Answer: A. Pyruvic acid, the product of glycolysis, is the starting block for both the Krebs cycle and fermentation.
Explanation: Glycolysis is a metabolic pathway that oxidize glucose producing pyruvic acid and few ATP molecules. If the cellular microenvironment is aerobic, pyruvic acid is converted in Acetyl coA and enters into Krebs cycle and later into electron transport chain, which produce large amounts of ATP. If the cellular microenvironment is anaerobic, fermentation occurs and pyruvic acid is converted in lactic acid, ethanol, etc, producing only few ATP.
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For gases
Answer:
Prokaryotes or unicellular organisms, without a nucleus, are categorized in two different kingdoms: Eubacteria and Archaebacteria or simply, bacteria and archaea, respectively. Sometimes these two kingdoms are also clubbed together as Monera. Unicellular organisms with a nucleus are part of the kingdom Protista.