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Glucose catabolism pathways are sequential and lead to the production of ATP. What is the correct order of the pathways for the breakdown of a molecule of glucose as shown in the formula? \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+\mathrm{O}_{2} \rightarrow \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}+\) energy \(\begin{aligned} \text { a. } & \text { oxidative phosphorylation } \rightarrow \text { citric acid cycle } \\ & \rightarrow \text { oxidation of pyruvate } \rightarrow \text { glycolysis } \end{aligned}\) \(\begin{aligned} \text { b. the oxidation of pyruvate } & \rightarrow \text { citric acid cycle } \\ & \rightarrow \text { glycolysis } \rightarrow \text { oxidative phosphorylation } \end{aligned}\) c. glycolysis \(\rightarrow\) oxidation of pyruvate \(\rightarrow\) citric acid cycle \(\rightarrow\) oxidative phosphorylation d. citric acid cycle \(\rightarrow\) glycolysis \(\rightarrow\) oxidative phosphorylation \(\rightarrow\) oxidation of pyruvate

Step by step solution

01

Understand the process of glucose catabolism

Glucose catabolism is the breakdown of glucose molecules to produce energy in the form of ATP. The entire process includes multiple sequential pathways.

02

Identify the pathways involved

The main pathways for the breakdown of glucose to produce ATP are glycolysis, oxidation of pyruvate, citric acid cycle (Krebs cycle), and oxidative phosphorylation.

03

Determine the sequence in which these pathways occur

In glucose catabolism, the sequence of pathways is as follows: Glycolysis is the first step, followed by the oxidation of pyruvate, then the citric acid cycle, and finally, oxidative phosphorylation.

04

Match the sequence with the given options

Compare the correct sequence with the provided options: a. oxidative phosphorylation 鈫� citric acid cycle 鈫� oxidation of pyruvate 鈫� glycolysisb. oxidation of pyruvate 鈫� citric acid cycle 鈫� glycolysis 鈫� oxidative phosphorylationc. glycolysis 鈫� oxidation of pyruvate 鈫� citric acid cycle 鈫� oxidative phosphorylationd. citric acid cycle 鈫� glycolysis 鈫� oxidative phosphorylation 鈫� oxidation of pyruvate

05

Choose the correct option

The sequence glycolysis 鈫� oxidation of pyruvate 鈫� citric acid cycle 鈫� oxidative phosphorylation is found in option c.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

glycolysis

Glycolysis is the first step in the process of breaking down glucose to extract energy. It happens in the cytoplasm of the cell. During glycolysis, one molecule of glucose (6 carbons) is split into two molecules of pyruvate (3 carbons each). This process generates a small amount of energy (2 ATP molecules) and also produces NADH, which stores high-energy electrons. Glycolysis does not require oxygen, making it an anaerobic process. Though the energy yield is lower than in later stages, it's crucial for the initial splitting of glucose into smaller molecules that can enter further stages of glucose catabolism.

oxidation of pyruvate

After glycolysis, the pyruvate molecules enter the mitochondria if oxygen is present to undergo the oxidation of pyruvate. Each pyruvate molecule is converted into Acetyl-CoA, a molecule that can enter the citric acid cycle. This step releases one molecule of carbon dioxide and produces one NADH per pyruvate molecule (so, two NADHs in total from one glucose molecule). Oxygen is not directly used in this step, but the chain reactions that follow depend on its presence. The oxidation of pyruvate is essential for forming Acetyl-CoA, which is needed for the citric acid cycle.

citric acid cycle

The citric acid cycle, also known as the Krebs cycle, takes place in the mitochondrial matrix. This cycle processes Acetyl-CoA to produce ATP, NADH, and FADH2, which are electron carriers. Each turn of the cycle generates two molecules of carbon dioxide and one molecule of ATP. Additionally, three molecules of NADH and one molecule of FADH2 are produced per Acetyl-CoA. Since one glucose yields two Acetyl-CoA molecules, the cycle runs twice for each glucose molecule, doubling the output. The citric acid cycle is a critical stage for energy extraction as it harvests high-energy electrons for use in later stages.

oxidative phosphorylation

Oxidative phosphorylation is the final stage of glucose catabolism, occurring on the inner mitochondrial membrane. This stage includes the electron transport chain and chemiosmosis. NADH and FADH2 produced in earlier steps donate electrons to the electron transport chain, which powers the pumping of protons across the inner membrane, creating a proton gradient. As protons flow back through ATP synthase, energy is captured to produce ATP. Oxygen is vital here, acting as the final electron acceptor, forming water by combining with electrons and protons. This stage generates the most ATP, making it crucial for cellular energy production. Altogether, the entire process efficiently converts the energy stored in glucose into ATP, which cells use to perform various functions.