begins with a specific molecule, which is then altered in a series of defined steps, resulting in a certain product

metabolic pathways release energy by breaking down complex molecules to simpler compounds

consume energy to build complicated molecules from simpler ones; they are some- times called biosynthetic pathways

example: the synthesis of an amino acid from a simple molecule to a protein from an amino acid

energy is the capacity to cause change

energy associated with the relative motion of an object

example:the motion of the cue stick to push the cue ball, which in turn moves the other balls

is kinetic energy associated with the random movement of atoms or molecules; thermal energy in transfer from one object to another is called heat

an object not presently moving may still possess energy

it is energy that matter possesses because of its location or structure

example:Water behind a dam, for instance, possesses energy because of its altitude above sea level

refers to the potential energy available for release in a chemical reaction

cells do chemical, transport, and mechanical work

cells manage their energy resources to do work by energy coupling, the use of an exergonic process to drive an endergonic one

ATP (adenosine triphosphate) is responsible for mediating most energy coupling in cells

during chemical work, the pushing of endergonic reactions that would not occur spontaneously, such as the synthesis of polymers from monomers

during transport work, the pumping of substances across membranes against the direction of spontaneous movement

during mechanical work, the contraction of muscle cells, and
the movement of chromosomes during cellular reproduction

ATP contains sugar ribose, with the nitrogenous base adenine and a chain of three phosphate groups (the triphosphate group) bonded to it

with help of some enzymes, cells are able to use energy released by ATP hydrolysis directly to drive chemical reactions

the key to coupling exergonic and endergonic reactions is the formation of as phosphorylated intermediate

enzymes are a macromolecule that act as a catalyst, a chemical agent that speeds up a reaction without being consumed by the reaction

without enzymes chemical traffic through the pathways of metabolism would become terribly congested because many chemical reactions would take such a long time

enzymes lower the activation energy of a chemical reaction so it will speed up the reaction.

the reactant of an enzyme acts on is referred to as the enzyme’s substrate

enzyme binds to its substrate (or sub- strates, when there are two or more reactants), forming an enzyme-substrate complex

while enzyme and substrate are joined, the catalytic action of the enzyme converts the substrate to the product (or products) of the reaction

Only a restricted region of the enzyme molecule actually binds to the substrate, this region is the active site