Metabolic Pathways Linked reactions, one reaction leads to

another Enzyme – organic catalyst (speeds chemical

reaction) Ribozymes – made of RNA, not proteins,

biological catalyst (RNA/protein synthesis) Substrates – reactants in reaction, act on

enzymes

-E -

Activation energy – energy needed to start a reaction

Enzymes lower the amount of activation needed in a reaction

Active site – area on enzyme that the substrate binds to.

Induced fit model- enzyme complex undergoes a slight change in shape

Degradative reactions – substrate broken down Synthesis reaction – substrates combine, larger

product Enzymes are not used up in the reaction, available to

bind to another substrate. Reactions require specific enzymes Enzymes are sometimes named for their substrates,

usually end in -ase

Factors that affect speed of enzyme Substrate concentration Temperature and pH – leads to denaturing Enzyme concentration

Cofactors – inorganic ion (copper,zinc or iron) Coenzymes - nonprotein organic molecule

Vitamins

Enzyme Inhibition Inhibitor binds to enzyme Usually reversible Feedback inhibition – final product of

pathway inhibits a reaction Competitive inhibition – substrate and

competitor bind, only substrate produces Noncompetitive inhibition – inhibitor attaches

to allosteric site, enzymes changes shape

Redox reactions Permits flow of energy to all living things Oxidation – loss of electrons Reduction – gain of electrons Photosynthesis – H+’s, transferred with e’s

coenzyme NADP+ - NADPH Cellular respiration –

Coenzyme NAD+ - NADH (accepts 2e’s and H+)

Cont’d redox reaction examples Electron Transport Chain

Series of membrane-bound carriers, pass e’s from one carrier to another.

Photosynthesis/thylakoid membrane Cellular respiration/cristae – inner membrane of mito.

ATP Production ATP synthase complexes – carrier proteins and enzymes Chemiosmosis – production of ATP due to H+ gradient

across a membrane