What compound can be made from glucose and serves as long-term energy storage?
A. CO2 B. H2O C. ATP D. Mitochondria
The Correct Answer and Explanation is:
The correct answer is C. ATP.
While glucose is the body’s primary source of quick energy, long-term energy storage is facilitated by converting glucose into glycogen and fats, both of which are metabolized when energy is needed. However, ATP, or adenosine triphosphate, serves as the immediate energy currency of the cell and is synthesized during the breakdown of glucose.
Explanation:
Glucose, a simple sugar, is metabolized through cellular respiration, a multi-step process occurring in the cytoplasm and mitochondria. The primary purpose of this process is to generate ATP. Cellular respiration involves three key stages:
- Glycolysis (in the cytoplasm): Glucose is broken down into two molecules of pyruvate, generating a small amount of ATP and NADH.
- Krebs Cycle (in the mitochondrial matrix): Pyruvate is further processed to produce electron carriers like NADH and FADH2.
- Electron Transport Chain (ETC) (in the inner mitochondrial membrane): NADH and FADH2 donate electrons, which power ATP synthase to generate large amounts of ATP.
While ATP is essential for immediate energy needs, it is not used for long-term energy storage because it is unstable and consumed quickly by cells. Excess glucose, not immediately needed for ATP production, is stored in the form of glycogen (in the liver and muscles) or converted into fat for long-term storage in adipose tissue. During fasting or intense exercise, glycogen and fat can be broken down to generate glucose or ATP as required.
The other options are incorrect:
- A. CO₂ is a byproduct of glucose metabolism, not an energy-storage compound.
- B. H₂O is also a byproduct in the electron transport chain.
- D. Mitochondria are organelles, not compounds.
In summary, ATP directly links glucose metabolism to energy use, but glycogen and fats are better examples of long-term energy storage.