The process by which ADP is phosphorylated by Pi (inorganic phosphate) to ATP in the electron transport chain… - RRB Nsg. Superintendent-20 July 2019 (Shift-1)

RRB Nsg. Superintendent-20 July 2019 (Shift-1)

Biochemistry & Nutrition

Easy

Appeared in: RRB Nsg. Superintendent-20 July 2019 (Shift-1)

Explanation

The question asks for the specific name of the process where ADP is phosphorylated to ATP within the electron transport chain.
Oxidative phosphorylation is the precise biochemical term for this process, which occurs in the inner mitochondrial membrane.
It couples two events: the oxidation of electron carriers (NADH, FADH₂) in the ETC and the phosphorylation of ADP to form ATP.
This pathway is the most significant source of ATP in aerobic organisms, providing the energy for most cellular activities.

Option B: Oxygenases are enzymes that incorporate oxygen atoms directly into their substrate molecules. This is a different type of biochemical reaction and is not the primary mechanism for ATP synthesis in the ETC.
Option C: Hydroperoxidases, such as catalase and peroxidase, are enzymes involved in the detoxification of reactive oxygen species like hydrogen peroxide. Their role is protective, not energy generation.
Option D: Oxidases are a class of enzymes that use molecular oxygen as an electron acceptor. While Cytochrome c oxidase is a critical oxidase enzyme at the end of the ETC (Complex IV), 'oxidases' is a general category and not the name for the entire process of ATP synthesis.

Visual 1: Diagram of a Mitochondrion. A labeled diagram showing the outer membrane, inner membrane, intermembrane space, and matrix. The location of the Electron Transport Chain complexes and ATP synthase on the cristae (folds of the inner membrane) should be highlighted to provide a clear anatomical context for the process.

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 as background academic context rather than a clinical decision trigger.
Understanding oxidative phosphorylation is crucial as it is the primary energy source for most tissues, especially those with high energy demands like the brain, heart, and skeletal muscle.
Defects in the oxidative phosphorylation pathway, often due to mutations in mitochondrial DNA, can lead to severe multisystem disorders known as mitochondrial diseases (e.g., MELAS - Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like episodes).
What if? If a patient is exposed to cyanide, a potent poison, it specifically inhibits Cytochrome c oxidase (Complex IV) of the ETC. This would halt electron transport, block oxidative phosphorylation, and cause a catastrophic drop in ATP production, leading to rapid cellular hypoxia and death.

How to Approach the Question

First, analyze the question stem to identify the key concepts. The core of the question is 'ADP is phosphorylated... to ATP' and 'in the electron transport chain'.
Recognize that 'phosphorylation' means adding a phosphate group (Pi). The question describes the synthesis of ATP.
The context is the 'electron transport chain', which involves oxidation reactions.
Combine the key concepts: 'oxidation' and 'phosphorylation'. This directly points to 'Oxidative phosphorylation'.
Evaluate the other options. 'Oxidases', 'Oxygenases', and 'Hydroperoxidases' are all types or classes of enzymes, whereas the question asks for the name of a multi-step metabolic process.
Conclude that 'Oxidative phosphorylation' is the only term that describes the entire process of coupling electron transport with ATP synthesis.

Concept Tested & Keywords

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