During cellular respiration, glucose (C_6H_{12}O_6) is broken down in the presence of oxygen (O_2) to produce carbon dioxide (CO_2), water (H_2O), and ATP (adenosine triphosphate). The primary purpose of this process is to convert the energy stored in the chemical bonds of glucose into a form that the cell can use for its various functions, which is ATP.
Here is a detailed step-by-step explanation of what happens to the energy in the bonds of glucose during cellular respiration:
1. Breaking Down Glucose:
In the first stage of cellular respiration, glucose is broken down in a series of enzymatic reactions. This process begins with glycolysis, which takes place in the cytoplasm of the cell. During glycolysis, glucose is broken down into two molecules of pyruvate, releasing a small amount of energy that is captured in the form of ATP and NADH.
2. Pyruvate Oxidation & Citric Acid Cycle:
The pyruvate molecules are then transported into the mitochondria, where they are further oxidized in the citric acid cycle (also known as the Krebs cycle). Here, the carbon atoms from glucose are progressively oxidized, and the energy released from these reactions is captured in the form of NADH and FADH_2, which are energy carrier molecules. In the process, carbon dioxide is released as a byproduct.
3. Electron Transport Chain:
The high-energy electrons from NADH and FADH_2 are transferred to the electron transport chain, which is located in the inner mitochondrial membrane. As electrons pass along this chain, they move from higher to lower energy states, and the energy released is used to pump protons across the membrane, creating a proton gradient.
4. ATP Synthesis:
The energy stored in this proton gradient is then used by ATP synthase to produce ATP from ADP and inorganic phosphate. This process is known as oxidative phosphorylation.
To summarize, throughout the stages of glycolysis, the citric acid cycle, and the electron transport chain, the energy originally stored in the chemical bonds of glucose is ultimately transferred to ATP. ATP is the primary energy carrier in cells and provides the energy necessary for various cellular activities.
So, the correct answer to the question is:
- The energy is transferred to ATP.
