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 eReduction: gain of ePhotosynthesis 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