Video Transcript
Which of the following best compares the energy transfers of ATP and glucose in the
cell? (A) The breakdown of a glucose molecule transfers less energy than the breakdown of
an ATP molecule, but it transfers it faster. (B) The breakdown of an ATP molecule transfers less energy than the breakdown of a
glucose molecule, but it transfers it faster. (C) The breakdown of glucose and of ATP molecules transfer equal amounts of
energy.
This question is asking us to compare energy transfers between ATP and glucose. We get glucose from the food we eat, mostly in the form of carbohydrates. This food is broken down to release the sugar molecule glucose. During a process called cellular respiration, this glucose is metabolized by our
cells and converted into carbon dioxide and water. By doing this, energy is extracted from the chemical bonds in glucose and stored in
molecules of ATP.
ATP, or adenosine triphosphate, stores this energy in the form of high-energy
phosphate bonds. The three phosphate groups are linked to one another by high-energy bonds that can be
broken to release energy. It is within these bonds that energy from glucose is stored.
When energy is needed, the covalent bond between the second and third phosphate
groups of ATP, as indicated by the green arrow, is broken and released for numerous
biological processes in the cell. The breakdown of one glucose molecule is enough to make around 38 molecules of
ATP. So, clearly, glucose has a lot more stored energy than ATP does.
However, cellular respiration is a multistep process that takes time and numerous
enzymes. So the transfer of energy from glucose is slower compared to the transfer of energy
from ATP. Therefore, the option that best compares energy transfers between ATP and glucose is
given by answer choice (B). The breakdown of an ATP molecule transfers less energy than the breakdown of a
glucose molecule, but it transfers it faster.
