Question 1

How many acetyl-coA molecules may be obtained from oxidation of an 18-carbon fatty acid?

Accepted Answer

The oxidation of an 18-carbon fatty acid yields 9 acetyl-CoA molecules, as each acetyl-CoA consists of 2 carbons, and 18 divided by 2 equals 9.

Question 2

What is the first product of fatty acid catabolism?

Accepted Answer

The first product of fatty acid catabolism is acetyl-CoA, which is produced through beta-oxidation of the fatty acid chain. Glycerol is produced during the breakdown of triglycerides, but it is not the first product of fatty acid catabolism. Pyruvate is a product of glycolysis, which is a separate metabolic pathway from fatty acid catabolism. Triglycerides are the storage form of fats, and they are broken down into fatty acids and glycerol before undergoing beta-oxidation to produce acetyl-CoA.

Question 3

In a triglyceride that contains 54 carbon atoms, how many can become part of glucose?

Accepted Answer

The answer of In a triglyceride that contains 54 carbon...

Question 4

Which of the following is an aspect of glycolysis?

Accepted Answer

Glycolysis is the process of breaking down glucose into pyruvate molecules. It is a universal metabolic pathway among living organisms and occurs in both aerobic and anaerobic conditions. Glycolysis is a series of 10 enzymatic reactions that generate ATP and NADH. One molecule of glucose generates two molecules of pyruvate. Therefore, choice D is correct. Choices A and B are incorrect because glycolysis is reversible and can occur in both the presence and absence of oxygen.

Question 5

In which of the following groups can all of the dietary components be used to synthesize and store glycogen?

Accepted Answer

Wheat starch can be used to synthesize and store glycogen through the process of glycogenesis. Plant proteins can be broken down into constituent amino acids, some of which can be converted to glucose through gluconeogenesis, and subsequently stored as glycogen. Lactose, while a source of glucose, is not typically converted to glycogen.

Question 6

Which of the following is a possible fate of acetyl-coA?

Accepted Answer

Acetyl-coA can be used in the synthesis of fatty acids through the process of fatty acid biosynthesis.

Question 7

What percentage (by weight) of a triglyceride molecule can be converted to glucose?

Accepted Answer

The answer of What percentage (by weight) of a triglyceride...

Question 8

The series of reactions involving the conversion of glucose to pyruvate is known as which of the following?

Accepted Answer

The series of reactions involving the conversion of glucose to pyruvate is known as glycolysis. Pyrolysis is a thermal decomposition reaction, beta-oxidation is the breakdown of fatty acids, and a coupled reaction involves the simultaneous occurrence of two or more chemical reactions.

Question 9

Which of the following nutrients can be made from compounds composed of 2-carbon skeletons?

Accepted Answer

Fatty acids can be synthesized from compounds composed of 2-carbon skeletons through the process of beta-oxidation. Glucose, fructose, and glycogen require longer carbon-chain compounds for their synthesis.

Question 10

Which of the following pathways from pyruvate is irreversible?

Accepted Answer

The conversion of pyruvate to acetyl CoA by the enzyme pyruvate dehydrogenase is irreversible, as it is a highly exergonic reaction and there is no pathway to convert acetyl CoA back to pyruvate. The other options listed (A, B, and C) all involve reversible reactions.

Question 11

Which of the following distinguishes aerobic metabolism from anaerobic metabolism?

Accepted Answer

Aerobic metabolism produces energy more slowly but more efficiently than anaerobic metabolism, utilizing oxygen to break down glucose and generate ATP, the energy currency of the cell.

Question 12

The Cori cycle involves the interconversion of which of the following pairs?

Accepted Answer

The Cori cycle involves the conversion of lactate produced by muscle tissues during anaerobic respiration to glucose in the liver. The liver then sends this glucose back to the muscle tissues for use in aerobic respiration. This cycle is important in allowing muscles to continue functioning during periods of intense exercise when oxygen availability may be limited.

Question 13

Fatty acid oxidation results in the direct production of which of these compounds?

Accepted Answer

Fatty acid oxidation (also known as beta-oxidation) results in the direct production of acetyl-coA through a series of enzymatic reactions in the mitochondria. This acetyl-coA can then be used in the Krebs cycle to generate ATP. Choice A is incorrect because ketones are produced as a result of the breakdown of fatty acids in the liver during periods of prolonged fasting or starvation. Choice B is incorrect because fructose is a sugar, not a product of fatty acid oxidation. Choice C is incorrect because pyruvate is a product of glycolysis, not fatty acid oxidation.

Question 14

An aerobic reaction is one that requires which of the following components?

Accepted Answer

An aerobic reaction requires oxygen.

Question 15

Production of excessive amounts of acetyl-coA molecules leads to the synthesis of which of the following compounds?

Accepted Answer

Excessive amounts of acetyl-CoA molecules are primarily used for the synthesis of fatty acids in the process of fatty acid synthesis or lipogenesis. While glucose and amino acids can also be converted to acetyl-CoA and used for fatty acid synthesis, fructose is not a significant source of acetyl-CoA.

Question 16

Which of the following groups contains only compounds that can be formed from metabolized glucose?

Accepted Answer

Acetyl CoA can be formed from the breakdown of glucose through the process of glycolysis and subsequent conversion of pyruvate to acetyl CoA. Amino acids can also be metabolized from glucose through various pathways such as gluconeogenesis and the synthesis of non-essential amino acids. Muscle glycogen is a storage form of glucose in muscle tissue and can be broken down into glucose to be metabolized. Urea and ammonia are not forms of glucose or derivatives of glucose metabolism. Therefore, choice B contains only compounds that can be formed from metabolized glucose.

Question 17

When a person is performing intense physical exercise and begins to feel fatigue and a burning pain in the muscles, the response of the muscles is to synthesize more of which of the following compounds?

Accepted Answer

When muscles undergo intense physical exercise, they rely heavily on anaerobic respiration, which uses glucose as a fuel source and produces lactate as a byproduct. As lactate accumulates in the muscles, it causes a burning pain and fatigue sensation. However, the muscles respond by synthesizing more lactate, which serves as an important energy source during high-intensity exercise. Glucose and fatty acids can also be used as fuel sources, but lactate synthesis is the primary response to muscle fatigue and burning. Citric acid is not directly involved in muscle contraction or energy production but plays a central role in the aerobic respiration process that occurs after the exercise is complete.

Question 18

Which of the following series outlines the overall sequence of events in the complete oxidation of glucose?

Accepted Answer

The overall sequence of events in the complete oxidation of glucose is glycolysis, TCA cycle, and electron transport chain. The Cori cycle is not a part of the sequence of events for glucose oxidation. Option B presents the correct sequence of events.

Question 19

Your roommate Demetrius is participating in a weightlifting course and complains of a burning pain during workouts. You explain to Demetrius that this is due to his muscles converting excess pyruvate to which of the following compounds?

Accepted Answer

During high-intensity exercise, the body may not be able to provide enough oxygen to the muscles to support aerobic respiration. Instead, the muscles rely on anaerobic respiration to produce ATP. This process produces excess pyruvate, which is converted to lactate to prevent a buildup of acidic compounds in the cells. The burning sensation felt during exercise is due to the buildup of lactate in the muscles.

Question 20

Approximately what percentage of the weight of triglycerides can be converted to glucose?

Accepted Answer

Approximately 5 percent of the weight of triglycerides can be converted to glucose. This is because only the glycerol portion of triglycerides can be converted into glucose through gluconeogenesis, and glycerol makes up about 5% of the weight of triglycerides. The fatty acid portion cannot be converted into glucose.

Quiz 7: Metabolism: Transformations and Interactions