Metabolism and Energy Reactions

Metabolism: Sum of all chemical reactions in the body.
Metabolic Pathways: Sequential enzyme-catalyzed reactions, beginning with a reactant and ending with a final product.
Regulation: Highly regulated, often by feedback inhibition (end product slows an enzyme early in the pathway).

Definition: Metabolic assistants that speed up chemical reactions, not destroyed in the process.
Substrates: Reactants that enzymes act upon.
Naming: Often named after substrates (e.g., lipase for lipids, lactase for lactose).
Active Site: Specific region where substrates bind and react.
Specificity: Determined by the shape of the active site.
Energy of Activation: Energy required to initiate a reaction. Enzymes lower this energy ( $E_a$ ), thereby increasing reaction rate.
Coenzymes: Non-protein molecules (often derived from vitamins, e.g., niacin in NADP) that assist enzyme activity by accepting or contributing atoms.

Mitochondria: "Powerhouse of the cell"; convert chemical energy of glucose into ATP.
Cellular Respiration: Process where mitochondria use $O<em>2$ and release $CO</em>2$ to produce ATP from glucose.
Structure: Double-membrane organelle; outer membrane and folded inner membrane (cristae) enclosing a gel-like matrix.
- Matrix contains enzymes for glucose breakdown.
- Cristae contain protein complexes for ATP production.

ATP (Adenosine Triphosphate): The cell's energy currency, resembling a rechargeable battery.
Production: Glucose breakdown (cellular respiration) produces ATP from ADP (Adenosine Diphosphate) + inorganic phosphate ( $P_i$ ).
Usage: ATP provides energy for cellular work (e.g., muscle contraction, nerve impulses); breaks down into ADP, $P_i$ , and heat.