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Energy and Metabolism

Energy is defined as the capacity to do work, existing in two main forms: kinetic (movement) and potential (stored energy). The concept of metabolism encompasses catabolism (breaking down molecules to release energy) and anabolism (using energy to build complex molecules).

Free Energy

Free energy ($riangle G$) is the capacity of a system to do work, calculated using the equation $riangle G = riangle H - T riangle S$, where $riangle H$ is the change in enthalpy, $T$ is temperature, and $riangle S$ is the change in entropy. A decrease in free energy indicates a spontaneous process.

ATP: The Energy Currency

Adenosine Triphosphate (ATP) serves as the primary energy currency in cells, coupling exergonic reactions (energy-releasing) to endergonic reactions (energy-consuming). ATP hydrolysis, through breaking the terminal phosphate bond, releases energy that powers cellular work like mechanical, transport, and chemical processes.

Enzymes: Catalysts of Metabolism

Enzymes are biological catalysts that lower activation energy, facilitating metabolic reactions by stabilizing transition states. They exhibit specificity for substrates and are not consumed in the reaction. Different types of inhibition exist, including competitive inhibition (where an inhibitor competes with the substrate for binding) and allosteric inhibition (where binding at a site other than the active site alters enzyme activity). Feedback inhibition regulates metabolic pathways, where the end product inhibits an upstream process to maintain homeostasis.