Question 14 **Question: Which one is not a truth about fermentation?**- Fermentation is a metabolic pathway in living cells.- Fermentation occurs when oxygen is present.- Carbon dioxide and ethanol are the final products of fermentation.- Muscle cells undergo fermentation when they work hard and have exhausted their oxygen.**Explanation:**This question asks which statement about fermentation is incorrect. The statements cover various aspects of fermentation as a biological process.- Fermentation indeed is a metabolic process occurring in living cells.- Fermentation typically happens in the absence of oxygen.- In certain types of fermentation, such as alcoholic fermentation, carbon dioxide and ethanol are indeed the final products.- Muscle cells can undergo lactic acid fermentation when they are low on oxygen during intense exercise. Therefore, the statement "Fermentation occurs when oxygen is present" is not true. Fermentation usually takes place in anaerobic (oxygen-free) conditions.

Fermentation is a process in which incomplete oxidation of glucose takes place. It can be achieved only by certain enzymes such as pyruvic acid decarboxylase and alcohol dehydrogenase. This process leads to generation of ATP, energy currency of the cell. Bacteria converts sugar into lactic acid by this process. Fermentation is a metabolic process which takes place in living organisms under anaerobic conditions ( absence of oxygen). Many bacterial cells and yeast undergoes fermentation. Yeast ferments the sugar substrate and produce carbon dioxide and ethanol. This property of yeast is exploited in the production of alcohol beverages and bakery items. Therefore, the answer is Fermentation occurs when oxygen is present. Other options are incorrect as all the other statements are absolutely correct about fermentation. Option a is incorrect as fermentation is a metabolic process which takes place in living organisms such as yeast. Option c is incorrect as fermentation leads to the production of carbon dioxide gas and ethanol. Option d is incorrect as muscle cells undergo fermentation when vigorous excercise is performed and there is exhaustion of oxygen in cells. Therefore the statement " Fermentation occurs when oxygen" is present is not true .