Question 1

Which of the following uses glucose for carbon and energy?

Accepted Answer

Chemoheterotrophs use organic molecules such as glucose for both their carbon and energy source.

Question 2

If a cell is starved for ATP,which of the following pathways would most likely be shut down?

Accepted Answer

The pentose phosphate pathway is primarily involved in the production of NADPH and ribose-5-phosphate rather than ATP. If a cell is starved for ATP, it would prioritize pathways that generate ATP, like glycolysis and the Krebs cycle, and may downregulate pathways like the pentose phosphate pathway that do not directly contribute to ATP production.

Question 3

Figure 5.7 
-The graph at the left in Figure 5.7 shows the reaction rate for an enzyme at its optimum temperature.Which graph shows enzyme activity at a higher temperature?

Accepted Answer

Graph B shows higher enzyme activity at a higher temperature than the optimum temperature shown in Graph A. Graph C shows decreased enzyme activity due to denaturation at a very high temperature, and Graph D shows no enzyme activity at low temperatures.

Question 4

An enzyme,citrate synthase,in the Krebs cycle is inhibited by ATP.This is an example of all of the following EXCEPT

Accepted Answer

Citrate synthase inhibition by ATP is an example of allosteric inhibition (where the inhibitor binds to a site other than the active site), feedback inhibition (since ATP is a product of cellular respiration, its abundance signals the cell to slow down the Krebs cycle), and noncompetitive inhibition (as the inhibitor does not compete with the substrate for the active site). It is not an example of competitive inhibition, where the inhibitor would compete directly with the substrate for binding to the active site.

Question 5

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

Accepted Answer

Green and purple bacteria are anaerobic organisms that can use a variety of electron donors for photosynthesis. In these bacteria, electrons to reduce CO₂ can come from H₂S (hydrogen sulfide) instead of H₂O, which is used in oxygenic photosynthesis. This process is called anoxygenic photosynthesis. Choice A, B, and C are incorrect because they are electron acceptors, not donors. Choice E is incorrect because chlorophyll is a pigment that absorbs light energy, not a source of electrons.

Question 6

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.

Accepted Answer

2- ATP acts as a common intermediary molecule that transfers energy between catabolic (energy-releasing) and anabolic (energy-consuming) pathways, facilitating the flow of energy within cells.4- Anaerobic organisms, which do not require oxygen for growth, can indeed generate ATP through processes such as anaerobic respiration or fermentation.5- The generation of ATP by the flow of protons (H+) across protein channels in a membrane is a fundamental process in both photosynthesis and cellular respiration, known as chemiosmosis.

Question 7

Assume you are working for a chemical company and are responsible for growing a yeast culture that produces ethanol.The yeasts are growing well on the maltose medium but are not producing alcohol.What is the most likely explanation?

Accepted Answer

Yeasts require anaerobic conditions for ethanol production, so the presence of oxygen in the medium will prevent the production of ethanol.

Question 8

Which of the following statements regarding the glycolysis pathway is FALSE?

Accepted Answer

In the glycolysis pathway, two molecules of ATP are expended, not just one. This occurs in the early steps of glycolysis to phosphorylate glucose and fructose-6-phosphate.

Question 9

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

Accepted Answer

Pseudomonas bacteria do not require light for respiration. The other statements are true - nitrate serves as a final electron acceptor, but the process does not yield as much ATP as oxygen as a final electron acceptor, they can respire without O₂, and the process produces nitrite ion. The process also requires an electron donor, as stated in option E.

Question 10

Which of the following statements regarding metabolism is FALSE?

Accepted Answer

Anabolic reactions are constructive (build-up) and require energy input, while catabolic reactions are degradative and release energy. Therefore, statement D is false. Heat may be released in both types of reactions (A), and ATP is formed in catabolic reactions while ADP is formed in anabolic reactions (B and C).

Question 11

Microorganisms that catabolize sugars into ethanol and hydrogen gas would most likely be categorized as

Accepted Answer

The answer of Microorganisms that catabolize sugars into ethanol and...

Question 12

Assume you are growing bacteria on a lipid medium that started at pH 7.The action of bacterial lipases should cause the pH of the medium to

Accepted Answer

Bacterial lipases break down lipids into fatty acids and glycerol. Fatty acids are acidic in nature, and their release into the medium will cause the pH to decrease (become more acidic).

Question 13

Which of the following statements regarding the Entner-Doudoroff pathway is TRUE?

Accepted Answer

The Entner-Doudoroff pathway is an alternative pathway to glycolysis that is found in some bacteria. It involves the oxidation of glucose to pyruvate, and generates NADH and ATP.

Question 14

Figure 5.8
 
-In Figure 5.8,where is ATP produced?

Accepted Answer

The answer of Figure 5.8
 
-In Figure 5.8,where is ATP...

Question 15

Gallionella bacteria can get energy from the reaction Fe²⁺ → Fe³⁺.This reaction is an example of

Accepted Answer

The reaction Fe²⁺ → Fe³⁺ involves the loss of electrons, which is characteristic of oxidation.

Question 16

Figure 5.6 
-The rates of O₂ and glucose consumption by a bacterial culture are shown in Figure 5.6.Assume a bacterial culture was grown in a glucose medium without O₂.Then O₂ was added at the time marked X.The data indicate that

Accepted Answer

The graph shows that before time X, the bacteria were consuming glucose without the presence of O₂. After time X, when O₂ was added, the rate of glucose consumption increased, indicating that the bacteria switched to aerobic metabolism. This suggests that the bacteria can use both anaerobic fermentation and aerobic metabolism for energy production, but the latter is more efficient. Therefore, choice C is the correct answer.

Question 17

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

Accepted Answer

Photoheterotrophs are organisms that utilize light for energy but cannot use carbon dioxide as their sole carbon source. Instead, they use organic compounds, which can include alcohols. Bacteriochlorophylls are pigments found in certain photosynthetic bacteria, allowing them to capture light energy, which aligns with the characteristics of photoheterotrophs.

Question 18

Cyanobacteria are a type of

Accepted Answer

Cyanobacteria are photosynthetic organisms, which means they use light energy to produce organic compounds from inorganic nutrients like water and carbon dioxide. Therefore, they are classified as photoautotrophs.

Question 19

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

Accepted Answer

Chemoautotrophs use CO₂ as their carbon source and use chemicals such as H₂ as their energy source.

Question 20

A bacterial culture grown in a glucose-peptide medium causes the pH to increase.The bacteria are most likely

Accepted Answer

When bacteria use peptides (amino acids) for energy, they often deaminate them, releasing ammonia (NH3) which increases the pH of the medium. This is in contrast to fermentation or oxidation of glucose, which typically produces acidic byproducts, lowering the pH.

Quiz 5: Microbial Metabolism