Question

Net Equation for Glycolysis and the Citric Acid Cycle Write the net biochemical equation for the metabolism of a molecule of glucose by glycolysis and the citric acid cycle, including all cofactors.

Short answer

The net equation is: \(C_6H_{12}O_6 + 10 \text{NAD}^+ + 2 \text{FAD} + 4 \text{ADP} + 4 \text{P}_i + 2 \text{H}_2O \rightarrow 6 \text{CO}_2 + 10 \text{NADH} + 10 \text{H}^+ + 2 \text{FADH}_2 + 4 \text{ATP}\).

Step-by-step solution

Understand Glycolysis Overview

Glycolysis is the process where one molecule of glucose (C6H12O6) is broken down in the cytoplasm to produce two molecules of pyruvate. This process generates 2 ATP molecules and reduces 2 NAD+ to 2 NADH.

Identify Glycolysis Net Equation

The net equation for glycolysis starting with glucose is:\[ C_6H_{12}O_6 + 2 ext{ADP} + 2 ext{P}_i + 2 ext{NAD}^+ ightarrow 2 ext{C}_3H_4O_3 (pyruvate) + 2 ext{ATP} + 2 ext{NADH} + 2 ext{H}^+ + 2 ext{H}_2O \]

Understand Citric Acid Cycle Overview

The citric acid cycle, also known as the Krebs cycle, takes place in the mitochondria. Each pyruvate is converted into acetyl-CoA and enters the cycle, producing ATP, NADH, FADH2, and CO2.

Identify Citric Acid Cycle Net Equation

For each glucose molecule, two pyruvate molecules are metabolized through the cycle:\[ 2 ext{C}_3H_4O_3 + 8 ext{NAD}^+ + 2 ext{FAD} + 2 ext{ADP} + 2 ext{P}_i + 2 ext{H}_2O ightarrow 6 ext{CO}_2 + 8 ext{NADH} + 8 ext{H}^+ + 2 ext{FADH}_2 + 2 ext{ATP} + 2 ext{CoA} \]

Combine Glycolysis and Citric Acid Cycle Equations

Add the net equations of glycolysis and the citric acid cycle to get the overall equation:\[ C_6H_{12}O_6 + 10 ext{NAD}^+ + 2 ext{FAD} + 4 ext{ADP} + 4 ext{P}_i + 2 ext{H}_2O ightarrow 6 ext{CO}_2 + 10 ext{NADH} + 10 ext{H}^+ + 2 ext{FADH}_2 + 4 ext{ATP} \]

Confirm the Biochemical Changes

Check that all molecules and ions are balanced on both sides of the equation, ensuring that mass, charge, and atom counts are equal. This confirms all reactants have clearly turned into products.

Key concepts

Citric Acid Cycle

The Citric Acid Cycle, often referred to as the Krebs cycle or TCA cycle, is a crucial metabolic pathway that takes place in the mitochondria. It plays a vital role in cellular respiration, helping to generate energy from carbohydrates, proteins, and fats. When glucose is metabolized through glycolysis, it produces two molecules of pyruvate, which then enter the mitochondria. Here, each pyruvate is converted into acetyl-CoA, which is a key component required to start the Citric Acid Cycle.

In this cycle, for each acetyl-CoA molecule, a series of reactions occur which:

• Release two molecules of carbon dioxide (CO₂).
• Generate three NADH and one FADH₂, which are vital electron carriers.
• Produce one ATP (or GTP, depending on the organism) molecule, which serves as a direct energy source for cells.

The cycle works to convert these energy carriers, NADH and FADH₂, into ATP in the next stage of cellular respiration known as oxidative phosphorylation.

Completing this cycle twice for every glucose molecule (since it produces two pyruvate molecules) is essential for maximizing energy yield within a cell.

Glucose Metabolism

Glucose metabolism is a fundamental process that provides energy to cells throughout the body. It begins with glycolysis, an anaerobic process occurring in the cytoplasm, where a single glucose molecule (C₆H₁₂O₆) is split into two pyruvate molecules. This process yields a small amount of energy: 2 molecules of ATP and 2 NADH molecules, which are used in the mitochondria for further energy production.

Following glycolysis, the resulting pyruvate enters the mitochondria. Here, it is transformed into acetyl-CoA to enter the Citric Acid Cycle where even more energy is extracted. This transition from glycolysis to the citric acid cycle is vital to provide a continuous flow of fuel for high-energy activities.

The complete metabolism of glucose includes:

• Glycolysis - breaking down glucose to pyruvate.
• Pyruvate conversion to acetyl-CoA.
• Citric Acid Cycle - further processing to extract energy-rich NADH and FADH₂.
• Electron transport chain and oxidative phosphorylation - the final step where ATP is generated.

This network of reactions ensures that glucose is efficiently metabolized to maintain energy needs across different tissues in the body.

Biochemical Equation

Biochemical equations are important representations to understand chemical processes within living organisms. These equations help illustrate the transformation of molecules through metabolic pathways, highlighting the conversion of reactants to products. For glucose metabolism, the net biochemical equation combines reactions from both glycolysis and the Citric Acid Cycle.

The full net reaction for glucose metabolism through these pathways is summarized as:\[ C_6H_{12}O_6 + 10 \text{NAD}^+ + 2 \text{FAD} + 4 \text{ADP} + 4 \text{P}_i + 2 \text{H}_2O \rightarrow 6 \text{CO}_2 + 10 \text{NADH} + 10 \text{H}^+ + 2 \text{FADH}_2 + 4 \text{ATP} \]

This equation indicates that a single glucose molecule is converted into carbon dioxide and water, while simultaneously capturing energy in the form of ATP. Additionally, electrons are transferred to the carriers NADH and FADH₂, which play pivotal roles in further energy conversion processes.
Biochemical equations ensure mass, charge, and atom counts are balanced, providing meaningful insights into the efficiency and regulation of cellular metabolic activities.