An Introduction to Metabolism Bioenergetics Enzymes

Thermodynamics Energy (E)~ capacity to do work; Kinetic energy~ energy of motion; Potential energy~ stored energy Thermodynamics~ study of Energy transformations 1st Law: conservation of energy; E transferred/transformed, not created/destroyed 2nd Law: transformations increase entropy (disorder, randomness)

- G + G A few more definitions….. G = H – T S ENTROPY (S) – the degree or measure of disorder FREE ENERGY (G) – energy which is available to do work TOTAL ENERGY (H) – all energy (including that not available for work) So…. H = G + S And more applicable to us is that: G = H – T S - G EXERGONIC- a reaction that releases any free energy + G ENDERGONIC- a reaction that absorbs/stores free energy

Metabolism/Bioenergetics Metabolism: The totality of an organism’s chemical processes; managing the material and energy resources of the cell Catabolic pathways: degradative process such as cellular respiration; releases energy Anabolic pathways: building process such as protein synthesis; photosynthesis; consumes energy

Free energy Free energy: portion of system’s E that can perform work (at a constant T) Exergonic reaction: net release of free E to surroundings Endergonic reaction: absorbs free E from surroundings

Energy Coupling & ATP E coupling: use of exergonic process to drive an endergonic one (ATP) Adenosine triphosphate ATP tail: high negative charge ATP hydrolysis: release of free E Phosphorylation (phosphorylated intermediate)~ enzymes

Enzymes Catalyst- any chemical agent that accelerates a reaction and is NOT consumed by that reaction. (can be reused) Enzyme- Biological catalysts, usually proteins that help to lower the activation energy of or facilitate a reaction. “-ase” endings Substrate: enzyme reactant. It’s what a particular enzyme acts upon Active site: pocket or groove on enzyme that binds to substrate Induced fit model: As substrate binds, it “induces” the enzyme to change shape.

Effects on Enzyme Activity Temperature- the “goal” is greatest number of collisions with out denaturing. pH-most enzymes have an optimal pH of 6-8 (but some digestive enzymes much lower) Cofactors: nonprotein/inorganic helpers ex.: zinc, iron, copper May bind to enzyme, substrate, or both Coenzymes:organic helpers; ex.: vitamins WebLink

Enzyme Inhibitors WebLink Certain chemicals which prevent enzyme activity Irreversible (covalent); reversible (weak bonds) Competitive: competes for active site; mimics the substrate Can usually be overcome by increasing the substrate. Noncompetitive: bind to another part of enzyme (allosteric site) altering its conformation. The binding of an ACTIVATOR stabilizes the active form The binding of an INHIBITOR stabilizes the inactive form Cooperativity: when a substrate binding to one subunit enhances the bind capabilities of the remaining subunits…. WebLink