Which process is responsible for synthesis of ATP in mitochondria

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2024

Biochemistry & Nutrition

Easy

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2024

Explanation

Oxidative phosphorylation is the primary metabolic pathway responsible for synthesizing the majority of ATP in eukaryotic cells.
This process occurs specifically on the inner mitochondrial membrane, utilizing enzymes of the electron transport chain and ATP synthase.
It couples the oxidation of reduced coenzymes (NADH and FADH2) with the phosphorylation of ADP to ATP.
The chemiosmotic hypothesis explains this process, where a proton gradient across the inner mitochondrial membrane drives ATP synthesis.
It is the most efficient stage of cellular respiration, producing approximately 28-34 molecules of ATP per molecule of glucose.

Option A: Glycolysis occurs in the cytoplasm, not the mitochondria. It yields only a small net amount of ATP (2 molecules per glucose).
Option B: The Krebs cycle occurs in the mitochondrial matrix but directly produces only a small amount of ATP (as GTP). Its primary role is to generate NADH and FADH2 for the electron transport chain.
Option C: Beta oxidation is the catabolic process for breaking down fatty acids. It does not directly synthesize ATP but produces acetyl-CoA, NADH, and FADH2 which then enter the Krebs cycle and oxidative phosphorylation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Cellular respiration and ATP synthesis pathways as background academic context rather than a clinical decision trigger.
Understanding ATP synthesis is crucial for comprehending mitochondrial diseases, where defects in oxidative phosphorylation lead to severe energy deficits affecting muscles, brain, and heart.
Poisons like cyanide and carbon monoxide are lethal because they inhibit components of the electron transport chain, halting oxidative phosphorylation and causing rapid cellular death.
What if? - If a patient ingests a poison like oligomycin, which inhibits ATP synthase, the proton gradient would build up but no ATP would be produced. This would stop the electron transport chain and lead to a fatal energy crisis, even with ample oxygen and fuel.

How to Approach the Question

First, identify the key phrases in the question: 'synthesis of ATP' and 'in mitochondria'. This sets the context for both the process and its location.
Evaluate each option based on its known location and primary function in metabolism.
Eliminate 'Glycolysis' because it occurs in the cytoplasm, not the mitochondria.
Consider the remaining mitochondrial processes. Recall that the 'Krebs cycle' and 'Beta oxidation' are primarily for breaking down fuel molecules to produce electron carriers (NADH, FADH2) and acetyl-CoA.
Recognize that 'Oxidative Phosphorylation' is the specific, large-scale process that uses the products of the other pathways (electron carriers) to generate the vast majority of ATP.
Conclude that Oxidative Phosphorylation is the direct answer to the question about the main ATP synthesis process in mitochondria.

Concept Tested & Keywords

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E6 Biochemistry U Satyanarayana— Part 1 (pp 26-420 of 840) p. 222-224

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 1 (pp 26-370 of 370) pp. 118-120, 140-142