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Oxidative phosphorylation or synthesis of ATP

Education

Introduction

Hello everyone, this is Dr. P Maran, head of the Department of Biochemistry and Assistant Professor at Jesus College for Women. Today, I will be discussing the topic of oxidative phosphorylation or the synthesis of ATP. Let's dive right in.

Introduction

Oxidative phosphorylation is the process in which electrons are transferred through the electron transport chain to release energy. This energy is used to synthesize ATP from ADP and inorganic phosphate. The exact site of ATP synthesis is complex five, which is located in the inner mitochondrial membrane.

P-to-O Ratio

The P-to-O ratio refers to the number of inorganic molecules used for ATP synthesis for every atom of oxygen consumed. It represents the number of ATP molecules synthesized per pair of electrons transferred through the electron transport chain. For example, a P-to-O ratio of three indicates that three ATP molecules are generated during the mitochondrial oxidation process.

Sites of Oxidative Phosphorylation

There are three main reactions in the electron transport chain that contribute to the synthesis of ATP. The first site is the oxidation of FMNH2 by coenzyme Q, followed by the oxidation of cytochrome B and cytochrome C1, which results in proton pumping. Lastly, the cytochrome oxidase reaction also involves proton pumping, leading to ATP synthesis.

Energetics of Oxidative Phosphorylation

As electrons are transported from NADH to the final acceptor, which is half a molecule of oxygen and water, a redox potential difference is created. This energy difference is around 1.14 volts, equivalent to 52 calories per mole. Each ATP molecule contains 7.3 calories of energy, so if three ATP molecules are synthesized during the oxidation of a single molecule of NADH, the total energy trapped in ATP is 21.9 calories.

Hypothesis for Oxidative Phosphorylation

Two main hypotheses exist for oxidative phosphorylation: the chemical coupling hypothesis and the chemiosmotic hypothesis. The chemical coupling hypothesis suggests that phosphorated high-energy intermediates are produced first and then used for ATP synthesis. On the other hand, the chemiosmotic hypothesis proposes that a proton gradient generated by proton pumping through the inner mitochondrial membrane drives the synthesis of ATP.

ATP Synthase - Key Enzyme for ATP Synthesis

ATP synthase, also known as ATP synthetase or F-ATPase, is the key enzyme involved in ATP synthesis. It is located in the inner mitochondrial membrane and consists of two regions: the F0 region, responsible for proton transport, and the F1 region, responsible for ATP synthesis and hydrolysis. The F1 region comprises several subunits, including alpha, beta, gamma, delta, and epsilon.

Paul Boyer's Model for ATP Synthesis

Paul Boyer studied the structure and function of ATP synthase in detail and proposed a model for ATP synthesis. He discovered that the beta subunits of the F1 region undergo conformational changes that allow ATP to bind and get released. These changes occur as the enzyme continuously rotates. For each rotation, three ATP molecules are synthesized.

Keywords

FAQ

  1. What is oxidative phosphorylation?
  2. How is ATP synthesized in oxidative phosphorylation?
  3. What is the P-to-O ratio?
  4. What are the sites of oxidative phosphorylation?
  5. What is the chemiosmotic hypothesis?
  6. What is ATP synthase?
  7. How does ATP synthase work?
  8. What is Paul Boyer's model for ATP synthesis?

Please feel free to refer to the notes and complete the provided assessment. Thank you for watching!