Glycolysis Is an Energy-Conversion Pathway in Many organisms
The Glycolytic Pathway Is Tightly Controlled
Glucose Can Be Synthesized from Non-carbohydrate Precursors
Gluconeogenesis and Glycolysis Are Reciprocally Regulated
the sequence of reactions that metabolizes one molecule of glucose to two molecules of pyruvate with the concomitant net production of two molecules of ATP.
Glycolysis is an ancient pathway employed by a host of organisms.
This process is anaerobic (i.e., it does not require O2), in as much as it evolved before the accumulation of substantial amounts of oxygen in the atmosphere.
Pyruvate can be further processed anaerobically to lactate or ethanol.
Under aerobic conditions(need O2), pyruvate can be completely oxidized to CO2, generating much more ATP.
Position of glycolysis: cytoplasm
Glucose generated from dietary Carbohydrates
Stage 1: conversion of glucose into fructose 1,6-bisphosphate, and cleavage into two three-carbon fragments;
stage 2: ATP is generated when the three carbon fragments are oxidized to pyruvate.
Diverse fates of pyruvate
Significance of glycolysis
Fermentations provide usable energy in the absence of oxygen
- obligate anaerobes: Clostridium tetani (破傷風杆菌), Clostridium botulinum (肉毒杆菌)
- intense exercise
- food industry: sour cream, yogurt, various cheeses, beer, wine, and sauerkraut
Maintaining redox balance
The NADH produced by the glyceraldehyde 3-phosphate dehydrogenase reaction must be reoxidized to NAD+ for the glycolytic pathway to continue. In alcoholic fermentation, alcohol dehydrogenase oxidizes NADH and generates ethanol. In lactic acid fermentation (not shown), lactate dehydrogenase oxidizes NADH while generating lactic acid.
Glycolysis of other hexoses