step of the formation of acetyl CoA and the Krebs cycle must be accounted for. For each glucose that enters glycolysis, 2 pyruvic acid molecules enter the Krebs cycle. Each pyruvic acid molecule generates 1 ATP, 4 NADH, and 1 FADH2 molecules. So, 4 pyruvic acids would generate 4 ATP, 16 NADH, 4 FADH2.

Most bacteria grow best at pH

7

An organism is able to growth both aerobically and anaerobically (either through respiration or fermentation). Which growth curve represents fermentative growth.

A

In the table, in which medium (or media) would an autotroph grow but a heterotroph could not?

A

Which of the following is the best definition of oxidative phosphorylation?

A proton gradient allows hydrogen ions to flow back into the cells through transmembrane protein channels, releasing energy that is used to generate ATP.

What is the intermediate product formed by pyruvic acid during alcoholic fermentation?

Acetaldehyde

Which of the following is true of aerobic respiration compared to anaerobic respiration?

Aerobic respiration uses oxygen as a final electron acceptor, whereas anaerobic respiration uses an inorganic molecule other than oxygen as the final electron acceptor. Correct. In anaerobic respiration, the final electron (hydrogen) acceptor is an inorganic substance other than oxygen, such as nitrate, sulfate, or carbonate.

Which of the following is NOT true of biofilms?

Biofilms are rarely found in nature, but easily grown in the lab.

7. Fill in the following table with the carbon source and energy source of each type of organism. Organism a) Photoautotroph b) Photoheterotroph c) Chemoautotroph d) Chemoheterotroph

Carbon Source a-1) CO2 b-1) CO2 c-1) Light d-1) Inorganic molecules Energy Source a-2) Organic molecules b-2) Organic molecules c-2) Light d-2) Organic molecules

The area around and above the biofilm shown below is filled with an antibiotic. Of the four cells labeled in the biofilm, which would be exposed to the LOWEST concentration of antibiotics?

Cell 4 Antibiotic molecules move into a biofilm by diffusion. Cells near the surface of the biofilm or near a water channel are exposed to the highest concentrations of antibiotic. The matrix surrounding deeper layers of the biofilm acts as a barrier to antibiotic diffusion. The concentration of antibiotics therefore decreases as one goes deeper into the biofilm. Cells near the surface are easily killed off, but those in the deeper layers, like Cell 4, are less affected. This is one of the reasons biofilms are so hard to completely remove with antibiotic treatment.

10. What nutritional type is a colorless microbe that uses the Calvin-Benson cycle, uses H2 as the electron donor to its ETC, and uses elemental S as the final electron acceptor in the ETC?

Chemoautotroph

10. A prokaryotic cell hitched a ride to Earth on a space shuttle from some unknown planet. The organism is a psychrophile, an obligate halophile, and an obligate aerobe. Based on the characteristics of the microbe, describe the planet.

Cold, salty, aerobic

Which of the following statements regarding competitive inhibitors is true?

Competitive inhibitors decrease the rate of enzyme activity.

What enables competitive inhibitors to bind to a specific enzyme?

Competitive inhibitors have structures that resemble the enzyme's substrate.

Which of the following is a bacterium that performs oxygenic photosynthesis?

Cyanobacteria Yes! Like plants and algae, cyanobacteria are oxygenic; meaning that their photosynthetic process generates oxygen.

4. Seven methods of measuring microbial growth were explained in this chapter. Categorize each as either a direct or an indirect method.

Direct methods are those in which the microorganisms are seen and counted. Direct methods are direct microscopic count, plate count, filtration, and most probable number. Growth is inferred by indirect methods: turbidity, metabolic activity, and dry weight.

Why does FADH2 yield less ATP than NADH?

FADH2 electrons enter the electron transport chain at a lower energy level.

Most pathogenic bacteria are thermophiles.

False

What would you expect to observe when a halophile that cannot ferment mannitol is cultured on mannitol salts agar?

Good growth accompanied by no change in color of the medium. Mannitol salts agar (MSA) is a selective medium because its high salt concentration only allows halophilic organisms (such as Staphylococcus) to grow. It is a differential medium, because it changes color from red to yellow in the vicinity of colonies that are able to ferment mannitol (such as those of pathogenic staphylococci). The color change is due to reduced pH caused by acidic byproducts of mannitol fermentation.

In which organism would you likely find a chlorosome?

Green sulfur bacteria Yes! Green sulfur bacteria contain chlorosomes. Chlorosomes, or chlorobium vesicles, house bacteriochlorophylls.

The reaction that is carried out by the enzyme catalase produces __________.

H2O and O2 The breakdown of hydrogen peroxide by catalase yields water (H2O) and oxygen gas (O2). The latter is responsible for the bubbling of wounds treated with hydrogen peroxide.

In green and purple bacteria, electrons to reduce CO2 can come from

H2S

Which of the following gases is or are produced during the breakdown of cysteine and methionine and is responsible for foul-smelling flatulence?

H2S The removal of sulfur from these sulfur-containing amino acids results in the liberation of the amino group (NH3) and the sulfur-group (H2S), resulting in the product pyruvate. The H2S gas is detectable due to its distinct odor.

Which of the following statements about fermentation is true?

It is an alternative way to return electron carriers to their oxidized state.

What is the fate of pyruvic acid in an organism that uses aerobic respiration?

It is converted into acetyl CoA.

Which of the following statements about photophosphorylation is FALSE?

It requires CO2.

What is the fate of the NAD+ newly regenerated by fermentation?

It returns to glycolysis to pick up more electrons.

What is the role of pyruvic acid in fermentation?

It takes the electrons from NADH, oxidizing it back into NAD+.

Which of the following is an acid produced by fermentation?

Lactic acid and propionic acid

How are Chemolithotrophs and Phototrophs Similar?

Many chemolithotrophs and phototrophs are also autotrophs.

Which of the following can be used as a final electron acceptor for aerobic respiration?

Molecular oxygen

Which compound is being reduced in the reaction shown in the figure?

NAD+

9. Why must NADH be reoxidized? How does this happen in an organism that uses respiration? Fermentation?

NAD+ is needed to pick up more electrons. NADH is usually reoxidized in respiration. NADH can be reoxidized in fermentation.

What will carry and give electrons to the ETC?

NADH, FADH2

From the list below, which is NOT produced during the Krebs cycle?

NADPH

6. A pastry chef accidentally inoculated a cream pie with six S. aureus cells. If S. aureus has a generation time of 60 minutes, how many cells would be in the cream pie after 7 hours?

Number of cells × 2n generations = Total number of cells 6×2^7=768

If high amounts of sulfanilamide are in the presence of an enzyme whose substrate is PABA, what outcome is expected?

PABA will not be catalyzed.

What is the key difference between photoheterotrophs and photoautotrophs?

Photoheterotrophs use organic compounds as their carbon source; photoautotrophs use carbon dioxide as their carbon source.

8. Write your own definition of the chemiosmotic mechanism of ATP generation. On Figure 5.16, mark the following using the appropriate letter: a) the acidic side of the membrane b) the side with a positive electrical charge c) potential energy d) kinetic energy

Protons are pumped from one side of the membrane to the other; transfer of protons back across the membrane generates ATP. a) the acidic side of the membrane and b) the side with a positive electrical charge. Outer portion is acidic and has a positive electrical charge c) potential energy. Energy-conserving sites are the three loci where protons are pumped out. d) kinetic energy. Kinetic energy is realized at ATP synthase.

How does the proton gradient help ATP synthase to make ATP?

Protons move from outside the membrane to inside the membrane.

Which of the following types of organisms uses hydrogen sulfide for reducing power?

Purple sulfur bacteria Yes! Purple sulfur bacteria employ anoxygenic photosynthesis with hydrogen gas, sulfur compounds such as hydrogen sulfide, or sulfur as an electron donor (reducing power) in photosynthesis.

How is pathogenic Staphylococcus aureus distinguished from other species of Staphylococcus?

Staphylococcus aureus is able to ferment mannitol, while other members of the genus are not. Staphylococcus aureus can be differentiated from other species of Staphylococcus, because it is able to ferment mannitol and thus causes mannitol salts agar to change color from red to yellow.

A key feature of cellular respiration is the removal of electrons from fuel molecules (oxidation) and the ultimate acceptance of these electrons by a low-energy electron acceptor. The process involves the use of electron carriers, NAD+ and FAD, which play crucial roles in multiple steps of the metabolic pathways. The overall equation for cell respiration is shown below. Why do NAD+ and FAD NOT appear in the overall equation? C6H12O6+6O2+38ADP+38Pi→6CO2+6H2O+38ATPC6H12O6+6O2+38ADP+38Pi→6CO2+6H2O+38ATP

The NAD+ and FAD are initially reduced then oxidized to their original state, so they do not appear in the net equation. At least 10 NAD+ and 2 FAD are used in the cellular respiration pathway. They pick up electrons during oxidation reactions in glycolysis, oxidation of pyruvate to form acetyl CoA, and the Krebs cycle, and then they give up these electrons to the electron transport chain. They don't appear in the net reaction equation because all of the NAD+ and FAD that enter into the reactions are oxidized back to their original form when they give up their electrons.

When bacteria are inoculated into a new sterile nutrient broth, their numbers don't begin to increase immediately. Instead, there is a lag phase that may last for an hour or even several days. Why don't bacterial numbers increase immediately?

The bacteria must adjust to the nutrient content in the new medium, synthesizing necessary amino acids, growth factors, and enzymes. A new medium may not have the same nutrients that were available in the medium from which an inoculum was taken. The bacteria may have to synthesize different amino acids, growth factors, or enzymes to enable them to grow in this new medium. Once those are synthesized, the growth rate is likely to increase, and the cells will move into log (exponential) growth phase.

Which of the following best describes the role of the gut microbiome in human digestion?

The gut microbiome breaks down dietary compounds that human metabolic enzymes cannot break down. The gut microbiome is an important component of our digestive system. It breaks down many compounds that our own digestive enzymes cannot handle. It also provides us with certain vitamins and assists our immune system.

The step that precedes the Krebs cycle in aerobic cellular respiration is?

The intermediate step Aerobic cellular respiration can be divided into four steps: glycolysis, the intermediate step, the Krebs cycle, the electron transport chain.

Which of the following is a trait unique to photosynthetic eukaryotes?

The presence of chloroplasts Yes! Chloroplasts are membrane-bound organelles, and thus unique to eukaryotes.

Microbes are often identified using biochemical tests that detect specific enzymes of metabolic pathways. E. coli typically ferments lactose, whereas Shigella does not. If a pure culture of each bacterium was placed in a tube containing lactose as the only food source, and a chemical indicator changed color after a pH change, what would the tubes look like after the bacteria were incubated?

The tube with E. coli would show a pH change, and the Shigella tube would show no change. This biochemical test is used to differentiate E. coli, which produces lactase and ferments the sugar (thereby producing acids), from Shigella, which does not produce lactase.

Which of the following statements regarding infections involving biofilms is FALSE?

There is no way to prevent biofilms from developing on surfaces. This is false. Antimicrobials can be applied to the surface of catheters and IV tubing to prevent biofilm development.

Which of the following best describes the effect of autoinducers as their concentration increases around bacterial cells?

They alter bacterial gene expression. Autoinducers are signaling molecules that bacteria use for quorum sensing. As the concentration of autoinducers increases, more and more bacterial receptors are activated. At some threshold level, the activated receptors cause changes in bacterial gene expression. These changes contribute to biofilm development, and may trigger increased virulence.

How does a competitive inhibitor slow enzyme catalysis?

They compete with the substrate for the enzyme's active site.

What is the limitation of these first three methods?

They will measure living and dead cells

What is the main function of fermentation?

To regenerate NAD+ for glycolysis. In the absence of O2, the electron carrier NADH accumulates, effectively lowering the available NAD+. Fermentation uses pyruvate and its derivatives to oxidize NADH to regenerate NAD+ for glycolysis.

Nitrogen-fixing bacteria, such as cyanobacteria, can use atmospheric nitrogen (N2) for their nitrogen source.

True

Cyanide is a poison that induces cell death by preventing the electron transport chain from functioning. Which of the below statements best describes how cyanide kills cells.

Without the movement of electrons through the electron transport chain, the hydrogen ion gradient is not produced, chemiosmosis will not occur. Without chemiosmosis, the cell is unable to produce enough cellular ATP to survive. Electron carriers donate electrons to the electron transport chain, and the energy released from these electrons is used to pump hydrogen ions across the plasma membrane. These hydrogen ions move back across the membrane through the transmembrane protein ATP synthase, which uses the energy from the hydrogen ion movement to produce ATP from ADP. Cyanide stops the electron transport chain, much like clogging a pipe, leaving the electrons stuck on their electron carriers. Without the movement of electrons through the electron transport chain, the hydrogen ion concentration is not created and thus they will not move through ATP synthase in chemiosmosis.

What is the most acidic place in the figure?

a

5. There are three mechanisms for the phosphorylation of ADP to produce ATP. Write the name of the mechanism that describes each of the reactions in the following table. ATP Generated by Reaction An electron, liberated from chlorophyll by light, is passed down an electron transport chain Cytochrome c passes two electrons to cytochrome a

a) Photophosphorylation b) Oxidative phosphorylation c) Substrate-level phosphorylation

1. Which substance in the following reaction is being reduced? Acetaldehyde->Ethanol a) acetaldehyde b) NADH c) ethanol d) NAD+

a) acetaldehyde

2. Medium 2 is a) selective. b) differential. c) both selective and differential.

a) selective.

Which of the follow are correctly matched with possible final electron acceptors?

aerobic respiration - O2, fermentation - pyruvate, fermentation - acetaldehyde , anaerobic respiration - CO2, anaerobic respiration - nitrate

In the figure, which line best depicts a facultative anaerobe in the absence of O2?

b

In the figure, which tube shows the expected growth pattern for a facultative anaerobe?

b

6. Which of the following is the best definition of respiration? a) a sequence of carrier molecules with O2 as the final electron acceptor b) a sequence of carrier molecules with the final electron acceptor from the environment c) a method of generating ATP d) the complete oxidation of glucose to CO2 and H2O e) a series of reactions in which pyruvic acid is oxidized to CO2 and H2O

b) a sequence of carrier molecules with the final electron acceptor from the environment

10. An organism that has peroxidase and superoxide dismutase but lacks catalase is most likely an a) aerobe. b) aerotolerant anaerobe. c) obligate anaerobe.

b) aerotolerant anaerobe.

3. Which of the following processes does not generate ATP? a) photophosphorylation b) the Calvin-Benson cycle c) oxidative phosphorylation d) substrate-level phosphorylation e) All of the above generate ATP

b) the Calvin-Benson cycle

Which biochemical process is NOT used during glycolysis?

beta oxidation

Patients with indwelling catheters (long-term tubes inserted into body orifices for drainage, such as through the urethra and into the urinary bladder) are susceptible to infections because

biofilms develop on catheters.

A bacterium that only possesses the ability to ferment obtains energy

by glycolysis only.

3. Which of the lines best depicts the log phase of a thermophile incubated at room temperature?

c

In the figure, which line best depicts an obligate anaerobe in the presence of O2?

c

In the figure, which line shows the growth of an obligate aerobe incubated anaerobically?

c

The figure shows a typical bacterial growth curve with the y-axis indicating the log of the number of bacteria and the x-axis indicating time in culture. In the figure, which section (or sections) shows a growth phase where the number of cells dying equals the number of cells dividing?

c

5. Which of the following is the best definition of the Krebs cycle? a) the oxidation of pyruvic acid b) the way cells produce CO2 c) a series of chemical reactions in which NADH is produced from the oxidation of pyruvic acid d) a method of producing ATP by phosphorylating ADP e) a series of chemical reactions in which ATP is produced from the oxidation of pyruvic acid

c) a series of chemical reactions in which NADH is produced from the oxidation of pyruvic acid

1. Medium 1 is a) selective. b) differential. c) both selective and differential.

c) both selective and differential.

4. Which of the following compounds has the greatest amount of energy for a cell? a) CO2 b) ATP c) glucose d) O2 e) lactic acid

c) glucose

8. Which of the following is not a characteristic of biofilms? a) antibiotic resistance b) hydrogel c) iron deficiency d) quorum sensing

c) iron deficiency

5. Assume you inoculated 100 facultatively anaerobic cells onto nutrient agar and incubated the plate aerobically. You then inoculated 100 cells of the same species onto nutrient agar and incubated the second plate anaerobically. After incubation for 24 hours, you should have a) more colonies on the aerobic plate. b) more colonies on the anaerobic plate. c) the same number of colonies on both plates.

c) the same number of colonies on both plates.

Which of the following uses CO2 for carbon and H2 for energy?

chemoautotroph

Which of the following uses glucose for carbon and energy?

chemoheterotroph

Which type of metabolic diversity contains most pathogens?

chemoheterotroph Chemoheterotrophs use organic molecules as a source of both energy and carbon. Inside a host, there will be lots of different organic molecules being transported around the body. Thus, the pathogen would need less energy to just steal these molecules than to make them as autotrophs do. Phototrophs use light as an energy source. Light is not present inside your body, so these organisms would not be able to perform photosynthesis and survive in your body.

Which group do human pathogens most likely belong? (Think about what they are using as food and energy sources)

chemoorganoheterotrophs (chemoheterotrophs)

A culture medium consisting of agar, peptone, and beef heart is a

complex medium

Refer to the figure. In aerobic respiration, where is water formed?

d

2. Which of the following reactions produces the most molecules of ATP during aerobic metabolism? a) glucose → glucose 6-phosphate b) phosphoenolpyruvic acid → pyruvic acid c) glucose → pyruvic acid d) acetyl CoA → CO2 + H2O e) succinic acid → fumaric acid

d) acetyl CoA → CO2 + H2O

6. The term trace elements refers to a) the elements CHONPS. b) vitamins. c) nitrogen, phosphorus, and sulfur. d) small mineral requirements. e) toxic substances.

d) small mineral requirements.

Which of the following is an advantage of the standard plate count?

determines the number of viable cells

The term aerotolerant anaerobe refers to an organism that

does not use oxygen but tolerates it.

What is the first step in binary fission?

duplication of the bacterial chromosome The bacterial cell duplicates its entire chromosome before division takes place. This ensures that each daughter cell has the full complement of information required to carry out its necessary functions.

In the figure, which tube shows the expected growth pattern for a microaerophile?

e

7. Which one of the following temperatures would most likely kill a mesophile? a) -50°C b) 0°C c) 9°C d) 37°C e) 60°C

e) 60°C

What type of growth is exhibited by bacteria?

exponential growth Bacterial populations double in number each generation, resulting in a rapid increase in cell numbers over a relatively short period of time.

Most antibiotics work best on actively growing bacteria. At which phase are bacteria most susceptible to the actions of these antibacterial drugs?

exponential growth phase Exponential growth represents the population of bacteria dividing at maximum efficiency. The inhibition of cell function works best on these actively growing cells.

Bacteria that can grow in the presence or absence of oxygen (O2) are called __________.

facultative anaerobes Facultative anaerobes are able to use oxygen if it is present but also grow in the absence of oxygen, although with decreased efficiency.

Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt?

facultative halophiles

Quorum sensing affects biofilm development through control of __________.

gene expression Quorum sensing is the process by which bacteria sense the density of nearby microorganisms. Bacteria respond to changes in this density of neighboring cells though changes in gene expression. These changes in gene expression lead to particular characteristics of the biofilm: matrix formation, water channels, and cooperative relationships with other bacterial species.

In cellular respiration of glucose, what are the three principal stages?

glycolysis, Krebs cycle, and the electron transport chain The glucose is split in glycolysis, and the products enter the Krebs cycle, in which they are further broken down. The process concludes with the harvesting of energy in the electron transport chain.

Salts and sugars work to preserve foods by creating a

hypertonic environment

Chemilithotroph

inorganic energy source

Match the nutritional group of Microbes with the BEST description. Phototroph

light energy source

Where is the generation time the lowest?

log (exponential) phase

Which of the following phases of the bacterial growth curve is matched with the correct definition?

log phase--the phase in which organisms are actively dividing and the generation time is constant This is the steep upward slope of the bacterial growth curve, where organisms are rapidly multiplying.

Microbes have very narrow optimum temperature ranges. Which of the following classifications of microbes are most likely to cause human disease, based on their temperature requirements?

mesophiles The temperature range of mesophiles overlaps that of normal human body temperature, allowing the greatest growth.

For which of the following types of microbes would a microbiologist employ living host cells to support their growth?

obligate intracellular organisms, such as chlamydias and rickettsias, and viruses These organisms cannot grow on media but require living host cells when cultured.

6. All of the energy-producing biochemical reactions that occur in cells, such as photophosphorylation and glycolysis, are ______ reactions.

oxidation

In the generation of ATP, energy is released when electrons are passed to a series of electron acceptors and finally to oxygen or another inorganic compound. What is this process called?

oxidative phosphorylation In oxidative phosphorylation, electrons are transferred from organic compounds to one group of electron carriers (usually NAD+ or FAD). Then, electrons are passed through a series of different electron carriers to molecules of oxygen or other oxidized inorganic and organic molecules. This process occurs in the plasma membrane of prokaryotes and in the inner mitochondrial membrane of eukaryotes. The sequence of electron carriers used in oxidative phosphorylation is called an electron transport chain (system). The transfer of electrons from one electron carrier to the next releases energy, some of which is used to generate ATP from ADP through a process called chemiosmosis.

All of the following are required in the reactions of microbial respiration EXCEPT

oxygen

You have just started brewing beer at home, and your first batch is now ready. You used the yeast Saccharomyces cerevisia, which can perform both aerobic cellular respiration and fermentation. When you test the beer, you determine that the alcohol content is almost zero. What could have been present in the fermentation reaction apparatus that caused this problem?

oxygen Cellular respiration is a much more efficient process than fermentation, meaning it produces more energy per glucose molecule (about 38 ATPs) than does fermentation (2 ATPs). If oxygen is present, then an organism that can perform both aerobic cellular respiration and fermentation will use cellular respiration to get as much energy from each glucose as possible. Fermentation produces the alcohol, the desired product in beer, but cellular respiration does not. When making alcoholic beverages, the conditions in the reaction apparatus must be anaerobic, so fermentation is used by the fermenting organism.

What is the difference between oxygenic and anoxygenic microbes?

oxygenic use H2O to replace a pigment's lost/excited electron; anoxygenic use something else as this e- source

Which organism is NOT correctly matched to its energy source?

photoautotroph - CO2

Which of the following has bacteriochlorophylls and uses alcohols for carbon?

photoheterotroph

This activity asks you to consider various methods of counting or estimating the size of bacterial populations and to select the method that will provide the most accurate data for plotting a bacterial growth curve. Which of the following methods would be most appropriate for gathering data to plot a bacterial growth curve throughout the four phases?

plate count A plate count will provide the number of living cells. These data are most appropriate for generating a plot of a bacterial growth curve.

In the figure, the path labeled "2" is the flow of

protons.

Which of the following actions would increase enzymatic activity in a bacterial cell that normally thrives in the human body?

slightly increasing the temperature within the optimum range Most chemical reactions increase with higher temperature within the optimum range because the molecules are moving faster.

Much of the energy released in catabolic reactions is captured in ATP for use in other reactions. When the phosphate is transferred directly from an organic molecule to ADP in order to produce ATP without an energized membrane, what has occurred?

substrate-level phosphorylationcyclic Correct. This is the case when the phosphate is transferred from a substrate to ADP.

Fatty acids are oxidized in

the Krebs cycle.

Which of the following is the best definition of generation time?

the length of time needed for a cell to divide

Which of the following pairs of microbe classification terms and optimal growth temperatures is mismatched?

thermophile - growth at 37°C

A bacterium such as Pseudomonas uses nitrate as a final electron acceptor in an electron transport system. All the below statements are true EXCEPT

they require light.

What is the purpose of fermentation?

to regenerate NAD+ from NADH After glucose has been broken down into pyruvic acid, the pyruvic acid can be completely broken down in cellular respiration, or it can be converted to an organic product in fermentation, whereupon NAD+ and NADP+ are regenerated and can enter another round of glycolysis.

Autotroph

uses carbon (CO2) fixation

Which of the following is an organic growth factor?

vitamin B1