VCE · Biology · Biochemical Pathwayslive from the app
Aerobic vs Anaerobic Respiration
Oxygen never touches glycolysis; it only decides what happens to pyruvate afterwards. With oxygen, pyruvate and NADH go into the mitochondrion and the electron transport chain lifts the yield to roughly 30 ATP per glucose. Without it, the chain stalls and the cell ferments in the cytosol: no extra ATP, just a way to turn NADH back into the NAD⁺ that glycolysis needs. Animal cells end with lactic acid; yeast ends with ethanol and CO₂, but both keep only the 2 ATP from glycolysis.
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the one idea
why this one carries the topic.
Life runs on two reactions pointing opposite ways: one traps energy from light, one lets it out of sugar. Everything else here is detail on those two.
Glucose runs down a glycolysis channel in the cytosol to a pyruvate fork: with oxygen the flow sweeps right into a drawn mitochondrion (ETC, ~30 ATP); without it the flow sweeps left into fermentation, which returns NAD⁺ to glycolysis and ends in lactic acid in an animal cell or ethanol and CO₂ in yeast.
what examiners catch — Students write that fermentation makes extra ATP, or swap the products: lactic acid in animals, ethanol and CO₂ in yeast, both in the cytosol. The mark comes from naming the location, naming pyruvate and NADH as the inputs, and stating that NAD⁺ is regenerated so glycolysis can continue.
what you leave with
five things, not forty.
Glycolysis runs in the cytosol with or without oxygen, splitting glucose into two pyruvate and netting 2 ATP and 2 NADH.
With oxygen, pyruvate and NADH enter the mitochondrion, where the electron transport chain uses O₂ as the final electron acceptor and the total yield reaches about 30 to 32 ATP per glucose.
Without oxygen, fermentation in the cytosol takes pyruvate and NADH as inputs and makes no extra ATP; the cell keeps only the 2 ATP from glycolysis.
Fermentation exists to regenerate NAD⁺, because glycolysis stalls the moment it runs out of NAD⁺.
In animals the fermentation output is lactic acid; in yeast it is ethanol plus CO₂, so the ATP count is identical but the product differs.
what's underneath
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this conceptaerobic vs anaerobic respirationGlucose runs down a glycolysis channel in the cytosol to a pyruvate fork: with oxygen the flow sweeps right into a drawn mitochondrion (ETC, ~30 ATP); without it the flow sweeps left into fermentation, which returns NAD⁺ to glycolysis and ends in lactic acid in an animal cell or ethanol and CO₂ in yeast.
sits under itcellular respiration: the big picturebecause anaerobic is the big picture with the ending changed
sits under itglycolysis structure and controlbecause The fork starts with pyruvate and NADH, the outputs of glycolysis
sits under itthe three stages of cellular respirationbecause Places fermentation against the aerobic stages it replaces
sits under itoxidative phosphorylation and the electron transport chainbecause Explains why no oxygen means the chain stalls and NADH piles up
the rest of biochemical pathways
11 more, same treatment.
Each one is its own knowscape in the app — built for how a particular student takes things in, not one explanation handed to everybody.
c3, c4 and cam plantsin the appfactors affecting the rate of photosynthesisin the appregulation by feedback inhibitionin the applight-dependent and light-independent stagesin the appoxidative phosphorylation and the electron transport chainin the appthe krebs cyclein the appthe three stages of cellular respirationin the appenzymes and the regulation of pathwaysin the appphotosynthesis: inputs, outputs and locationin the appglycolysis structure and controlin the appcellular respiration: the big picturein the app
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