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AP Bio Unit 3: Cellular Energetics Cheat Sheet (DRAFT) by

Enzymes and cellular processes (cellular respiration and photosynthesis)

This is a draft cheat sheet. It is a work in progress and is not finished yet.


Enzymes: biological catalysts that facilitate chemical rxns in cells by lowering the activation energy

-Active site that specif­ically interacts with substrate molecules
-Shape and charge of the substrate must be compatible with the active site of
the enzyme

Enviro­nmental Impacts:
Denatu­ration: protein structure is disrupted, elimin­ating the ability to catalyze rxns
-Envir­onm­ental temper­atures and pH outside the optimal range will cause structural changes
a. pH change can alter H-bonds that provide enzyme structure
b. H temp increases speed of molecules in a solution, increasing frequency of collisions between enzymes and substrates (increase rate of rxn)
-Relative concen­tra­tions of substrates and products determine how efficient rxn is

-Compe­titive inhibitor molecules can bind reversibly or irreve­rsibly to the active site of enzyme
-Nonco­mpe­titive inhibitors can bind allosteric sites, changing the activity of the enzyme

Endergonic vs. Exergonic



1st Law
Nrg cannot be created nor destroyed only transf­erred
2nd Law
every nrg transfer increases entropy (S) of universe; process must increase entropy to be sponta­neous
-Energy input must exceed energy loss to maintain order and to power cellular processes
-Cellular processes that release energy may be coupled with cellular processes that require energy
a. Often sequen­tial; product of rxn is reactant for next step
-Loss of order or energy flow results in death
-Living systems require constant nrg input

Cofactor vs. Coenzyme

Inorganic; Cu, Zn, Mg, Fe, Ca ions; Remove electrons, protons or chemical groups from substrate
Organic (non-p­rot­ein); NAD+, FAD+, vitamin complexes; Remove electrons from substrate and transfer to other molecules
Both aid in proper functi­oning of enzyme


-Variation at the molecular level provides organisms with ability to respond to various enviro­nmental stimuli
-Variation in the number and types of molecules within cells provide organisms with greater ability to survive and/or reproduce in different enviro­nments

Cellular Respir­ation