Jawaharlal Nehru Technological University Hyderabad B.Pharmacy II Year BIOCHEMISTRY Previous Question Paper (August/ September- 2022 - R17)

Oxidative phosphorylation occurs in the inner mitochondrial membrane, specifically within the cristae. It involves the transfer of electrons from NADH and FADH2 to oxygen via the electron transport chain, creating a proton gradient that drives ATP synthesis.

The energetics are governed by the chemiosmotic coupling hypothesis. The oxidation of one NADH molecule results in the pumping of 10 protons, yielding approximately 2.5 ATP, while FADH2 results in 6 protons, yielding approximately 1.5 ATP.

The Rotary Rotor Model (Binding Change Mechanism) explains how ATP synthase (F1F0-ATPase) functions:

• The F0 subunit acts as a membrane-bound proton channel. As protons flow through, they cause the c-ring and the attached gamma-subunit (the rotor) to rotate.
• The F1 subunit contains three beta-subunits that exist in three distinct conformational states: Open (O), Loose (L), and Tight (T).
• In the L state, ADP and Pi are trapped. In the T state, they are condensed to form ATP. In the O state, the newly synthesized ATP is released.
• As the gamma-subunit rotates 120 degrees, it forces each beta-subunit to transition through these states sequentially, resulting in the production of three ATP molecules per full 360-degree rotation.

Diagrammatic representation: Imagine a central stalk (gamma-subunit) rotating within a hexagonal ring of alpha and beta subunits. The rotation is driven by the proton motive force acting on the c-ring, which is physically linked to the gamma-stalk.

The pathway of gluconeogenesis proceeds as follows:

• Pyruvate → Oxaloacetate (via Pyruvate carboxylase)
• Oxaloacetate → Phosphoenolpyruvate (via PEP carboxykinase)
• Phosphoenolpyruvate → 2-Phosphoglycerate → 3-Phosphoglycerate → 1,3-Bisphosphoglycerate → Glyceraldehyde-3-phosphate
• Glyceraldehyde-3-phosphate ⇌ Dihydroxyacetone phosphate
• Glyceraldehyde-3-phosphate + Dihydroxyacetone phosphate → Fructose-1,6-bisphosphate
• Fructose-1,6-bisphosphate → Fructose-6-phosphate (via Fructose-1,6-bisphosphatase)
• Fructose-6-phosphate → Glucose-6-phosphate
• Glucose-6-phosphate → Glucose (via Glucose-6-phosphatase)