BiochemistryLesson 1 of 3 in the course Microbial Metabolism

Carbohydrate Catabolism: Glycolysis, Pyruvate Oxidation, and the Krebs Cycle

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Carbohydrate catabolism breaks down sugars to capture energy and supply molecules used to build cell components. This lesson focuses on glycolysis, its energy yield, and alternative pathways microbes can use to process glucose.

Chemoheterotrophs obtain energy and carbon from organic compounds. Their carbohydrate catabolism may begin with polysaccharides such as glycogen, starch, or cellulose. Enzymes hydrolyze the glycosidic bonds linking their glucose monomers: amylases act on starch and glycogen, while cellulases act on cellulose. The released glucose can then enter pathways that capture energy and provide metabolic intermediates.

All flashcards

What is the net yield of EMP glycolysis per glucose?
Two ATP, two NADH, and two pyruvate molecules.
What is substrate-level phosphorylation?
Direct transfer of a phosphate group from an organic intermediate to ADP to form ATP.
What does the transition reaction do to pyruvate?
It releases CO₂, produces NADH, and attaches the remaining two-carbon acetyl group to coenzyme A.
What is the Krebs cycle's yield per turn?
Two CO₂, three NADH, one FADH₂, and one ATP or GTP.
What does it mean that the Krebs cycle is amphibolic?
It contributes to both catabolism and anabolism.

Quiz questions

  1. Where does the Krebs cycle occur in eukaryotic and prokaryotic cells, respectively?Answer: Mitochondrial matrix in eukaryotes; cytoplasm in prokaryotes.
  2. What happens during the transition reaction as pyruvate becomes acetyl-CoA?Answer: CO₂ is released, NADH is produced, and the acetyl group joins CoA.
  3. What is produced in one turn of the Krebs cycle per acetyl group?Answer: Two CO₂, three NADH, one FADH₂, and one ATP or GTP.
  4. What does the term amphibolic mean when applied to a metabolic pathway?Answer: The pathway functions in both molecule breakdown and molecule synthesis.
  5. What happens to the four-carbon molecule that accepts an acetyl group at the start of each Krebs cycle turn?Answer: It is regenerated by the cycle's final reactions.

Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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