Glycolysis
In aerobic glycolysis, the two molecules of NADH made in the cytosol are reoxidized to NAD⁺ by transfer of their electrons to the ETC in the mitochondria.
What our notes say
- In aerobic glycolysis, the two molecules of NADH made in the cytosol are reoxidized to NAD⁺ by transfer of their electrons to the ETC in the mitochondria. (Biochemistry Mid-Semester Exam — 2016 (Past Paper))
- In anaerobic glycolysis, the two NADH are reused by the LDH to generate $2\text{NAD}^+$ that are reused by the G3P-DH to keep glycolysis going. (Biochemistry Mid-Semester Exam — 2016 (Past Paper))
- The sixth step of glycolysis involves the participation of: (bchem EOY 2011 — Past Paper Questions & Answers)
- The pathway of gluconeogenesis shares seven steps with the pathway of glycolysis (bchem EOY 2011 — Past Paper Questions & Answers)
- (b) Hypoperfusion causes tissue hypoxia, so cells switch to anaerobic glycolysis. (Chemical Pathology Semester 1 — Short Answer Questions)
- b) With relevant reaction(s), distinguish between aerobic and anaerobic glycolysis. (Biochemistry End of Year Exam — 2014 (Past Paper))
Study material on Glycolysis
- Biochemistry Mid-Semester Exam — 2016 (Past Paper)
- CLINICAL BIOCHEMISTRY LAQs & SAQs
- Blood Biochemistry
- Endocrine and Metabolic Pathology MCQs for Medical Students
- ONCOPATHOLOGY - 30 KEY SHORT ANSWER QUESTIONS Hallmarks 1,2 & 3
- Medical Biochemistry, Genetics, and Molecular Biology
- Integrated Tissue Metabolism -LAQs and SAQs
- Hallmarks of Cancer: Molecular Basis, Cell Cycle & Oncogenes
- Medical Biochemistry II (MBMB 2200) -2
- bchem EOY 2011
- Biochemistry Mid-Semester 2 CAT — 2013 (Past Paper)
- ONCOPATHOLOGY MCQs - HALLMARKS OF CANCER
- Oncopathology Hallmarks of Cancer MCQs
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Practice questions on Glycolysis
Which of the following substances is LEAST likely to inhibit glycolysis?
- Maleinimide
- Monoiodine acetate
- Sodium fluoride
- Cresol
Answer: A. Maleinimide is a reagent that reacts with sulfhydryl groups. While it can affect enzymes, it's not a classic inhibitor of glycolysis. Monoiodine acetate and sodium fluoride are well-known inhibitors of specific glycolytic enzymes (iodoacetate inhibits glyceraldehyde-3-phosphate dehydrogenase, and fluoride inhibits enolase). Cresol can also have inhibitory effects on cellular processes.
Which of the following substances is an inhibitor of glycolysis?
- Maleimide
- Monoiodoacetate
- Sodium fluoride
- Cresol
Answer: B. Monoiodoacetate is a potent inhibitor of glycolysis. It inhibits the enzyme glyceraldehyde-3-phosphate dehydrogenase by alkylating a critical cysteine residue in the active site. Maleimide is also an alkylating agent and can inhibit enzymes, but monoiodoacetate is a classic glycolytic inhibitor. Sodium fluoride can inhibit enolase in vitro. Cresol is a general cellular toxin.
Which cause of hypoxia differs from ischemia in that it allows anaerobic glycolysis to continue?
- Carbon monoxide poisoning
- Coronary artery occlusion
- Venous thrombosis
- Arterial atherosclerotic narrowing
- , blood flow is reduced, compromising delivery of substrates for glycolysis, making ischemia more injurious than hypoxia alone.
Answer: A. Carbon monoxide poisoning causes hypoxia by reducing oxygen-carrying capacity of blood, but blood flow continues, allowing delivery of glucose for anaerobic glycolysis. In ischemia (b, c, d), blood flow is reduced, compromising delivery of substrates for glycolysis, making ischemia more injurious than hypoxia alone. ---
Rapidly growing tumors like Burkitt lymphoma utilize aerobic glycolysis despite its inefficiency. What clinical application exploits this metabolic characteristic?
- Measuring serum lactate levels
- PET scanning with 18F-fluorodeoxyglucose
- Detecting mitochondrial enzyme levels
- Measuring oxygen consumption rates
Answer: B. ** The "glucose hunger" of tumors using aerobic glycolysis is exploited clinically through PET scanning, where patients receive 18F-fluorodeoxyglucose (a non-metabolizable glucose derivative). Rapidly growing tumors show marked PET-positivity due to high glucose uptake. ---
Which oncogenes and tumor suppressors are now recognized to stimulate glucose uptake and favor aerobic glycolysis?
- E-cadherin, VHL, and TSP-1
- TP53, PTEN, and Akt
- MMP-9, HGF, and VEGF
- RAG1, RAG2, and AID
Answer: B. ** TP53, PTEN, and Akt (an intermediary in RAS signaling) stimulate glucose uptake by affecting glucose transporter proteins and favor aerobic glycolysis. This demonstrates that the Warburg effect becomes "hard-wired" through mutations in key regulatory genes. ---
In the Warburg effect, how many ATP molecules are produced per glucose molecule through aerobic glycolysis?
- 2
- 4
- 18
- 36
Answer: A. ** Aerobic glycolysis produces only 2 ATP molecules per glucose molecule, compared to 36 ATP from mitochondrial oxidative phosphorylation, yet supports rapid tumor growth. ---