Energy flow and chemical recycling in ecosystems Metabolic pathways involved in harvesting the energy of glucose Glycolysis and cellular respiration Glycolysis and fermentation Concept 9.1 How do metabolic pathways yield energy? Redo reactions: chemical reactions that transfer electrons Oxidation: substance loses electrons Reduction: substance gains electrons Oxidation of organic molecules during cellular respiration Nicotinamide Adenine Dinucleotide- electron carrier/acceptor NADH passes electrons to the electron transport chain when O2 is present Cellular respiration occurs in the mitochondria Stages of cellular respiration Glycolysis occurs in cytoplasm Breaks down glucose with end product being pyruvic End process pyruvic goes to citric acid cycle