Question

Write the equation for the process of breakdown of glucose in a cell : (a) in presence of oxygen (b) in the absence of oxygen

Answer 1

in presence of oxygen equation is C6H12O6+6O2=6CO2+12H2O and in absence of oxygen equation is C6H12O6=lactic acid + ethanol 
aerobic respiration occurs in green plants and anaerobic respiration occurs in yeast etc

Answer 2

Answer:

(i) In presence of oxygen, aerobic respiration takes place in which the glucose is converted into Carbon dioxide & water and energy.

The reaction is as follows -

C6H12O6 + O2 -----> CO2 + H2O + Energy

(ii) In the absence of oxygen, the glucose undergoes alcoholic fermentation and lactic acid fermentation. During alcoholic fermentation process, the glucose is converted into Carbon Dioxide and  Ethanol and its releases some amount of energy. The reaction of this process is as follows -  

Glucose - C6H12O6

Ethanol - C2H5OH

Carbon Dioxide - CO2

C6H12O6 -----> C2H5OH + CO2 + Energy

During lactic acid fermentation, glucose get's transformed into lactic acid.

C6H12O6 ------> CH3CHOHCOOH (Lactic Acid)