Question

in muscle cells, fermentation produces

pyruvate
lactate, nadh, and atp
carbon dioxide, ethanol, and nad+
carbon dioxide, ethanol, nadh, and atp
lactate and nad+

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part b

in fermentation

pyruvate... nadh
lactate... nadh
nad+... pyruvate
nadh... lactate
lactate... ethanol

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Explanation:

For the first question:
In muscle cells, during fermentation (lactic acid fermentation), pyruvate is the starting molecule. The goal is to regenerate \(NAD^{+}\) which is crucial for glycolysis to continue. Pyruvate is reduced to lactate, and \(NADH\) is oxidized to \(NAD^{+}\). ATP is not produced during the fermentation step itself (ATP is produced in glycolysis). Pyruvate is the reactant, not the product of muscle - cell fermentation. The options with ethanol are for alcoholic fermentation (not muscle - cell fermentation).

For the second question:
In fermentation (e.g., lactic acid fermentation in muscle cells), pyruvate acts as the oxidizing agent (it gets reduced). \(NADH\) acts as the reducing agent (it gets oxidized). The general concept in fermentation is that an organic molecule (like pyruvate) is reduced, and \(NADH\) (which was produced in glycolysis) is oxidized to \(NAD^{+}\)

Answer:

First question: lactate and \(NAD^{+}\)
Second question: pyruvate... \(NADH\)