Question

When a yeast cell respires, ATP formed is
A. 4
B. 2
C. 6
D. 8

Answer 1

Hint: Cellular respiration includes mainly two pathways: aerobic and anaerobic respiration. Yeast cells produce ethanol and carbon dioxide in anaerobic conditions. Very less amount of energy is produced by this process.

Complete answer: Kingdom Fungi includes the members of the yeast. They are classified under the phyla Ascomycota (sac fungi) and Basidiomycota (higher fungi). They are single celled multicellular organisms. They are found in a wide variety of habitats. The most common habitats of yeast are plant leaves, flowers, and fruits as well as soil. They are also found on the surface of the skin and in the intestinal tracts of warm blooded animals. They can live symbiotically or as parasites.
Cellular respiration is used by the yeast cell to respire. It can be done in the absence of oxygen. It is called anaerobic respiration. In this process glucose is converted to ATP and carbon dioxide. The energy produced by anaerobic respiration is 5 percent of the energy stored in glucose. By this process glucose is converted into ethanol and carbon dioxide. Only 2 molecules of ATP are produced by this. It is because of the absence of the oxygen and partial breakdown of glucose occur. It is also called alcoholic fermentation.

Hence, the correct answer is option (B).

Note: Yeast produces the gas due to which bread puffs up. It is used in bakery products. Production of carbon dioxide the yeast on bread rises. Cellular respiration in aerobic condition produces CO2 and H2O. In aerobic respiration, the energy production is more. In case of anaerobic condition, muscle cells produce lactic acid. Due to this, people feel tired.