BIOL 1010 Lecture Notes - Exergonic Reaction, Electronegativity, Redox
Document Summary
Organism live at the expense of free energy. The maximum amount of usable energy that can be harvested from a particular reaction is the system"s free energy change from initial to the final state. This change in free energy ( g) is given by the gibbs-helmholtz equation at constant temperature and pressure: In passive transport, a substance diffuses spontaneously down its concentration gradient with no need for the cell to expend energy. Hydrophobic molecules and very small uncharged polar molecules diffuse directly across the membrane. Hydrophilic substances diffuse through transport proteins in a process called facilitated diffusion. In active transport, a transport protein moves substances across the membrane uphill against their concentrations gradients. Active transport requires an expenditure of energy usually supplied by. Proton pumps are examples of membrane proteins that store energy by generating voltage (charge separation) across substances. Using atp for power, a proton pump translocates positive charge in the form of hydrogen ions.