[apbio] unit 3 - 3.1-3.3

energy and enzymes

potential energy

stored energy, ex:chemical

kinetic energy

energy of motion, ex:thermal

first law of thermodynamics

energy can be transferred/transformed but cannot be created or destroyed (law of conservation of energy)

second law of thermodynamics

every energy transfer or transformation increases the disorder of the universe. some energy is released as free energy (Gibbs free energy)

chemical reactions

breaking and creating of bonds between different substances (requires energy)

activation energy

amount of energy needed to make a chemical reaction start

reactants

substrate, substances that are changed during a reaction

products

substances that are made by a chemical reaction

metabolism

sum of all chemical reactions occuring in a cell or organism

catabolic reactions

hydrolysis: breaking down macromolecules, small amount of energy needed, more energy released

anabolic reactions

dehydration synthesis: larger molecules form in cells, energy is consumed and stored in the bonds

metabolic pathway

begins with a specific molecule and ends with a product. each step catalyzed by a specific enzyme

catabolic pathways

release energy

ex. cellular respiration

anabolic pathways

consume energy

ex. synthesis of a protein from amino acids

endothermic reactions

absorbs energy

exothermic reactions

releases energy

activation energy

supplies in form of thermal energy that the reactant molecules absorb from their surroundings

endergonic

chemical reactions that require a net input of energy

exogonic

chemical reactions that have a net loss of energy

enzymes

proteins that act as biological catalysts, speed up the rate of chemical reactions by lowering activation energy w/o being consumed or changed

transition state

a large amount of free energy, highly unstable

active site of an enzyme

fits only one substrate (reactant)

lock and key model

substrate fits into the active site like a key fits into a lock

induced-fit model

the binding of a substrate to the active site changes the shape of the active site

high temperatures can cause an enzyme to

denature/unfold/lose its function

activators

increase enzyme activity

inhibitors

reduce enzyme activity (block)

competitive inhibition

competes with the substrate to prevent normal substrate bonding with the active site

non-competitive inhibition

inhibitor bonds to part of the enzyme and changes the shape of the active site. prevents bonding of the substrate, reaction doesnt happen.

feedback inhibition

when the enzymes activity slows down because of negative feedback with the allosteric sites

enzyme rates calculations

rate = dY/dT (slope)