AP Bio Unit 3

kinetic energy

associated with movement

potential energy

stored energy; it depends on the structure of an object or its position relative to its surroundings

chemical energy

form of potential energy held in the bonds of molecules

first law of thermodynamics

energy cannot be created or destroyed

second law of thermodynamics

there is an increas in entropy in the universe over time

entropy

the degree of disorder or a measure of the number of positions and motions a molecule can take

chemical reactions

involve the breaking and forming of bonds

gibbs free energy (G)

amount of energy available to do work

exergonic reactions

spontaneous (change in G < 0) and release energy

endergonic reactions

non-spontaneous (change in G > 0) and require energy

hydrolysis of ATP

exergonic reaction that drives many endergonic reactions in a cell

enzymes

proteins that act as biological catalysts

• reduce free energy level of the transition state between reactants and products, reducing energy inout, or activation energy required

• increasing temp, increases activity

• narrow pH

• too hot denatures

transient covalent bonds or weak noncovalent interactions

stabilize the complex between the substrate, product, and enzyme

activators

increase the activity of enzymes

inhibitors

reduce the activity of enzymes

allosteric enzymes

bind activators and inhibitors at sites others than the active site, resulting in a change in their shape and activity

• found at our near the start of a metabolic pathway

oxidation-reduction (redox) reactions

transfer electrons and energy

oxidation reaction

chemical reactions in which molecules lose electrons and energy

• in photosynthesis, water is oxidized releasing oxygen

reduction reaction

chemical reactions in which molecules gain electrons and energy

• in photosynthesis, carbon dioxide is reduced, forming carbohydrates

light reactions

• first step of photosynthesis

• occurs in the thylakoid

• light from sun splits water apart

• electrons from water are used for ATP and NADPH

• oxygen is released

photosynthetic electron transport chain

a series of electron transfer or redox reactions

• water is electron donor and NADP+ is electron acceptor

• consists of photosystem 1 and 2

photosystem II

pulls electrons from water, resulting in the production of oxygen

• occurs before photosystem I

photosystem I

reduces NADP+ and produces NADPH