3. _____ Gasoline-powered internal combustion engines (like the one in most cars

Question

3. _____ Gasoline-powered internal combustion engines (like the one in most cars) convert the chemical energy in gasoline into usable thermal energy by controlling the rate of combustion of gas in the cylinders of the engine. That same chemical energy could be released by tossing a match in the gas tank. Thinking about the similarities between cars and cells, why don’t cells just use one single reaction to release all of the energy stored in glucose at once rather than using that complicated series of steps associated with cellular respiration?

A) A single reaction would not be possible, as it would violate the second law of thermodynamics.

B) A single reaction would produce very little energy in comparison to smaller, controlled reactions.

C) A single reaction that converted glucose to the same products as cellular respiration would likely Be endergonic, requiring the input of substantial amounts of energy.

D) A single reaction could not use O2 and cellular respiration is not possible in anaerobic conditions.

E) A single reaction would cause more of the energy to be lost as heat and that energy would not be Available to do cellular work.

Explanation / Answer

Thinking about the similarities between cars and cells: A single reaction that converted glucose to the same products as cellular respiration would likely be endergonic, requiring the input of substantial amounts of energy. This is because along with the substrate all the intermediates to be converted at a time into products and thus require more energy input than the energy output.

Since, the cellular respiration is carried out in a series of events, the energy released will be in high amounts (32 ATP per glucose molecule), then ATP is to be released in a single step require various inputs and reducing power are to be generated at a time for all intermediate reactions which require more input energy. Hence, option C is correct.

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