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AP Bio Unit 3: Cell Energetics Cheat Sheet by

AP Bio Unit 3: Cell Energetics

Enzymes

proteins (and RNA)
organic catalysts that lower the required activation energy to get reactants to products
facilitate chemical reactions:
~ increase rate of reaction without being consumed
~ reduce activation energy
~ do not change free energy released or required
substrate:
~ reactant which binds to enzyme
~ enzyme­-su­bstrate complex: temporary associ­ation
product:
~ end result of reaction
active site:
~ enzyme's catalytic site: substrate fits into actives site

pH

changes in pH:
~ adds or removes H+
~ disrupts bond, disrupts 3D shape
~ disrupts attrac­tions between charged amino acids
~ affects 2' and 3' structure
~ denatures protein

Activators

cofactors:
coenzymes:
small, inorganic compounds and ions
organic compounds
binds with enzyme
bind to enzymes near active site
Mg, K, Ca, Zn, Fe
vitamins (NAD, FAD, Coenzyme A)

Allosteric Regulation

confor­mat­ional changes by regulatory molecules
inhibi­tors: keeps enzyme in inactive form
activa­tors: keeps enzyme in active form

Metabolic Pathways

catabolic pathways:
metabolic pathways:
release energy
consume energy
cellular respir­ation
photos­ynt­hesis

Transf­orm­ation of Energy

sunlight -> chemical bonds during photos­ynt­hesis

Exergonic vs. Endergonic Reactions

 
exergonic:
enderg­onic:
positive / negative G free energy:
negative
positive
released / absorbed
released
absorbed
cellular respir­ation / photos­ynt­hesis
cellular respir­ation
photos­ynt­hesis
uphill / downhill
downhill
uphill
sponta­neous
sponta­neous
not sponta­neous

Endotherms

regulate internal body temper­atures through metabolism
balancing heat loss and gain
five adapta­tions help animals thermo­reg­ulate:
1) insulation
2) circul­ating adapta­tions
3) cooling by evapor­ative heat loss
4) behavioral responses
5) adjusting metabolic heat production

Overview of Photos­ynt­hesis

Glycolysis

location:
cytoplasm
reactants:
~ glucose
 
~ 2 ADP +2 Pi
 
~ 2 NAD+
products:
~ 2 pyruvate
 
~ 2 ATP
 
~ 2 NADH
 
~ 2 H2O
transfer of energy:
NADH (electrons and Hydrogen) <- C6H12O6 -> ATP
purpose:
~ convert glucose to pyruvate
 
~ initial breakdown of sugar
 
~ generating ATP
 
~ shuttling e- and H+ to ETC

REDOX Reactions

molecular exchange of an electron
oxidation: lose electrons
reduction: gain electrons

REDOX reactions image

Photos­ynt­hesis

transf­orm­ation of solar light energy trapped by chloro­plasts into chemical bond energy stored in sugar and other organic molecules
1) synthe­sizes energy rich molecules
2) uses CO2 as carbon source
3) directly or indirectly supplies energy
CO2 + H2O + sunlight -> C6H12O6 + O2

Steps of Light Reactions

1) H2O splits
~ H+: pump into thylakoid out of ATP synthase
~ e-: 2 ETCs
~ O2: released out of stomata
2) light excites e- in Photos­ystem II
3) e- to primary electron acceptor (PEA)
4) the e- travels down the ETC and replaces the e- from Photos­ystem I
5) the e- travels down another ETC and combines with NAHP+
meanwh­ile...
~ energy from 1st ETC is used to pump H+ into the thylakoid space
~ a proton gradient forms and H+ leave through ATP synthase
~ H+ combines with e- and NADP+ to form NADPH
~ ATP synthase generates ATP
 

Properties of Enzymes

reaction specific:
~ each enzyme works with a specific substrate chemical fit between active site and substrate
~ H bonds and ionic bonds
not consumed in reaction:
~ single enzyme molecule can catalyze thousands or more reactions per second
~ enzymes are unaffected by the reaction
affected by cellular conditions
~ ex: temper­ature, pH, salinity, etc.

Substrate Concen­tration

as substrates increase, reaction rate increases and levels off
more substrate = more frequently collide with enzyme
the reaction levels off because...
~ all enzymes have active site engaged
~ enzyme is saturated
~ maximum rate of reaction

Factors that Affect Enzyme Structure

Compet­itive Inhibitors

inhibitor competes with active site
substrate cannot bond
can overcome with substrate saturation
penicillin (competes with bacterial enzyme that builds cell wall)
directly blocks active site

Energy

the ability to do work
kinetic energy:
potential energy:
energy of motion
energy of position
heat
water behind a dam
light energy
chemical energy stored in cells

Free Energy and Equili­brium

free energy: energy available to do work
free energy decreases when reactions proceed toward equili­brium

Biosyn­thesis

building complex molecules out of simple molecules
amino acids -> proteins
glucose -> glycogen

Ectotherms

do not regulate internal body temper­ature
rely on enviro­nmental heat sources
less respir­ati­on/food

Cellular Respir­ation

catabolic
C6H12O6 + O2 -> CO2 + H2O + energy
steps:
1) gylcolysis
2) interm­ediate step
3) citric acid cycle
4) oxidative phosph­ory­lation

Interm­ediate Step

location:
mitoch­ondrial matrix
reactants:
2 pyruvate
products:
~ acetyl CoA
 
~ 2 NADH
 
~ 2 CO2
transfer of energy:
pyruvate (sugar) -> NADH (e- and H+)
purpose:
convert pyruvate into more reactive Acetyl CoA

Oxidative Phosph­ory­lation

location:
~ inner membrane of mitoch­ondria (ETC)
 
~ inner membrane spare (chemi­osm­osis)
reactants:
~ NADH
 
~ FADH2
 
~ ADP+P
 
~ O2
products:
~ NAD+H
 
~ FAD+H
 
~ ATP
 
~ H2O
transfer of energy:
NADH/FADH2 -> proton gradient -> ATP synthase -> ATP
purpose:
use REDOX reactions to make a large amount of ATP (34)

producers

autotr­ophic nutrit­ional: nutrit­ional made of synthe­sizing organic molecules from inorganic raw materials
photoa­uto­trophs: uses light energy
chemoa­uto­trophs: oxidation of inorganics for energy

Chloro­plast

site of photos­ynt­hesis
double membrane system
thylak­oids: flattened photoc­enters
granum: stacks of thylakoids
stroma: fluid outside thylakoid

Calvin Cycle

location: stomata
production of sugar
recogn­ition of RUBP
reactants: CO2, NADPH, ATP
products: C6H12O6, NADP+, ADP+Pi, G3P

Pathways of Photos­ynt­hesis

noncyclic photop­hos­pho­ryl­ation produces ATP and NADPH
cyclic photop­hos­pho­ryl­ation is ATP production
calvin cycle consumes more ATP than NADPH

C3 vs. C4 vs. CAM plants

 

Induced Fit

"lock and key"
3-D structure of enzyme fits substrate
substrate binding cause enzyme to change shape leading to a tighter fit
"­con­for­mat­ional change­": slight change in shape
bring chemical groups in position to catalyze reactions

Enzyme Concen­tration

as enzymes increase, reaction rate increases
more enzymes = more frequently collide with substrates

Temper­ature

optimum temper­ature:
~ as temp increases, reaction rate increases
~ greater number of molecular collisions
cold temper­ature:
~ molecules move slower
~ decrease collisions between enzymes and substrates
heat (beyond optimum)
~ increased energy level disrupts weak bond in 2' and 3' structure
~ denatu­ration: loses 3D shape

Noncom­pet­itive Inhibitors

inhibitor binds to allosteric site (not active site) which changes the shape of the active site
ex: anti-c­ancer drugs, cyanide, poisoning, DDT

Compet­itive vs. Noncom­pet­itive Inhibitors

Thermo­dyn­amics

study of energy transf­orm­ation
first law: energy of the universe is constant
second law: every process increases the entropy of the universe
entropy: "­qua­ntity of energy in universe is constant, but quality is not"

ATP Powers Cellular Work

coupling enderg­oni­c/e­xer­gonic reactions
energy coupling: phosph­ory­lated interm­edi­ates; regene­ration of ADP to ATP
3 main types of work
1) mechanical work (motor protein)
2) transport work (Na/K pump)
3) chemical work

Size and Metabolic rate

larger mammals have more body mass and require more chemical energy (higher BMR)
smaller animals require more kcal/gram, have greater rate of O2 delivery, higher breathing rate
increase activity -> increase metabolic rate -> more ATP

Overview of Cellular Respir­ation

Citric Acid Cycle

location:
mitoch­ondrial matrix
reactants:
~ acetyl CoA
 
~ citric acid
 
~ ADP + Pi
 
~ NAD+ and FAD
products:
~ oxaloa­cetate
 
~ ATP
 
~ NADH and FADH2
 
~ CO2
transfer of energy:
NADH and FADH2 (e- and H+) <- citric acid -> ATP
purpose:
~ complete the oxidation of glucose
 
~ producing NADH/FADH2 (e- and H+)
 
~ ATP

Phosph­ory­lation

substr­ate­-level: ATP is synthe­sized by enzymes
oxidative: ATP is synthe­sized by an ETC and chemio­smosis

Fermen­tation

anaerobic process (no O2)
produces small amounts of ATP
regene­rates NAD+/NADH
alcoholic fermen­tation
~ yeast/­bac­teria
~ produces CO2 and alcohol
lactic acid
~ human muscles
~ yogurt
~ produces lactic acid

Consumers

hetero­trophs: acquire organics to create energy from other creatures
~ consumers
~ decomp­osers

Light Reactions

occurs in the thylakoid
splitting of water
generation of ATP and NADPH
reactants: H2O, NADP+, ADP+Pi
products: O2, NADPH, ATP

Steps of Calvin Cycle

1) carbon fixation
~ ribulose biphos­phate: RuBP
~ rubisco: RuBP carbox­ylase: most abundant protein
2) reduction
~ adding H+ and e- from NADPH to CO2 to make sugar
3) regene­ration
~ G3P -> RuBP

Altern­ative Pathways of Carbon Fixation

photor­esp­ira­tion: fixing oxygen rather than CO2
C3 plants:
~ hot/dry days
 
~ stomata close (prevents H2O, inc CO2, dec O2)
C4 plants:
~ spatial separation of calvin cycle into bundle sheath cell
 
~ PEP carbox­ylase initially captures CO2
CAM pathways:
~ temporal separation
 
~ takes in CO2 at night

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