Campbell Biology Chapter 8

metabolism

the totality of an organism's chemical reactions

metabolic pathway

a series of chemical reactions that begins with a specific molecule, which is then altered in a series of steps catalyzed by specific enzymes, resulting in a certain product

catabolic pathway (breakdown pathway)

metabolic pathway that releases energy by breaking down complex molecules into smaller, simpler compounds

ex/ cellular respiration (organic fuels break down to CO₂ and water)

anabolic pathway (biosynthetic pathways)

metabolic pathway that consumes energy to build complex molecules from simpler ones

ex/ protein from amino acids

bioenergetics

the study of how energy flows through living organisms

energy

the capacity to cause change; exists in various forms, some perform work; the ability to rearrange a collection of matter

kinetic energy

energy associated with motion

heat (thermal energy)

kinetic energy associated with the random movement of atoms or molecules

potential energy

energy that matter possesses because of its location or structure

chemical energy

the potential energy available for release in a chemical reaction due to the molecule's structure

thermodynamics

the study of energy transformations

(system [matter under study, can be isolated/open] vs. surroundings)

first law (of thermodynamics)

The principle of conservation of energy: Energy can be transferred and transformed, but it cannot be created or destroyed.

enthropy

a measure of disorder, or randomness;

(appears as increasing amounts of heat and less ordered forms of matter)

second law (of thermodynamics)

Every energy transfer or transformation increases the entropy (disorder) of the universe.

ex/ bear making kinetic energy - produces heat and CO₂ (as it exhales)

spontaneous process

a process that can occur without an input of energy; it is "energetically favorable", it increases entropy of the universe; a process that is moving toward equilibrium

ex/ water flowing downhill

(Gibbs) free energy

the portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system, as in a living cell; measure of a system's instability (tendency to change to stability)

(change in) free energy (∆G)

∆G = ∆H - T∆S

∆G = [final energy] - [initial energy]

equilibrium

maximum stability; ∆G = 0; a cell that is metabolically at this is dead

exergonic reaction

a spontaneous chem reaction with a net release of free energy (also some released as heat); ∆G < 0; the greater the decrease, the greater the amount of work that can be done; reactants have higher free energy, products have less free energy

endergonic reaction

a nonspontaneous chem reaction that absorbs free energy from its surroundings; ∆G > 0, the quantity of energy needed to drive the reaction ("get the reaction to go"); reactants have less free energy, products have more free energy

chemical, transport, mechanical

the three main kinds of work that a cell does/uses ATP for

energy coupling (Rx coupling)

the use of an exergonic process to drive an endergonic one; makes the overall process spontaneous; made possible with ATP hydrolysis

· A+B → C+D ∆G = +5 (endergonic)

· X+Y → Z+W ∆G = -7 (exergonic)

· A+B+X+Y → C+D+Z+W ∆G = -2 (exergonic)

ATP (adenosine triphosphate)

ribose with nitrogenous base adenine and a chain of three phosphate groups; bonds broken through hydrolysis; cycles

7.3 kcal/mol

energy given off in this exergonic reaction (therefore it would be -):

ATP + H₂O → ADP + P + energy;

energy need to drive this endergonic reaction:

ADP + P + energy → ATP

enzyme

a macromolecule (protein) that acts as a catalyst (most ending in -ase);

1. lowers activation energy 2. not used up 3. specific for reaction

catalyst

a chemical agent that speeds up a reaction without being consumed by the reaction

activation energy (Ea)

free energy of activation; energy needed to get the reaction going; the initial investment of energy for starting a reaction, what is required to break the bonds of the reactants

substrate

the reactant an enzyme acts on/binds to

active site

the specific region of an enzyme that binds to the substrate and forms a pocket or groove on the surface in which catalysis occurs

temperature, pH

two factors that affect the activity of an enzyme if anything but the optimal conditions

cofactor

nonprotein enzyme helper that bind tightly to enzyme or loosely and reversibly to the substrate, for proper functioning of the enzyme catalysis; may be inorganic (metal in ionic form) or organic

coenzyme

an organic cofactor

ex/ vitamins

competitive inhibitor

a substance that reduces the productivity of an enzyme by entering the active site in place of the substrate, whose structure it mimics; slows it down, so increase amount of substrate to speed the reaction back up

noncompetitive inhibitor

a substance that reduces the activity of an enzyme by binding to another part of the enzyme (allosteric site), changing the enzyme's shape so that the active site no longer effectively catalyzes the conversion of substrate to product

Vmax

maximum rate of the reaction (with the reaction?)

allosteric regulation

any case in which a protein's function at one site is affected by the binding of a regulatory molecule to a separate site; may result in either inhibition or stimulation of an enzyme's activity

feedback inhibition

a method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway, so the cell does not waste chem resources by making more than necessary

enzyme-substrate complex

what is formed after a substrate binds to an enzyme in its active site (because the enzyme has an induced fit [shape change] around the substrate so it holds it in place)