BIOL 1107 EXAM 2 STUDY GUIDE 3

potential energy

• energy something has based on its position

• comes from concentration gradients and bonds

kinetic energy

• energy something has because of its motion

• comes from constant motion of molecules

open system

biological systmes that exchange matter and energy with surroundings

reactants/substates

starting molecule with certain amount of potential energy

products

results of a reaction could be at a higher or lower energy than reactants/substates

conservation of energy

energy is neither created nor destroyed and can be transferred/transformed

gibbs free energy

measure of usable energy in a biological system

• ΔG: assesses favorability of a reaction  

• ΔH: Enthalpy- heat released or used in reaction 

• ΔS: Entropy- level of energy disorder in a system

• T: temperature measured in Kelvins

gibbs free energy equation

spontaneous reaction

• reactions that do not require external energy

• favorable

• reactants have more free energy than products so ΔG is -

non-spontaneous reaction

• reactions that require external energy 

• unfavorable

• reactants have less free energy than products so ΔG is +

endergonic reactions

reaction that requires energy

ex. dehydration synthesis

• non-spontaneous and there is a positive change in G

excergonic reaction

reaction that releases energy

ex. ATP hydrolysis

• spontaneous and there is a negative change in G

endothermic reactions

reaction that absorbs heat

this is what the change in H is

ex. ice melting

exothermic reactions

reaction that releases heat

this is what the change in H is

ex. wood burning

catabolic reactions

breaking down

• exergonic

involves the overall release of energy

spontaneous negative delta G

anabolic reactions

building up

• endergonic

involves an addition of energy to get the reaction going

non-spontaneous, positive delta G

ATP

• a nucleotide called adenine triphosphate

• cellular “energy currency” because the bonds between the three negative phosphates have high potential energy

• can directly energize proteins in primary active transport

• can energize cellular processes through reaction coupling

reaction coupling

• reaction coupling pairs multiple reactions so non spontaneous reactions can occur

• non spontaneous reaction + spontaneous reaction —> spontaneous pathway: if delta G is negative

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ATP hydrolysis

• spontaneous reaction that breaks off phosphate group from ATP

• has a negative delta G (releases free energy)

• often coupled with non-spontaneous reactions to make cellular processes spontaneous

enzymes

speed up or catalyzes biological reactions by decreasing activation energy

NO IMPACT ON GIBBS FREE ENERGY

activation energy

initial input of energy required to get an

enzyme: substrate

the reactant that interacts with an enzyme

enzyme: cofactor

a non-protein, non-substrate molecule that helps enzyme activity

enzyme: active site

the place on an enzyme where the substrate binds

enzyme: allosteric site

the place on an enzyme where a molecule (not the substrate) binds to inhibit or stimulate enzyme activity

enzymes denaturation

• if enzyme structure is altered, enzyme function will be altered too

• anything that changes protein structure has a potential to either decrease or eliminate enzymatic activity

• ex. pH, temperature, denaturing agents, gene mutations

inhibitors

slow reaction rate

Competitive inhibition

• inhibitor binds at the active site to prevent substrate binding

Non-competitive/allosteric inhibitions

• bind an allosteric site and decrease catalytic activity