Mastering Microbiology Ch 5

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.

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

a redox reaction.

What is the purpose of fermentation?

to regenerate NAD+ from NADH

Which type of metabolic diversity contains most pathogens?

chemoheterotroph

During an oxidation reaction,

the donor molecule loses an electron and becomes oxidized.

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

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. The coenzyme NAD+ plays an important role in the pathway. Process includes glycolysis Can generate ATP in the absence of O2. A total of 2 ATP are produced per molecule of glucose input.

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.

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.

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

Glyceraldehyde 3-phosphate is oxidized, and NAD+ is reduced to NADH. 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.

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.

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

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. Can generate ATP in the absence of O2. Between 2 and 38 ATP are produced per molecule of glucose input. Process involves electron transport and chemiosmosis Process involves the Krebs cycle

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

Process involves the Krebs cycle End products are CO2 and H2O Process involves electron transport and chemiosmosis A total of 38 ATP are produced per molecule of glucose input. 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

Which of the following statements regarding redox reactions is true?

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

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+38ATP

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

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

The electron acceptor's net charge decreases

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.

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 equivalent of one ATP is made for each turn of the Krebs cycle. 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. The oxaloacetic acid that accepts the acetyl group is regenerated, enabling the cyclic nature of this process. There are five oxidation-reduction reactions depicted. The potential energy in the pyruvate is transferred to coenzymes NAD+ and FAD.

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.

How does a competitive inhibitor slow enzyme catalysis?

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

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

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