Question

n a reproduction of an experiment famously performed by Louis Pasteur, you cultured yeast in the absence of oxygen (anaerobic growth) and measured (1) the rate of cell division, (2) the rate of glucose consumption, and (3) the intracellular ATP:ADP ratio. You then moved the cells to an incubator containing normal atmosphere (i.e., 21% oxygen), completed a second set of measurements, and made the following observations:

• The rate of cell division increased considerably after the addition of oxygen (aerobic growth)
• Glucose consumption dropped dramatically after the addition of oxygen
• Intracellular ATP:ADP ratios increased significantly (from 2:1 in the absence of oxygen to 10:1 in the presence of oxygen)

Explain how the mitochondria in the yeast contribute to the dramatic drop in glucose utilization and increase in ATP concentrations in the presence of oxygen.

Answer 1

In Yeast two to types of respiration takes place

1. aerobic respiration
2. anaerobic respiration

Aerobic respiration

Aerobic respiration takes place when oxygen molecule is present.

During aerobic respiration  the yeast cell utilises the sugar molecule present and releases carbon di oxide, water and high energy.

Yeast cell + glucose=carbon di oxide +water+32 ATP

Thus mitochondria in yeast utilises all the available glucose present leading to the production of ATP by means of glycolysis, oxidative phosphorylation and kerbs cycle.

Anaerobic respiration

During anaerobic respiration the energy production is low and the yeast utilises the glucose to produce carbon di oxide and alcohol.

yeast cell +glucose= carbon di oxide+alcohol+2 ATP