Chapter 6~ An Introduction to Metabolism

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; release energy

Anabolic pathways: building process such as protein synthesis; photosynthesis; consume energy

Thermodynamics

Energy (E)~ capacity to do work; Kinetic energy~ energy of motion; Potential energy~ stored energy

Thermodynamics~ study of E transformations

1st Law: conservation of energy; E transferred/transformed, not created/destroyed

2nd Law: transformations increase entropy (disorder, randomness)

Result: quantity of E is constant, quality is not

Spontaneous Change (Reaction)

Nature Runs Downhill

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

Exergonic vs Endergonic Reactions

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

ATP Energy Cycle

Enzymes

Catalytic proteins : change the rate of reactions w/o being consumed

Free E of activation (activation E): the E required to break bonds

Substrate : enzyme reactant

Active site : pocket or groove on enzyme that binds to substrate

Induced fit model

How Enzymes Work

Effects on Enzyme Activity

Temperature and pH (control of enzyme by controlling conditions)

Cofactors: inorganic, nonprotein helpers; ex.: zinc, iron, copper

Coenzymes: organic helpers; ex.: vitamins

Allosteric Enzymes

Enzyme Inhibitors

Irreversible (covalent); reversible (weak bonds)

Competitive : competes for active site (reversible); mimics the substrate

Noncompetitive : bind to another part of enzyme (allosteric site) altering its conformation (shape); poisons, antibiotics

Feedback Inhibition

Cooperativity

Catalase Lab