The proton-motive force created by the electrochemical proton gradient is the source of free energy utilized in ATP formation. Describe the two components contributing to the total proton-motive force.
The correct answer and explanation is:
Correct Answer:
The two components contributing to the total proton-motive force are the chemical gradient (ΔpH) and the electrical potential (Δψ) across the inner mitochondrial membrane.
Explanation (300 words):
The proton-motive force (PMF) is the energy stored in the form of an electrochemical gradient of protons (H⁺) across a membrane. In mitochondria, this force is generated by the electron transport chain (ETC) during oxidative phosphorylation. As electrons move through the ETC, protons are actively pumped from the mitochondrial matrix into the intermembrane space, creating a proton gradient.
The PMF has two main components. The first is the chemical gradient, or ΔpH, which arises because protons accumulate in the intermembrane space, making it more acidic relative to the matrix. This pH difference contributes to the free energy by favoring the movement of protons back into the more alkaline matrix, where they are in lower concentration.
The second component is the electrical potential, or Δψ, which results from the separation of charge across the inner mitochondrial membrane. Since protons are positively charged, their movement into the intermembrane space leaves behind a relatively negative charge in the matrix and builds a positive charge outside. This creates a voltage across the membrane, with the matrix being more negative relative to the intermembrane space.
Together, the chemical gradient and the electrical potential create an electrochemical gradient, or PMF, that drives protons back into the matrix through ATP synthase. As protons flow down this gradient, ATP synthase uses the released energy to convert ADP and inorganic phosphate (Pi) into ATP.
The proton-motive force is essential for cellular energy production. Without it, ATP synthesis would not occur efficiently, impairing many energy-dependent processes. Both the ΔpH and Δψ are vital and interdependent, ensuring optimal energy transfer from nutrient oxidation to ATP formation.