Question

Describe what happens under anaerobic conditions in muscle cells and in yeast.

a) Glycolysis produces lactate in muscle cells and alcohol in yeast.
b) Cellular respiration occurs in both muscle cells and yeast.
c) Oxygen is consumed in muscle cells, leading to lactic acid production, while yeast undergoes alcoholic fermentation.
d) Both muscle cells and yeast rely on the Krebs cycle under anaerobic conditions.

Answer 1

Under anaerobic conditions, muscle cells convert pyruvate into lactic acid, while yeast cells perform alcoholic fermentation, producing ethanol and carbon dioxide. Both processes allow for the continuation of ATP production through glycolysis in the absence of oxygen.

Step-by-step explanation:

Under anaerobic conditions, muscle cells and yeast cells rely on glycolysis to produce ATP, as the citric acid cycle and oxidative phosphorylation (parts of aerobic respiration) cannot occur without oxygen. In muscle cells, pyruvate from glycolysis is converted into lactic acid, while yeast cells perform alcoholic fermentation, converting pyruvate into ethanol and carbon dioxide.

For muscle cells, this anaerobic pathway leads to the production of lactic acid and allows the continuation of glycolysis by regenerating NAD+ from NADH. This is a temporary solution for energy production during intense activity when oxygen supply is low.

In contrast, yeast cells, during fermentation, produce ethanol and carbon dioxide from pyruvate. This process is exploited in the making of alcoholic beverages and bread. In both muscle cells and yeast, anaerobic conditions inhibit the Krebs cycle and subsequent oxidative phosphorylation, limiting ATP production to what can be generated through glycolysis alone.