Do plants breathe? How a cell turns food into ATP, and how glucose is split into pyruvic acid in glycolysis. What a cell does with pyruvic acid when there is no oxygen: alcoholic and lactic acid fermentation.
3 lessons, about 1 h 20 min3 simulations10 problems3 practice questionsPython in every lesson
Created by StemPy LabPlants have no lungs. Each part exchanges gases by diffusion through stomata, lenticels and the root surface. Inside the cells, respiration breaks down food, mostly glucose, in small steps and keeps the energy in ATP. This lesson ends with the three stages: glycolysis, then fermentation without oxygen, or aerobic respiration in the mitochondria.
Glycolysis splits one glucose molecule into two molecules of pyruvic acid in ten reactions in the cytoplasm. Two ATP are spent at the start and four are made later by substrate level phosphorylation, so the net gain is 2 ATP. Two molecules of NADH are formed where PGAL is oxidised.
With no oxygen, a cell lets pyruvic acid take hydrogen from NADH, so that NAD+ is made again. Yeast changes pyruvic acid into ethanol and carbon dioxide. Some bacteria and muscle cells change it into lactic acid. Fermentation releases less than 7 per cent of the energy of glucose, and the net gain is only 2 ATP.
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