Question

When 10,000 molecules of ATP are hydrolyzed to ADP and Pi in a test tube, about twice as much heat is liberated as when a cell hydrolyzes the same amount of ATP. Which of the following is the best explanation for this observation?

A. The reaction in cells must be catalyzed by enzymes, but the reaction in a test tube does not need enzymes.B. Cells are open systems, but a test tube is a closed system.C. Reactant and product concentrations in the test tube are different from those in the cell.D. Cells are less efficient at heat production than nonliving systems.E. The hydrolysis of ATP in a cell produces different chemical products than does the reaction in a test tube.

Answer 1

The best explanation for the observation that twice as much heat is released when ATP is hydrolyzed in a test tube compared to in a cell is that cells use energy coupling to utilize the energy for work, reducing the amount of energy lost as heat.

Step-by-step explanation:

When 10,000 molecules of ATP are hydrolyzed to ADP and Pi in a test tube, about twice as much heat is liberated as when a cell hydrolyzes the same amount of ATP. The best explanation for this observation is that cells use a process called energy coupling to harness the energy released by ATP hydrolysis to perform work inside the cell. This is in contrast to a test tube reaction, where the free energy released is simply lost as heat without doing cellular work. In cellular environments, exergonic reactions such as ATP hydrolysis drive endergonic reactions, which reduce the amount of free energy released as heat. One specific example of energy coupling in cells is the Na+/K* pump, which uses the phosphorylation process to transport sodium and potassium ions.

In summary, option C is correct: Reactant and product concentrations in the test tube are different from those in the cell. The cellular environment is designed to efficiently use the energy from ATP hydrolysis, whereas in a test tube, the reaction simply releases heat without doing work.

Answer 2

Answer: (C) Reactant and product concentrations in the test tube are different from those in the cell.

Explanation:.

More heat energy is liberated because the test tube is an enclosed system where the energy liberated from hydrolysis of ATPs is converted to majorly heat energy . However, in a living cell parts of the energy from ATPs hydrolysis is converted to other forms of energy to do biological work in the body, while the rest (60 %) is liberated as heat energy. Therefore less heat is liberated in the body compare to test tube where majority is liberated as heat; since there is no biological work to use the energy for.