adenosine triphosphate (ATP) - main energy currency used in cells
- made of ribose, adenine (w/ 2 C-N rings), triphosphate group
- adenine forms the base, attracting hydrogen ions
- phosphates joined by unstable bonds, repelling each other
- energy of repulsion stored in bonds that hold phosphates together
- transferring a phosphate group transfers energy
- bonds easily broken, easily turned into adenosine diphosphate (ADP)
- nearly all endergonic reactions require less energy than provided by cleavage of ATP
- enzymes catalyzing endergonic reactions have 2 binding sites: 1 for reactant, other for ATP
- most cells only contain a few seconds' supply of ATP at a time
metabolism - all chemical reactions carried out by an organism
- anabolism - reactions that use energy to make/change bonds
- catabolism - reactions that produce energy when breaking chemical bonds
biochemical pathways - sequence of reactions; organizational metabolic units
- product of 1 reaction becomes substrate for next reaction
- evolved from a need of certain substances (new reactions would start when a certain substance was lacking)
- wasteful if more compounds than needed were produced
- feedback inhibition - where final product acts as an inhibitor on the chemical pathway, shutting it off when enough product has been created
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