Problem 28 - Objective Biology for NEET

Question

How many molecules of ATP are produce by oxidation of 1 molecule of glucose? (a) 30 (b) 36 (c) 4 (d) 40

Step-by-Step Solution

Answer

The correct answer is (b) 36.

Step 1: Understand cellular respiration

Cellular respiration is the process that releases energy by breaking down glucose in the presence of oxygen. The stages including Glycolysis, Pyruvate Decarboxylation, Krebs Cycle, and Oxidative Phosphorylation are all crucial for production of ATP.

Step 2: Calculate ATP from glucose

The Oxidation of one glucose molecule produces ATP in these stages. Glycolysis produces 2 ATP, Krebs cycle also gives 2 ATP. The electron transport chain gives about 32 ATP. The total would be 2 (from Glycolysis) + 2 (from Krebs Cycle) + 32 (from Electron transport chain) = 36 ATP.

Key Concepts

Cellular Respiration

Cellular respiration is a vital biological process that provides energy to cells. It converts glucose (a simple sugar) into adenosine triphosphate (ATP), the energy currency of the cell. This process occurs in the mitochondria of eukaryotic cells. Cellular respiration involves various stages:

• Glycolysis
• Krebs Cycle
• Oxidative Phosphorylation (Electron Transport Chain)

Each stage contributes to the production of ATP by breaking down glucose and transferring the energy to ATP molecules. Cellular respiration is aerobic, meaning it requires oxygen to efficiently produce energy. This process is essential for cellular functions, growth, and maintenance.

Glycolysis

Glycolysis is the first stage of cellular respiration and occurs in the cytoplasm of the cell. During glycolysis, one molecule of glucose is broken down into two molecules of pyruvate. This process results in the production of 2 ATP molecules and 2 NADH (a type of energy carrier).

• Glycolysis does not require oxygen (anaerobic process)
• It generates energy quickly, but in smaller amounts than the following stages
• Produces 2 net ATP molecules

The pyruvate molecules created in this process will move into the mitochondria, where they are further processed in the Krebs cycle. Despite the modest ATP yield, glycolysis is crucial because it sets the stage for more energy extraction processes to occur.

Krebs Cycle

The Krebs Cycle, also known as the Citric Acid Cycle, occurs in the matrix of the mitochondria. It processes the pyruvate molecules generated from glycolysis to yield more energy carriers and a small amount of ATP. Here's a closer look:

• Two ATP molecules are produced for each glucose molecule
• NADH and FADH2 are generated, which are crucial for the next stage
• Carbon dioxide is released as a waste product

The Krebs Cycle plays a key role in breaking down carbon compounds and capturing high-energy electrons in the form of NADH and FADH2. These carriers will then be used in oxidative phosphorylation to produce a significant amount of ATP.

Oxidative Phosphorylation

Oxidative phosphorylation is the final and most productive stage of cellular respiration. It takes place in the inner mitochondrial membrane, where electron carriers from the Krebs cycle—NADH and FADH2—facilitate this process:

• Electrons are transferred through a series of proteins known as the electron transport chain
• Energy from these electron transfers is used to pump protons, creating a gradient
• This gradient powers ATP synthase to convert ADP to ATP
• Approximately 32 ATP molecules are produced from one glucose molecule during this stage

The process ends when electrons combine with oxygen and hydrogen to produce water. Oxidative phosphorylation makes the largest ATP contribution out of all stages, highlighting the need for oxygen in efficiently harvesting energy from glucose.