METABOLISM: Greek: to change The chemical rxns taking place w/in a cell Catabolism: breaking down molecules to generate E Anabolism: construction of larger molecules (e.g. protein synthesis) and using E Often coupled, see below

Living things require Energy

Energy = capacity to do work

Potential: stored E, ball at top of hill Kinetic: E of motion, ball rolling down hill

Food consumed is chemical E as Potential converted to Kinetic as mechanical

Laws of Thermodynamics First: E cannot be created or destroyed but can be converted from one form to another Conservation of E Second: changing forms of E results in a loss of E – increasing disorganization = Entropy Cellular E transformations (e.g. Na / K pump) result in loss of E Heat is the least organized form of E

Diffusion releases E as solute becomes randomly distributed Glucose hydrolysis results in more, smaller, and more stable molecules

Are living things not examples of increased order, rather than disorder? At an E cost Macromolecules a cell builds will, over time, tend to break down, but slowly at cell temp

Potential = stored Chemical Kinetic = motion Mechanical

Free E = G = part of a system’s E available for work at constant temp A measure of instability

G = H – TS H=total E, S=entropy, T=temp, Kelvin Energy Transformation Exergonic Reaction: E released, negative delta G Reaction will happen spontaneously, no outside help But often requires help at biological temperatures Free E, G, released, therefore, delta G is negative Water flows downhill Endergonic Rxn: E required, positive delta G Protein synthesis, muscle contraction, an “uphill” process Equilibrium: delta G = 0

Glucose, MW = 180g, -686kcal / mol Mole: # grams comprising a molecule’s (or atom’s) MW (or atomic weight) in daltons. Avogadro’s number, 6.023 X 10^23

ATP: the universal E currency of Biology Which class of macromolecules does this belong to? Adenine (N base), Ribose, 3 Phosphates Used in many rxns, provides the required amount of E for many biological functions Used to do work: Chemical: synthesize macromolecules for cell function Transport: of compounds across membranes Mechanical: contraction, movement The triphosphate bond is not strong resulting in available E, it is weak, a loaded spring

Metabolic Pathways Because delta G = 0 at eq, a cell maintains some diseq thru metabolic pathways Product of one rxn becomes substrate of next, along a sequence = pathway Respiration: a series from glucose to CO2 A steady intake of glucose and ability to release CO2 will maintain pathway

Enzymes: catalyze, enhance speed, of these reactions by lowering Ea Many respiratory rxns are coupled Activation Energy, Ea, or delta G++ A rxn involves breaking molecular bonds and forming new ones Requires an initial E investment, Ea Transition state Heat will favor formation of more stable bonds and release of E, but can kill cells Ea is lowered in presence of an enzyme A spark plug Doesn’t change delta G, does not induce spontaneity

Enzymes Are specific to rxns, have shapes with active sites specific to substrate Induced fit and generally held by H bonds May result in degradation of one molecule or rxn between 2 or more Catalysis happens at ~1,000 molecules / second

Factors Affecting Speed of Enzyme Activity [substrate], pH, temp, salinity, cofactors, inhibitors Cofactor – inorganic Coenzyme – organic, e.g. vitamins Inhibitors: reversible and irreversible, based on bond types Competitive: at active site Noncompetitive: at another site on enzyme, allosteric site Can be activators or deactivators Can be poisons: DDT, parathion, penicillin Feedback Inhibition: metabolic pathway switched off by products Phosphorylation (e.g. Na / K pump), can activate enzymes and involve E input Some hormones are detected by membrane receptor proteins and P-late enzymes

Enzymatic catalyzed rxns tend to happen in specific locations w/in cell It’s not a random series of reactions w/o order Oxidation / Reduction Oxidation: loss of e- Reduction: gain of e- Photosynthesis reduces CO2 and oxidizes H2O to form glucose and O2 CO2 + H2O + E  glucose + O2 NADP+ is photosynthesis coenzyme aiding oxidation and reduction of substrates and products Respiration is the reverse, glucose oxidized, O2 reduced, forming CO2, E, and water NAD+ is respiration coenzyme

Electron Transport Series of carriers transferring an initial high E e- to a final low E e-, and generating ATP Carriers are reduced and then oxidized during e- transport steps. Occurs in thylakoids and cristae Results in a buildup of protons during redox and an electrochemical gradient Proton pump and ATP synthase are membrane proteins Chemiosmosis: ATP generation by ATP synthase and proton gradient

Emergent Properties We’ve seen chemistry of macromolecules Cell and cell membrane structures Peculiar properties of water None is simply the sum of its parts