Question

During electron transport system (ETS), electron taiqy proceeds from carriers that have redox pcientat: those having redox potential. This electrontraws: down to the energy gradient leads to the formationdf from ADP and \(\mathrm{Pi}\), which is referred to as (a) Low, high, oxidative phosphorylation (b) Low, high, oxidative decarboxylation (c) High, low, oxidative phosphorylation (d) High, low, oxidative decarboxylation

Short answer

The correct answer is (a) Low, high, oxidative phosphorylation, since electrons flow from carriers with a low redox potential to those with a high redox potential, and the process is known as oxidative phosphorylation.

Step-by-step solution

Understand the Electron Transport System (ETS)

The Electron Transport System (ETS) is a series of complexes located in the inner mitochondrial membrane. Electrons are transferred through these complexes from electron donors to electron acceptors. The flow of electrons down their energy gradient facilitates the process of ATP formation from ADP and inorganic phosphate (Pi).

Determine the Direction of Electron Flow Based on Redox Potential

Redox potential is a measure of the tendency of a chemical species to acquire electrons and thereby be reduced. Electrons in ETS move from carriers with a lower redox potential (less affinity for electrons) to carriers with a higher redox potential (greater affinity for electrons).

Identify the Process Coupled with the Electron Transfer

The energy released from the electron transfer during the ETS is used to synthesize ATP from ADP and Pi. This process is called oxidative phosphorylation. It's not called oxidative decarboxylation since decarboxylation refers to the removal of a carboxyl group and does not necessarily involve the phosphorylation or ATP synthesis.

Key concepts

Oxidative Phosphorylation

Oxidative phosphorylation is the process by which the energy derived from the electron transport system (ETS) is used to generate adenosine triphosphate (ATP), the primary energy currency of the cell.

This complex biochemical process takes place in the mitochondria and it consists of two main parts: the ETS and ATP synthase. During the ETS, electrons are transferred from electron donors, such as NADH and FADH2, to electron acceptors through a series of redox reactions. These electrons flow through a sequence of protein complexes embedded in the inner mitochondrial membrane, finally transferring to oxygen, the terminal electron acceptor, and forming water.

As electrons move from carriers of lower redox potential to those with higher redox potential, protons are pumped across the membrane, creating an electrochemical gradient known as the proton motive force. This force is then utilised by ATP synthase to phosphorylate ADP, turning it into ATP.

Oxidative phosphorylation is efficient and produces the majority of ATP in aerobic organisms. This intricate process is vital for energy production, and any disruptions can have significant impacts on the organism's health and function.

Redox Potential

Redox potential, also referred to as reduction potential, is a measure of a molecule's ability to gain electrons in a redox reaction. A higher redox potential indicates a greater affinity for electrons, whereas a lower redox potential suggests a lesser affinity.

In the context of the electron transport system, redox potential dictates the direction of electron flow. Electrons travel spontaneously from carriers with lower redox potential to those with higher redox potential. This movement is driven by the carriers' intrinsic properties to achieve a more stable, lower energy state.

The concept of redox potential is crucial because it determines how effectively the ETS can transfer electrons and therefore how efficiently oxidative phosphorylation can occur. When comparing molecules in terms of their redox potential, we consider the standard redox potential, measured under standard conditions, to predict the direction of electron flow in various biological processes.

Understanding redox potential is essential for comprehending how living organisms harvest energy from metabolic processes and for developing technological applications, such as biofuel cells and environmental sensors.

ATP Synthesis

ATP synthesis is the process of creating ATP molecules, which store and transport chemical energy within cells. ATP is synthesized through two primary processes: substrate-level phosphorylation and oxidative phosphorylation, the latter being a part of cellular respiration.

In the mitochondria, after the electron transport chain establishes a proton gradient, ATP synthesis occurs via ATP synthase. This enzyme uses the energy from the electrochemical proton gradient to catalyze the combination of ADP and inorganic phosphate (\( \text{Pi} \)) to form ATP.

The process is somewhat like a hydroelectric dam, where the flow of water through turbines generates electricity. Similarly, in ATP synthesis, the flow of protons through ATP synthase drives the production of ATP. ATP is then utilized for numerous cellular activities, including muscle contraction, nerve impulse propagation, and chemical synthesis.

Every day, a human body synthesizes and consumes about its body weight in ATP, though a single molecule is recycled 1000-1500 times a day, highlighting the efficiency of the ATP synthesis mechanism.