Study guides › B/B › Biochemistry
Glycolysis, Fermentation & Gluconeogenesis
Glucose is the central fuel of the body. You will follow it through the ten steps of glycolysis, see how cells regenerate NAD⁺ by fermentation, build glucose back by gluconeogenesis, and learn how the pentose phosphate pathway and glycogen are controlled by hormones.
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What this chapter covers
- Glycolysis: The Ten Steps. Expect questions on which enzyme does what, where ATP and NADH appear, and which steps are irreversible.
- Regulating Glycolysis & Counting ATP. Hormones and energy signals meet at PFK-1 and pyruvate kinase, and every exam wants the 2.5 and 1.5 ATP totals.
- Fermentation, Pyruvate Fates & Other Sugars. Without oxygen, cells must regenerate NAD⁺ or glycolysis stops. Know both fermentations and how fructose and galactose join in.
- Gluconeogenesis. Gluconeogenesis is glycolysis run backward with three bypasses; know the enzymes, the location of each, and the cost.
- Pentose Phosphate Pathway & Glycogen Metabolism. The PPP makes NADPH and ribose; glycogen stores glucose. Both are tested through enzyme deficiencies and hormone effects.
Key points to know
- Glucose → 2 pyruvate; net 2 ATP and 2 NADH
- Investment: hexokinase and PFK-1 each use 1 ATP
- Regulated steps: hexokinase, PFK-1, pyruvate kinase
- PFK-1: ATP and citrate inhibit; AMP and F2,6BP activate
- Fermentation regenerates NAD⁺; ATP still comes only from glycolysis (2 per glucose)
- Animals: pyruvate → lactate (LDH); yeast: pyruvate → acetaldehyde → ethanol + CO₂
- Three bypasses: PC + PEPCK, FBPase-1, glucose-6-phosphatase
- Occurs mainly in liver (and kidney); G6Pase is in the ER
Try a practice question
Which glycolytic enzyme reduces NAD⁺ to NADH?
- Hexokinase
- Glyceraldehyde-3-phosphate dehydrogenase
- Enolase
- Pyruvate kinase
Show the answer
B. GAPDH oxidizes the aldehyde of G3P while adding Pi, and the electrons go to NAD⁺. The other three enzymes do not carry out redox chemistry.
Common questions
What does this chapter cover?
Glycolysis, Fermentation & Gluconeogenesis covers Glycolysis: The Ten Steps, Regulating Glycolysis & Counting ATP, Fermentation, Pyruvate Fates & Other Sugars, Gluconeogenesis, Pentose Phosphate Pathway & Glycogen Metabolism.
What should I know first?
Glucose → 2 pyruvate; net 2 ATP and 2 NADH Investment: hexokinase and PFK-1 each use 1 ATP Regulated steps: hexokinase, PFK-1, pyruvate kinase
24 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.