Mastering Micro Ch5

Catabolic reactions are generally degradative and hydrolytic.

True

Once an enzyme has converted substrates into products, the active site reverts back to its original form.

True

A reaction that involves the transfer of electrons from one molecule to another is referred to as

a redox reaction.

A strictly fermentative bacterium produces energy

by glycolysis only

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

heterolactic fermenters.

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

oxidation

Which of the following is NOT necessary for respiration?

oxygen

Which organism is NOT correctly matched to its energy source?

photoautotroph - CO2

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.

Which of the following statements regarding metabolism is FALSE?

Anabolic reactions are degradative.

Which of the following statements regarding competitive inhibitors is true?

Competitive inhibitors decrease the rate of enzyme activity.

Compare and contrast three metabolic pathways by choosing whether the statement applies to fermentation. Check all that apply.

End products may include lactic acid or ethanol. Process includes glycolysis. Can generate ATP in the absence of O2. A total of 2 ATP are produced per molecule of glucose input. The coenzyme NAD+ plays an important role in the pathway.

Why do all enzymatic reactions need activation energy?

Energy is required to disrupt a substrate's stable electron configuration.

Why are enzymes important to biological systems?

Enzymes decrease the amount of activation energy required for chemical reactions to occur.

What is meant by the statement "Enzymes are biological catalysts"?

Enzymes speed up the chemical reactions in living cells.

The use of enzymes is necessary to increase the activation energy requirements of a chemical reaction.

False

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

Glucose is the original electron donor. More ATP is formed than is consumed in this process. Glyceraldehyde 3- phosphate is oxidized, and NAD+ is reduced to NADH. The 6-carbon skeleton of glucose is enzymatically split into two 3- carbon compounds.

Which of the following statements about anaerobic respiration is FALSE?

It involves the reduction of an organic final electron acceptor.

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

It is converted into acetyl CoA.

Which compound is being reduced in the reaction shown in the figure? (multiple choice question 2)

NAD+

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

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

PABA products will increase concentration.

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? C 6 H 12 O 6 +6 O 2 +38ADP+38 P i →6C O 2 +6 H 2 O+38ATP

The NAD+ and FAD are initially reduced then oxidized to their original state, so they do not appear in the net equation.

The P. multocida that are growing within Sam's abscess are breaking glucose down via glycolysis in order to obtain energy. This process occurs via a series of enzymatic reactions. During a chemical reaction, an enzyme functions as a biological catalyst and lowers the activation energy. How does an enzyme lower the activation energy of a reaction?

The enzyme increases the effectiveness of reactant collisions thereby increasing the number of reactant molecules that reach activation energy.

Which of the following is TRUE about this reaction? NO3-+ 2H+ NO2- + H2O Nitrate ion Nitrite ion

This process occurs anaerobically.

Which type of reaction is in the figure? (the one with aspartic acid, alpha ketoglutaric acid, glutamic acid, and oxaloacetic acid)

Transanimation

Refer to the figure. In aerobic respiration, where is water formed? (multiple choice question 41)

d

In the figure, where is ATP produced? (multiple choice question 40)

e

The pentose phosphate pathway can be characterized as an anabolic pathway.

false

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

In the figure, the path labeled "2" is the flow of (multiple choice question 43)

protons.

During an oxidation reaction,

the donor molecule loses an electron and becomes oxidized.

Which of the following is the best definition of fermentation?

the partial oxidation of glucose with organic molecules serving as electron acceptors

The advantage of the pentose phosphate pathway is that it produces all of the following EXCEPT

three ATPs.

What is the purpose of fermentation?

to regenerate NAD+ from NADH

An apoenzyme that loses its coenzyme subunit will be non-functional.

true

Glycolysis is utilized by cells in both respiration and fermentation.

true

In order for P. multocida to survive and carry out cellular functions (and cause infection), the energy contained in each molecule of glucose must be converted into ATP. This occurs via the process of chemiosmosis, which couples electron transport to ATP synthesis. This process involves the sequential transfer of elections via a series of protein complexes and carriers found in the bacterial plasma membrane. Recall that electrons move down the chain in a sequential fashion due to the increasing electronegativity of the components of the electron transport chain. Arrange the components of the electron transport chain in order from least electronegative to most electronegative thereby indicating the path of electrons through the electron transport chain.

(least to most) NADH dehydrogenase Coenzyme Q Cytochrome b-c1 complex Cytochrome c Cytochrome oxidase complex O2

Place the major steps of cellular respiration in order by dragging the appropriate figure to each box.

1) the one with glucose in the pic (glycolysis) 2)the one that starts w/ acetyl coA (Krebs cycle) 3) the one with the electrons in the middle (ETC)

Which statements correspond to amphibolic pathways? 1. anabolic and catabolic reactions are joined through common intermediate 2. shared metabolic pathways 3. Feedback inhibition can help regulate rates of reactions 4. both types of reactions are necessary but do not occur simultaneously

1, 2, 3

Match the words in the left column to the appropriate blanks in the sentences on the right. Words will be used more than once.

1. catabolic pathways break down macromolecules into simple component parts. 2. catabolic pathways release energy. 3. anabolic pathways build up macromolecules by combining simpler molecules. 4. anabolic pathways require energy. 5. catabolic pathways provide the building blocks and the energy needed for anabolic reactions. 6. Some energy released by catabolic reactions is stored in the form of chemical bonds in ATP. 7. catabolic reactions couple with ATP synthesis. 8. anabolic reactions couple with ATP breakdown.

Which of the following statements are true? (multiple choice question 27)

2, 4, 5

During the infection, there are many different environments that P. multocida will encounter. In order to cause an infection like the one in Sam's forearm, P. multocida must regulate its metabolic pathways in order to adapt to the changing environments. The process of glycolysis is regulated at several steps by allosteric inhibition. Which of the following are features of allosteric inhibition?

Allosteric inhibition can be irreversible. Allosteric inhibition can be reversed. The allosteric inhibitor binds to a site distinct from the active site resulting in decreased affinity of the enzyme for the substrate.

What enables competitive inhibitors to bind to a specific enzyme?

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

In this activity, you will be asked to examine the illustration above and determine whether each of a series of statements correctly describes the process. Sort the statements into the appropriate bin depending on whether they correctly or incorrectly describe some aspect of the electron transport chain and chemiosmosis.

Correct statements: The final electron acceptor is O2. A chemical that inactivates cytochrome c so that it can't pass electrons on to cytochrom a would block electron transport and ATP synthesis. The pH of the intermembrane space in the mitochondria would be lower than the pH of the mitochondrial matrix in an actively metabolizing cell. A toxin that causes a leak to form in the inner mitochondrial membrane such that protons could bypass the ATP synthase would prevent oxidative phosphorylation. Incorrect statements: Electrons moving from the FMN to Q to cytochrome b are gaining energy. ATP serves as an electron carrier in the electron transport chain. A toxin that causes a leak to form in the inner mitochondrial membrane such that protons could bypass the ATP synthase would disrupt the flow of electrons to O2. The electrons carried by FADH2 have more potential energy than those carried by NADH.

All organisms use oxidation-reduction reactions to harness energy, and this newly harvested energy is used to produce ATP. Oxidation is defined as the loss of electrons. Reduction is the gain of electrons. The energy in fuel molecules (often carbohydrates) is in the form of electrons. When electrons are removed from their high-energy state in fuel molecules (the electron donors), those molecules are oxidized. The electrons must be added to another molecule, which serves as the electron acceptor. As it gains electrons, the electron acceptor is reduced. When these electrons arrive at the final electron acceptor, they are at a lower-energy state compared to their original position in the electron donor. The goal is to harness the energy the electrons lose during this transfer process. In this activity, you will examine three equations and indicate which reactants are electron donors and which are receptors. In addition, you will identify the oxidized product and the reduced product. The image below shows three different oxidation-reduction equations. Sort each of the lettered items on the image into the proper bin.

Electron donors: e, a, i Electron acceptors: f, b, j Oxidized product: g, c, k Reduced products: h, d, l

At the doctor's office, the doctor drains the abscess and takes a sample for culturing. She also prescribes some broad-spectrum antibiotics to treat the obvious infection. A couple days later, the doctor tells Sam that his wound contained a number of bacteria including Pasteurella multocida. When the dog bit Sam's arm P. multocida entered the wound and started to establish an infection. In order to do so, the bacteria have to grow, which requires energy. One of the most common energy sources used by bacteria is glucose. Why is glucose such a good source of energy for bacteria?

Glucose is a highly reduced compound, containing many carbon-hydrogen bonds and a lot of potential energy.

How would a noncompetitive inhibitor interfere with a reaction involving the enzyme shown in the figure?

It would bind to b.

A urease test is used to identify Mycobacterium tuberculosis because

M. tuberculosis produces urease.

Which one of the following would you predict is an allosteric inhibitor of the Krebs cycle enzyme, α-ketoglutarate dehydrogenase?

NADH

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?

O2 is in the medium.

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

One molecule of ATP is expended.

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

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

Which of the following statements regarding redox reactions is true?

Redox reactions involve an oxidation reaction coupled with a reduction reaction.

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

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

Why is reduction the term used to describe the gain of an electron?

The electron acceptor's net charge decreases.

One of the environmental changes that P. multocida encounters during infection is the limitation of nutrients and oxygen. One of the changes that P. multocida (a facultative anaerobe) makes in this environment is to switch to anaerobic metabolism. Predict which of the following is most likely to occur as a result of the switch from aerobic to anaerobic metabolism.

The organisms will grow more slowly because they will produce less ATP compared to aerobic metabolism.

Which of the following statements about substrate-level phosphorylation is FALSE?

The oxidation of intermediate metabolic compounds releases energy that is used to generate ATP.

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.

There are five oxidation-reduction reactions depicted. The equivalent of one ATP is made for each turn of the Krebs cycle. The oxaloacetic acid that accepts the acetyl group is regenerated, enabling the cyclic nature of this process. The potential energy in the pyruvate is transferred to coenzymes NAD+ and FAD. Carbons from pyruvic acid end up as CO2. It takes two "turns" of the Krebs cycle to process the pyruvic acid molecules resulting from the glycolysis of one glucose molecule.

How does a competitive inhibitor slow enzyme catalysis?

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

In general, ATP is generated in catabolic pathways and expended in anabolic pathways.

True

What is the most acidic place in the figure? (multiple choice question 44)

a

In the figure, the structure labeled "1" is (multiple choice question 42)

a plasma membrane.

The rates of O2 and glucose consumption by a bacterial culture are shown in the figure. 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 (multiple choice question 33)

aerobic metabolism is more efficient than fermentation.

The graph at the left in the figure shows the reaction rate for an enzyme at its optimum temperature. Which graph shows enzyme activity at a higher temperature? (multiple choice question 37)

b

Which of the graphs in the figure best illustrates the activity of an enzyme that is saturated with substrate? (multiple choice question 10)

c

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

Which of the following compounds is NOT an enzyme?

coenzyme A

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

competitive inhibition.

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

pentose phosphate pathway

How is ATP generated in the reaction shown in the figure? (multiple choice question 8)

substrate-level phosphorylation