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AP Biology: Unit 3 Cheat Sheet (DRAFT) by

Cellular Energetics & Enzymes

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

Enzymes

- enzyme: macrom­olecule that acts as a biological catalyst to speed up reactions by lowering E
A

- substrate: molecule that can interact with an enzyme
- active site: spot to specially interact with the substrate
- cofactor: non-pr­otein bound to the active site to allow for the substrate to properly bind
- coenzyme: organic molecule serving as a cofactor
*enzymes are reusable*

Enzyme Lowers Activation Energy

1. Proper Alignment~
active site allows place for reactants (subst­rates) to come together
2. Pulls Reactants~
breaks chemical bonds before reaction
3. More Conducive~
chemic­al/­phy­sical properties better than those in surrou­nding enviro­nment
4. Form Temporary Bonds~
amino acids in active site bond with the substrate molecule
- catalyze either the forward or reverse reaction --- depends on the concen­tration of reacta­nts­/pr­oducts

Enzyme Reaction Graphs

Enzyme Structure

- same as structure of proteins:
primary, secondary, tertiary, & quaternary
- shape denatures at...
1. high temper­ature~
(thermal agitation) bonds disrupted
ideal at:
35-40 degrees
graph:
wide parabola
2. low pH~
(too acidic) hydrogen bonds disrupted
ideal at:
pH 6-8
graph:
steep parabola (log scale)
(3.) substrate concen­tra­tion~
determine rate of collision
ideal at:
below saturation level
graph:
logistic growth (levels off)

Enzyme Activity

- compet­itive inhibi­tors:
enter the active site in place of the substrate
- noncom­pet­itive inhibi­tors:
bind to a location that isn't the active site (allos­teric site), change enzyme shape, & block substrate
- allosteric regula­tion:
binding of a regulatory molecule at a site that affects the function at a different site
 
ex) allosteric deacti­vation & allosteric activation
- feedback inhibi­tion:
end product of metabolic pathway acts as an inhibitor of an enzyme within the pathway

ATP Background

main 3 kinds of work performed:
1. chemical work- start reactions
 
2. transport work- moving substances
 
3. mechanical work- movement of cilia, contract muscles, etc.
ATP synthesis 2 ways:
1. substrate level phosph­ory­lation
 
↳ phosphate group removed from substrate & added to ADP to form ATP
 
2. chemio­smosis (electron transport chain)
 
↳ H+ ions move across membrane moving e- & uses that energy for ATP synthesis
- uncoup­lers:
chemical in liquid membrane that moves H+ across the membrane (blocks ATP synthesis)

Energy

- metabolic pathway:
series of chemical reactions that has a starting molecule and results in a product
- catabolic pathway:
pathway that breaks down complex molecu­les­/po­lymers into simpler molecu­les­/mo­nomers (releases energy)
- anabolic pathway:
pathway that uses simple molecu­les­/mo­nomers to form complex molecu­les­/po­lymers (consumes energy)
- 1st Law of Thermo­dyn­amics~
conser­vation of energy
 
↳ energy can be transf­err­ed/­tra­nsf­ormed, but can't be created or destroyed
2nd Law of Thermo­dyn­amics~
increases entrop­y/d­isorder (heat)
 
↳ usable forms of energy are changed to useless forms

Free Energy

- free energy (∆G):
portion of a system's energy that can perform work
 
↳ must be negative for reaction to be sponta­neous
 
gravit­ational position
solutes in solvent
molecules (size & #)
higher ∆G
high altitude
clustered
large, few
lower ∆G
low altitude
dispersed
small, many
 
define
how ∆G changes
example
exergonic reaction:
sponta­neous reaction with a net release of free energy
- ∆G
cellular respir­ation
endergonic reaction:
nonspo­nta­neous reaction with free energy absorbed
+ ∆G
photos­ynt­hesis

Photos­ynt­hesis Background

equation:
6CO
2
+6H
2
O (+energy) ➜ C
6
H
12
O
6
+6O
2
two processes:
1. light dependent reaction (light reaction)
 
2. light indepe­ndent reaction (dark reaction)
light reaction
dark reaction
- pigments trap light energy to transform into chemical energy
-forms glucose from CO
2
, ATP, & NADPH+
- breaks down H
2
O to release O
2
(2H
2
O ➜ O
2
+4H++4e-)
- light energy stored in bonds of glucose
- produces ATP from ADP
  
- unites H+ with NADPH+
  

Chloro­plast Structure

- light & dark reactions occur in chloro­plasts
- inner membrane organized into structures that photos­ynt­hesis reactions are located
↳ light reactions occur in the thylakoid
↳ dark reactions occur in the stroma

Pigments

pigments absorb certain light wavele­ngths and reflect others
↳blue/v­iolet:
shortest & more energy
↳red:
longest & less energy
- chloro­phyll appears green due to reflecting green and absorbing red/blue
- chloro­phyll has at least 5 forms that vary:
  
Chloro­phyll type~
Found in~
1. Chl. A
all plants & algae
2. Chl B
all plants & green algae
3. Chl. C
brown algae
4. Chl. D
red algae
5. bacter­ioc­hlo­rophyll
some bacteria
- accessory pigments trap light wavele­ngths different from chloro­phyll
(increase the amount of light used)
carote­noids~
phycob­ilin~
↳ carotene & xantho­phylls
↳ in red algae & blue-green bacteria
↳ yellow, brown, orange colors
↳ absorb violet, blue, and green light
 
↳ allow red algae to live deeper than other types
 

Light Dependent Reaction

- scaffolds to reaction center ➜ chloro­phyll molecules ➜ excited element e- (higher energy level) ➜ e- out of photos­ystem II
- H
2
O breakdown only PS II
- 2e- replaces lost e- in PS II
- e- lost by PS I is replaced by e- from PS II
- ETC taking steps to keep releasing energy for H+ to pass through
- products: O
2
, NADPH, & ATP

Light Indepe­ndent Reaction

- RuBP carbox­ylase:*
↳ a.k.a. rubisco
↳ enzyme changes inorganic to organic
↳ 6 diphos­phate (6C) -- split in half -- 12 phosphate (3C)

- ATP equiva­lents:
↳ 18 ATP (total) = 18 (1 each)
↳ 12 NADPH = 36 (3 each)
↳ TOTAL = 54 ATP used

- ADP & NADPH used from light dependent reaction
- products: ADP, NADP, & glucose

Cellular Respir­ation Background

equation:
C
6
H
12
O
6
+6O
2
➜ 6H
2
O+6CO
2
(+energy)
three stages (w/ O
2
):
1. glycolysis
 
(pyruvate proces­sing)
 
2. krebs cycle
 
3. electron transport chain
two stages (w/o O
2
):
1. gylcolysis
 
2. fermen­tation

Glycolysis

* occurs once
* all cells do this
* does NOT require O
2

- location: cytoplasm
- reactants: glucose, 2 ATP, 2 NAD+, & 4 ADP
- products: 2 pyruvic acids, 2 NADH, & 4 ATP (net gain 2)

Pyruvate Processing

* occurs twice (once per pyruvate)
- location: mitoch­ondria
- reactants: pyruvic acid, NAD+, & coenzyme A
- products: CO
2
, NADH, & aceytyl CoA

Krebs Cycle

* occurs twice
* a.k.a. citric acid cycle
- location: mitoch­ondria
**- reactants: pyruvic acid, FAD, NAD+, & ADP
- products: CO
2
, NADH, FADH
2
, & ATP

Electron Transport Chain

* occurs constantly
* a.k.a. oxidative phosph­ory­lation
- e- from NADH & FADH
2
passed along chain = release energy every step
- H+ moves through channel (energy released)
↳ ADP+P ➜ ATP
- e- combine with O = O
2

↳ O
2
+ 2H+ ➜ 2H
2
O
- makes 32 ATP from 1 glucose
- location: inner membrane of mitoch­ondria
- reactants: NADH, FADH
2
, O
2
, & ADP
- products: ATP, H
2
O, NAD, & FAD

Fermen­tation

* NO O
2

* a.k.a. anaerobic cellular respir­ation
* no ATP production
* recycles NAD for glycolysis
- location: cytoplasm
Alcoholic Fermen­tation
- reaction: pyruvic acid+NADH ➜ ethanol+CO
2
+NAD
Lactic Acid Fermen­tation
- reaction: pyruvic acid+NADH ➜ lactic acid +NAD