Cellular respiration uses one glucose molecule to produce a total of
a. 2 ATPs.
b. 36 ATPs
c. 24 ATPs
d. 38 ATPs
c. 24 ATPs
To determine the answer, we need to understand the process of cellular respiration and the number of ATP molecules produced at each step.
Cellular respiration is a series of metabolic reactions that occur within cells, converting glucose and oxygen into carbon dioxide, water, and energy in the form of ATP (adenosine triphosphate). The process is divided into three main stages: glycolysis, the Krebs cycle (also known as the citric acid cycle or TCA cycle), and oxidative phosphorylation (including the electron transport chain).
Let's break down each stage and the ATP yield:
1. Glycolysis: This is the initial step of cellular respiration and occurs in the cytoplasm. It converts one molecule of glucose into two molecules of pyruvate, producing a small amount of ATP. Glycolysis directly generates a net yield of 2 ATP molecules per glucose molecule.
2. Krebs cycle: After glycolysis, pyruvate undergoes a series of reactions leading to the Krebs cycle, which takes place in the mitochondria. During the Krebs cycle, the products of glucose breakdown are further metabolized, releasing carbon dioxide and producing electron carriers such as NADH and FADH2. The Krebs cycle itself does not produce ATP directly.
3. Oxidative phosphorylation: This is the final step of cellular respiration and occurs in the inner mitochondrial membrane. The electron carriers (NADH and FADH2) produced during glycolysis and the Krebs cycle donate their electrons to the electron transport chain (ETC). The ETC creates a proton gradient across the mitochondrial membrane and generates ATP through a process known as chemiosmosis. In this step, each NADH molecule can produce approximately 2.5 ATP molecules, while each FADH2 molecule produces approximately 1.5 ATP molecules.
Considering these ATP yields, we can calculate the total ATP production from one glucose molecule:
Glycolysis: 2 ATP
Krebs cycle: No direct ATP production
Oxidative phosphorylation:
- NADH (from glycolysis): Approximately 2.5 ATP per NADH = 2.5 ATP
- NADH (from Krebs cycle): Approximately 2.5 ATP per NADH = 5 ATP
- FADH2: Approximately 1.5 ATP per FADH2 = 1.5 ATP
Total ATP production from one glucose molecule = 2 ATP + 2.5 ATP + 5 ATP + 1.5 ATP = 11 ATP
Therefore, the correct answer is not among the options provided. The closest value to the actual ATP yield from one glucose molecule is approximately 11 ATP, based on the calculations above.
Cellular respiration is a metabolic process that converts glucose into usable energy in the form of ATP (adenosine triphosphate). The correct answer is:
c. 24 ATPs
During cellular respiration, one glucose molecule is broken down into two pyruvate molecules through a process called glycolysis. This process occurs in the cytoplasm and generates a net of 2 ATP molecules.
The pyruvate molecules then enter the mitochondria and undergo further breakdown through the Krebs cycle (Citric Acid Cycle) and oxidative phosphorylation. These processes occur within the mitochondria and result in the production of an additional 32 ATP molecules.
Therefore, the total number of ATP molecules produced from one glucose molecule through cellular respiration is 2 ATPs from glycolysis + 32 ATPs from the Krebs cycle and oxidative phosphorylation, which equals 34 ATPs. However, it's important to note that some sources may round up this number to 36 ATPs to account for other factors and inefficiencies in the process.