Metabolism
What is the role of NAD+ in the process of cellular respiration?
electron carrier
Which of the following molecules is NOT a product of glycolysis?
A. ATP
B. FADH2
C. NADH
D. Pyruvate
B. FADH2
Where does pyruvate oxidation occur in the cell?
matrix of mitochondria
What is the final molecule regenerated to allow the Krebs cycle to continue?
oxaloacetate
What molecule is the final acceptor of electrons at the end of the electron transport system in aerobic cellular respiration?
oxygen
During cellular respiration, NAD⁺ accepts electrons and becomes NADH. Which statement BEST describes this process?
A. NAD⁺ is reduced because it gains electrons.
B. NAD⁺ is oxidized because it loses electrons.
C. NADH is oxidized because it gains electrons.
D. NADH is reduced because it loses electrons.
A. NAD⁺ is reduced because it gains electrons.
Which of the following processes is a result of glycolysis?
A. production of CO2
B. oxidation of NADH to NAD+
C. reduction of FAD to FADH2
D. phosphorylation of ADP to form ATP
D. phosphorylation of ADP to form ATP
What molecule does pyruvate become after oxidation?
acetyl-CoA
Which of the following statements CORRECTLY describes the citric acid cycle?
A. It uses O2 as an electron acceptor.
B. It produces two NADH per glucose molecule.
C. It produces ATP via oxidative phosphorylation.
D. It uses both NAD+ and FAD+ as electron carriers.
D. It uses both NAD+ and FAD+ as electron carriers.
Which event explains why FADH₂ produces less ATP than NADH?
A. FADH₂ skips proton pumping entirely
B. FADH₂ enters the ETC at complex II
C. FADH₂ carries lesser number of electrons
D. FADH₂ does not release electrons
B. FADH₂ enters the ETC at complex II
Which pathways will result in carbon dioxide and NADH being released but not ATP?
pyruvate oxidation
Which event directly generates ATP by substrate-level phosphorylation?
A. oxidizing G3P and transferring its electron to NAD+
B. transferring a phosphate group from ATP to fructose-6- phosphate
C. transferring of a phosphate group from PEP to ADP
D. rearranging 3-phosphoglycerate to 2-phosphoglycerate by an enzymatic shift of the position of a phosphate group
C. transferring of a phosphate group from PEP to ADP
Which of the following activities DOES NOT occur during pyruvate oxidation?
A. The carboxyl group of pyruvates is removed as carbon dioxide.
B. The pyruvate transfers its phosphate group to ADP to yield ATP.
C. The oxidized 2-carbon fragment becomes attached to coenzyme A.
D. The 2-carbon fragment becomes oxidized, and the electrons are transferred to NAD+.
B. The pyruvate transfers its phosphate group to ADP to yield ATP.
How many molecules of CO2 would be produced by 3 glucose molecules after aerobic cellular respiration?
12
What is the immediate source of energy used to convert ADP + Pi to ATP?
A. the energy released from substrate-level phosphorylation
B. the energy released from the oxidation of NADH and FADH2
C. the energy released as electrons flow through the electron transport system
D. the energy released from ATP synthase pumping H+ down their concentration gradient
D. the energy released from ATP synthase pumping H+ down their concentration gradient
Which pathway results in the production of the most ATP molecules during aerobic cellular respiration of one glucose molecule?
oxidative phosphorylation
A cell is found to have very low ATP levels, causing the early steps of glycolysis to slow down. Which step is most directly affected?
A. The conversion of pyruvate into acetyl-CoA
B. The phosphorylation of glucose using ATP
C. The splitting of fructose-1,6-bisphosphate
D. The oxidation of G3P and reduction of NADH
B. The phosphorylation of glucose using ATP
Which of the following is NOT an event that occurs during pyruvate oxidation?
A. Pyruvate (3C) is decarboxylated, releasing one molecule of CO₂.
B. Electrons are transferred to NAD⁺, forming NADH.
C. Acetyl-CoA combines with oxaloacetate to form citrate.
D. The 2-carbon acetyl group binds to coenzyme A.
C. Acetyl-CoA combines with oxaloacetate to form citrate.
How many molecules of NADH would be produced by five turns of the citric acid cycle?
15
What is the immediate result of protons being pumped into the intermembrane space?
A. formation of pyruvate from phosphoenolpyruvate
B. creation of proton gradient that drives ATP synthesis
C. release of carbon dioxide as a byproduct of decarboxylation
D. increase in NADH production from NAD⁺ as electrons are transferred along ETC
B. creation of proton gradient that drives ATP synthesis
Which stage/s of cellular respiration releases carbon dioxide?
Stage I: glycolysis
Stage II: pyruvate oxidation
Stage III: Krebs cycle
Stage IV: oxidative phosphorylation
A. stage III only
B. stages III and IV
C. stages II and III
D. stages II, III, and IV
C. stages II and III
Which of the following is NOT a step in the energy-payoff phase of glycolysis?
A. 2-phosphoglycerate is converted to phosphoenolpyruvate (PEP).
B. Phosphoenolpyruvate (PEP) donates a phosphate group to ADP to form ATP.
C. Glyceraldehyde-3-phosphate (G3P) is oxidized, and NAD⁺ is reduced to NADH, forming 1,3-bisphosphoglycerate.
D. Fructose-6-phosphate is phosphorylated to fructose-1,6-bisphosphate.
D. Fructose-6-phosphate is phosphorylated to fructose-1,6-bisphosphate.
During an experiment, a mutation alters the pyruvate oxidation pathway so that FAD accepts electrons from pyruvate instead of NAD⁺. What is the most direct consequence of this change?
A. Pyruvate cannot be converted into acetyl-CoA.
B. NADH levels increase to maintain ATP production.
C. ATP production decreases due to fewer protons pumped.
D. The pyruvate is converted into lactate via fermentation.
C. ATP production decreases due to fewer protons pumped.
Which event produces NADH in the Krebs cycle?
A. Conversion of citrate into its isomer isocitrate
B. Oxidation of isocitrate (6C) and α-ketoglutarate (5C)
C. Oxidation of succinate (4C) to fumarate (4C)
D. Production of ATP with Pi coming from succinyl CoA (4C-CoA)
B. Oxidation of isocitrate (6C) and α-ketoglutarate (5C)
If 5 molecules of Acetyl CoA enter Krebs Cycle, how many molecules of ATP are produced after oxidative phosphorylation?
45 ATPs