Chapter 8 Intro to Metabolism

Energy of Life Living cell is a chemical factory - sugars converted to amino acids then linked together to form proteins - proteins broken down to amino acids and converted to sugars upon digestion - Cellular respiration drives cellular economy by extracting energy for various processes such as transport, even converting stored energy to light (bioluminescence) - all metabolic activities carried out by the cell are precisely coordinated and controlled

Organisms’ Metabolism Metabolism manages the material and energy resources of the cell Metabolic pathways- begins with a specific molecule, which is altered in a series of defined steps, and results in a certain end product. *each step is catalyzed by a specific enzyme

Metabolism Catabolic pathways – degradative processes that break down complex molecules into simpler compounds - release energy to drive other processes Ex: Cellular respiration Anabolic pathways – biosynthetic pathways that consume energy to build complicated molecules from simpler ones Ex: polymer macromolecule amino acid protein Bioenergetics – study of how organisms manage their energy resources

Forms of Energy Energy – capacity to cause change - does work, transports or moves matter against opposing forces Ex: gravity & friction -ability to rearrange collection of matter

Forms of Energy Kinetic energy – energy of motion Heat or thermal energy - kinetic energy associated with random movement of molecules or atoms Potential energy – energy stored or possessed by location or structure (resting) Chemical energy – potential energy stored up for release in a chemical reaction (catabolizing glucose)

Laws of Energy Transformation Thermodynamics – study of energy transformations that occur in a collection of matter - system is the matter under study -surroundings: everything outside the system - closed system isolates from the surroundings Ex: coffee in a thermos - open system exchanges energy and matter between itself and its surroundings Ex: organisms absorb energy and release metabolic wastes

Laws of Thermodynamics First Law of Thermodynamics (principle of conservation of energy) – energy of the universe is constant - energy is transferred and transformed, but not created or destroyed Ex:- electricity - light to chemical in photosynthesis - potential to kinetic to potential

Laws of Thermodynamics Second Law of Thermodynamics – energy transfer or transformation increases entropy of the universe *During normal energy transfers, some energy is lost as heat – increases randomness of molecules Entropy – measure of disorder or randomness - heat is the random movement of molecules, and every chemical Rx creates heat as a byproduct - every energy transfer increases entropy of the universe

Spontaneous vs. Nonspontaneous Spontaneous reaction – will occur without input of outside energy and will increase entropy of the universe Ex: rusting car or fireworks Nonspontaneous reaction – requires input of outside energy but increases entropy Ex: water pumped against the force of gravity

Section 8.2 Free Energy

Free Energy Free energy – measures the portion of a systems energy that can perform work when temp. and pressure are uniform throughout the system To measure a change in free energy : -change in G dictates whether a reaction is spontaneous or not *negative G means its spontaneous and the system is losing free energy *positive G means its nonspontaneous and the system is gaining energy

Stability and Equilibrium Organisms prefer to have a lower amount of free energy because it shows stability in the system - work to a point of equilibrium that is spontaneous and able to do work - pushing away from equilibrium will increase free energy but will be nonspontaneous - systems never spontaneous move away from equilibrium

Metabolism Exergonic Rx – proceeds with a net release of free energy (energy outward) - loss means a negative G - spontaneous reaction with great amount of work done Endergonic Rx – proceeds with the absorption of free energy - reaction stores energy - positive G meaning nonspontaneous Rx *if a chemical process is exergonic in one direction then the reverse process is usually endergonic Ex: cellular respiration & photosynthesis Sunlight is source for endergonic reactions

Equilibrium Closed systems eventually reach equilibrium and can not do work Organisms (open systems) are always working toward but never reach equilibrium, as they constantly absorb and release molecules *cells that reach metabolic equilibrium are dead!