Which of the listed statements describes the results of the following reaction?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
C) C6H12O6 is oxidized and O2 is reduced
Which of the following statements about NAD+ is true?
D) NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes ___.
D) reduced
Glycolysis is __.
B) The process of oxidation of glucose into two molecules of pyruvate
In glycolysis, for each molecule of glucose oxidized to pyruvate ___.
D) two molecules of ATP are used and four molecules of ATP are produced
The free energy for the oxidation of glucose to CO2 and water is -686 kcal/mol and the free energy for the reduction of NAD+ to NADH is +53kcal/mol. Why are only two molecules of NADH formed during glycolysis when it appears that as many as a dozen could be formed?
A) Most of the free energy available from the oxidation of glucose remains in pyruvate, one of the products of glycolysis
The type of enzyme that adds a phosphate to its substrate is referred to as a ___.
A) kinase
The first step of glycolysis expends energy through the addition of phosphate to glucose, resulting in glucose-6-phosphate. Which of these enzymes is most likely responsible for catalyzing this reaction?
C) Hexokinase
What is the difference between the citric acid cycle, the TCA cycle, and the Krebs cycle?
A) These names all refer to the same process
In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to co-enzyme A
The three listed steps result in the formation of __.
B) acetyl CoA, NADH, and CO2
___ is the initial substrate of the TCA cycle, and ___ is the final product of the TCA cycle.
A) Acetly CoA; Oxaloacetate
Which of these is not a substrate of the citric acid cycle (TCA cycle)?
D) Glucose
If glucose is the sole energy source, what fraction of the carbon dioxide exhaled by animals is generated by the reactions of the citric acid cycle?
B) 2/3
In chemiosmosis, what is the most direct source of energy that is used to convert ADP + i to ATP?
B) Energy released from movement of protons through ATP synthase, down their electrochemical gradient
The synthesis of ATP by oxidative phosphorylation, using the energy released by movement of protons across the membrane down their electrochemical gradient, is an example of ___.
B) an endergonic reaction coupled to an exergonic reaction
Following glycolysis and the citric acid cycle, but before the electron transport chain and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to CO2 with some net gain of ATP. Most of the energy from the original glucose molecule at that point in the process, however, is in the form of ___.
B) NADH
Chemiosmotic ATP synthesis (oxidative phosphorylation) occurs in ___.
B) all respiring cells, both prokaryotic and eukaryotic, using either oxygen or other electron acceptors
Exposing the inner motochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." The little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP.
After the disruption, when electron transfer and ATP synthesis still occur, what must be present?
A) All of the electron transport proteins and ATP synthase
A young dog has never had much energy. He is brought to a veterinarian for help and she decides to conduct several diagnostic tests. She discovers that the dog's mitochondria can use only fatty acids and amino acids for respiration, and his cells produce more lactate than normal. Of the following, which is the best explanation of the dog's condition?
D) His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane
The oxidation of a molecule of glucose (a 6-carbon sugar) results in two molecules of pyruvate, or 2 molecules of acetyl CoA. During the oxidation of glucose, 2 carbons are lost and only 4 are able to enter the TCA cycle as acetyl CoA. By comparison, the beta oxidation of fatty acids breaks fatty acids into 2-carbon units, which are each used to generate acetyl CoA
B) A 12-carbon fatty acid
Even though plants cells photosynthesize, they still use their mitochondria for oxidation of pyruvate. This will occur in __.
A) all cells all the time
Which of the following normally occurs regardless of whether or not oxygen (O2) is present?
A) Glycolysis
One function of both alcohol fermentation and lactic acid fermentation is to __.
D) oxidize NADH to NAD+
A cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen when an athlete exhausts his or her ATP supply?
D) Catabolic processes are activated that generate more ATP
Approximately how many molecules of ATP are produced from the complete oxidation of one molecule of glucose (C6H12O6) in aerobic cellular respiration?
B) Around 36
Carbohydrates and fats are considered high-energy foods because they ___.
A) have a lot of electrons associated with hydrogen
The oxygen consumed during cellular respiration is involved directly in which process or event?
C) Accepting electrons at the end of the electron transport chain
When electrons move closer to a more electronegative atom, what happens? The more electronegative atom is ___.
A) reduced, and energy is released
In the initial "energy investment" stage of glycolysis, which enzymes are responsible for using ATP to transfer a phosphate to glucose (or its derivatives)?
C) Kinases
___ is/ are the starting substrate and ___ is/are the end product of the glycolysis pathway
B) 1 molecule of glucose; 2 molecules of pyruvate
Which electron carrier(s) function in the citric acid cycle?
D) NADH and FADH2
In the presence of oxygen, the three-carbon compound pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A.
Which one of the following is formed by the removal of a carbon (as CO2) from a molecule of pyruvate?
D) acetyl CoA
Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?
B) Mitochondrial intermembrane space
When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the
C) creation of a proton-motive force
The electron transport chain ___.
C) is a series of redox reactions
You have a friend who lost 7 kg (about 15 pounds) of fat on a regimen of strict diet and exercise. How did the fat leave his body?
B) It was released as CO2 and H2O
In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of __.
A) ATP, CO2, and ethanol (ethyl alcohol)
Why is glycolysis considered to be one of the first metabolic pathways to have evolved?
D) It does not involve organelles or specialized structures, does not require oxygen, and is present in most organisms.
The electron transport chain can use a single molecule of NADH to generate 3 ATPs and a single molecule of FADH2 to generate 2 ATPs. Imagine that you have a single glucose molecule. How many ATPs would be generated per molecule of acetyl CoA that enters the TCA cycle (following oxidation of one glucose molecule), if you only count ATP generated from NADH or FADH2 in the electron transport chain? For this question, use only NADH and FADH2 that is generated through the TCA cycle.
D) 22
The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction ___.
D) loses electrons and loses potential energy
What is the oxidizing agent in the following reaction?
Pyruvate + NADH + H+ → Lactate + NAD+
A) Pyruvate
Glycolysis is active when cellular energy levels are ___; the regulatory enzyme, phosphofructokinase, is __ by ATP
A) low; inhibited
Which of the following is not true of glycolysis?
A) Glycolysis requires O2
During the second phase of glycolysis, where energy is "generated", which type of enzyme uses the reduction of NAD+ to NADH in order to "store" energy?
A) Dehydrogenases
If pyruvate oxidation is blocked, what will happen to the levels of oxaloacetate and citric acid in the citric acid cycle?
A) Oxaloacetate will accumulate and citric acid will decrease
Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?
B) Oxidation of pyruvate to acetyl CoA and the citric acid cycle
Starting with citrate, which of the following combinations of products would result form three acetyl CoA molecules entering the citric acid cycle?
C) 3 ATP, 6 CO2, 9 NADH, and 3 FADH2
Which of the following events takes place in the electron transport chain?
D) The extraction of energy from high-energy elecytrons remaining from glycolysis and the citric acid cycle
The oxidation of a molecule of glucose (a 6-carbon sugar) results in two molecules of pyruvate, or 2 molecules of acetyl CoA. During the oxidation of glucose, 2 carbons are lost and only 4 are able to enter the TCA cycle as acetyl CoA. By comparison, the beta oxidation of fatty acids breaks fatty acids into 2-carbon units, which are each used to generate acetyl CoA.
Based on this information, which of these starting molecules would produce the most ATP if completely oxidized by a eukaryotic cell and used to drive oxidative phosphorylation of ATP?
A) 3 molecules of glucose and one molecule of a 12-carbon fatty acid have the same useable amount of carbons to make acetyl CoA, so they would be basically the same
In respiration, beta oxidation involves the ___.
D) breakdown of fatty acids
Yeast cells that have defective mitochondria incapable of respiration will be able to grow by catabolizing which of the following carbon sources for energy?
A) Glucose
High levels of citric acid inhibit the enzyme phosphofructokinase, a key in enzyme glycolysis. Citric acid binds to the enzyme at a different location from the active site. This is an example of ___.
D) allosteric regulation
If a cell is able to synthesize 30 ATP molecules for each molecule of glucose completely oxidized to carbon dioxide and water, approximately how many ATP molecules can the cell synthesize for each molecule or pyruvate oxidized to carbon dioxide and water?
