In mitochondria, exergonic redox reactions
a. are the source of energy driving prokaryotic ATP synthesis.
b. provide the energy that establishes the proton gradient.
c. reduce carbon atoms to carbon dioxide.
d. are coupled via phosphorylated intermediates to endergonic processes.
The Correct Answer and Explanation is :
The correct answer is b. provide the energy that establishes the proton gradient.
Explanation:
Mitochondria are often referred to as the powerhouses of the cell because they play a crucial role in energy production through the process of cellular respiration. Within mitochondria, exergonic redox reactions occur during the electron transport chain (ETC), which is a series of protein complexes and other molecules located in the inner mitochondrial membrane. These reactions involve the transfer of electrons from electron donors, such as NADH and FADH2, to electron acceptors, ultimately reducing oxygen to form water.
As electrons are transferred through the ETC, energy is released in a series of exergonic (energy-releasing) reactions. This energy is utilized to pump protons (H⁺ ions) from the mitochondrial matrix into the intermembrane space, creating an electrochemical gradient, or proton gradient, across the inner mitochondrial membrane. This gradient is crucial for the synthesis of ATP, as it establishes a potential energy difference between the inside and outside of the membrane.
The stored energy in this proton gradient is harnessed by ATP synthase, an enzyme that allows protons to flow back into the matrix through its structure. As protons flow down their concentration gradient, ATP synthase catalyzes the phosphorylation of ADP to form ATP, a process known as oxidative phosphorylation.
In summary, the exergonic redox reactions in the mitochondria provide the necessary energy to establish the proton gradient, which is essential for ATP production. Without this gradient, ATP synthesis via oxidative phosphorylation would be significantly impaired, highlighting the vital role of these reactions in cellular energy metabolism.