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AP Bio Unit 3 - Enzymes, Cell Processes & Feedback Cheat Sheet (DRAFT) by

AP Biology Unit 3 Exam review

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


first law of thermo­dyn­amics
energy cannot be created or destroyed, can only be transf­ormed from one form to another, ATP CAN BE DESTOR­YED­/CR­EATED
(aka law of conser­vation of energy)
second law of thermo­dyn­amics
during energy conver­sions, entropy increases
More organized or built up compounds have more free energy and less entropy (i.e. glucose) and less organized have less free energy and more entropy (i.e. carbon dioxide).
can det how much free energy is available to do work in cell by calcul­ating Gibbs free energy
if energy is released, reaction is exergonic, and triangle G is neg
if energy is absorbed, reaction is enderg­onic, G is positive
EXergonic reactions power ENDergonic ones
a. Organisms use free energy for organi­zation, growth and reprod­uction. Loss of order or free energy flow results in death.
b. More free energy (ex. Food) than needed will be stored for growth (roots, glycogen, fat, etc.).
d. Reactions can be coupled to maintain a system, ex. Photos­ynt­hesis and cell respir­ation
one substance is reduce, another is oxidized


sum of all the chemical reactions that take place in cells
reaction that breaks down molecules
reaction the BUILD UP molecules
met reactions take place in pathways, each of which serves a specific function
multistep pathways controlled by enzymes
enable cells to carry out their chemical activities w remarkable efficiency

enzyme controlled reactions

enzymes do NOT provide energy for a reaction or enable one to occur that wouldn't on its own
enzymes serve as catalytic proteins that speed up reactions by lowering the activation energy
activation energy
amount of energy needed to begin a reaction
enzymes only affect activation energy and activated complex (how much potential energy this needs/is at)
transition state
reactive (unstable) condition of the substance after sufficient energy has been absorbed to initiate the reaction
(is after reaches activated complex)

charac­ter­istics of enzymes

induced fit model
substrate enters the active site and induces enzyme to alter its shape slightly so substrate fits better
lock and key abandoned bc active site must change
enzyme binds to its substr­ate(s) to form enzyme­-su­bstrate complex
enzymes NOT destroyed during a reaction, are reused
named after their substrate, name ends in "­ase­"
ex: sucrase hydrolyzes sucrose
enzymes catalyze reactions in both direct­ions, to put together AND break apart
often require assistance from cofactors (inorg­anic) or coenzymes (vitamins)
efficiency of enzymes affected by temp and pH
body temp too high, enzymes begin to denature and lose their unique confor­mation AND ability to function

inhibition of enzymatic reactions

regulated by contro­lling when and where diff enzymes are active
can be done by switching on and off the genes that code for enzymes or by regulating them once r made
^(comp­etitive or non compet­itive inhibi­tion)

compet­itive inhibition

-some compounds resemble substrate molecules and compete for the same active site on the enzymes

-compe­titive inhibitors reduce amount of product by preven­tin­g/l­imiting the substrate from binding to the enzyme

-can be overcome by increasing the concen of the susbtrate

non compet­itive inhibition


type if allosteric activation
binding of one substrate molecule to one active site of one subunit of the enzyme causes a change in the the ENTIRE molecule
locks all subunits in the active position
amplifies response of an enzyme to its substrates

negative feedback


positive feedback




noncom­pet­itive inhibition

-allos­teric: a change in shape alters their efficiency
-nonco­mpe­titive inhibi­tor­s/a­llo­steric regulators bind to a site distinct and separate from the active site of the enzyme
-causes enzyme to change in shape which inhibits enzyme from catalyzing substrate into product
-active when product is formed (substrate binds)
-inactive when no product is formed (inhibitor attached to allosteric site)
-binding of either activator or inhibitor locks or stabilizes the allosteric enzymes in either the active or inactive form
-feedback inhibition can be used to regulate a lengthy metabolic pathway. the end product of the pathway is the allosteric inhibitor for an enzyme that catalyzes an early step in the pathway


-adenosine is adenine + ribose
-atp is unstable, phosphates are all negatively charged and repel themselves
-when one phosphate group is removed from atp by hydrol­ysis, more stable adp is formed
-change from less stable molecule to more stable ALWAYS releases energy
-provides energy for all cellular acrivites by transf­erring phosphates to another molecules

cellular respit­ation

Makes ATP for cell use; uses glucose and oxygen makes waste products of carbon dioxide and water; occurs in mitoch­ondria; NADH is electron carrier used


(1) occurs in cytoplasm; anaerobic
(2) rearranges the bonds in glucose molecules, releasing free energy to form ATP from ADP through substr­ate­-level phosph­ory­lation resulting in the production of pyruvate.
2 atp + 1 glucose ->2 pyruvate +4atp
(2 net atp)
enzyme that catalyzes third step, PFK is an allosteric enzyme
inhibits glycolysis when cell contains enough atp
if atp is present in large quanti­ties, inhibits PFK by altering confor­mation of that enzyme and stops glycolysis
ex of how cell regulates atp production through allosteric inhibition

mitoch­ondria structure

matrix­-krebs cycle
cristae membrane (inner membra­ne)-etc
outer compar­tment (inter membrane space)­-proton concen builds up

aerobic respir­ation: citric acid (krebs cycle)

(1) occurs in mitoch­ondrial matrix
(3) occurs twice per molecule of pyruvate
(4) Pyruvate is oxidized further and carbon dioxide is released; ATP is synthe­sized from ADP and inorganic phosphate via substr­ate­-level phosph­ory­lation and electrons are captured by coenzymes (NAD+ and FAD).
(5) NADH and FADH2 carry electrons to the electron transport chain.

aerobic respir­ation: electron transport chain

(1) The electron transport chain captures electrons, pumping H+ ions into the inter-­mem­brane space of the mitoch­ondria.
(2) Electrons are accepted by O2 molecule forming H2O
(3) Concen­tration of H+ builds up within inter-­mem­brane space lowering the pH and ions rush through ATP synthase into the mitoch­ondria matrix. Rush of ions “spins” ATP synthase protein, causing ADP and Pi to join forming ATP by oxidative phosph­ory­lation
series of redox reactions
electroneg oxygen pulls electrons through the etc
NADH provides more energy for atp bc delivers elect to higher energy level in the chain
etc consists mostly of cytoch­romes
proteins struct­urally similar to hemoglobin
present in all aerobes
used to trace evolut­ionary relati­onships

oxidative phosph­ory­lation and chemiosis


anaerobic respir­ation: fermen­tation

a. No oxygen; cell only goes through glycolysis followed by fermen­tation
b. Fermen­tation recycles NAD needed to restart glycolysis
e. Fermen­tation does not make ATP but glycolysis does- 2ATP; very ineffi­cient; sufficient for microo­rga­nisms

alcohol fermen­tation

c. alcohol fermen­tation ex. yeast cells- glucose ethyl alcohol + CO2+ NAD+

lactic acid fermen­tation

d. lactic acid fermen­tation ex. muscle cells- glucose lactic acid + NAD+

photos­ynt­hetic pigments

a. Photos­ynt­hetic organisms capture free energy present in sunlight and use water and carbon dioxide to make carbon products and free oxygen.

chloro­plast structure




light reactions


noncyclic photop­hos­pho­ryl­ation


cyclic photop­hos­pho­ryl­ation


calvin cycle // light INdepe­ndent reactions




modifi­cations for dry enviro­nments


cinal link