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- (G): The energy released that is able to do work
- Delta G 0' : change in free energy @ standard conditions
- Exergonic - releasing free energy
- ex- conserved ATP
- Endergonic - requiring energy
Calculating Delta G0
- Delta G0' = Gf0 [C+D] - Gf0 [A+B]
- product - reactant
Delta G0' vs Delta G
' : standard conditions
- Delta G : under various conditions
- ( Delta G = Delta G0' + RT ln K )
Energy required for a reacion to occur
- A substance that lowers the activation energy
- --> increasing the rate of rxn
- ex- enzymes
- Biological catalysts
- made of protein
- Enzyme binds to a substrate
- @ the Activation site
- Increase the rate of rxn by 108-20
For enzymes to catalyze a specific rxn...
- 1. bind to the substrate
- 2. position the substrate
- small nonprotein molecules that aid in the catalysis.
- Prosthetic Group - tightly bound to enzyme
- ex- the heme group in Cytochrome
- Coenzyme - loosely bound to enzyme
- ex- derivative of niacin vitamin (NAD+/ NADH)
Oxidation-Reduction rxn require e- donors & e- acceptors. The tendency of a compound to accept or release e- is expressed quantitatively by its reduction potential ( E0' ).
- Energy is conserved in cells from Redox rxn
- ex- ATP
Oxidation vs Reduction
- Oxidation - the removal of an e-: e- donor ex- H2
- Reduction = the addition of an e- : e- acceptor
- ex- O2
for every substance that is oxidized, one must go through reduction.
e- cant be by itself. so only half of the rxn can occur
- potential to accept or donate an e-.
- The more (+) V --> the more able to accept
- The more (-) V --> more donateable
They are expressed in half rxn.
ex: 2 H+
- H2 is more of a donor
- O2 is more of an acceptor
- listing of e- transfer rxn
- strongest reductant on top: (-) e -donors
- strongest oxidant on bottom: (+) e-acceptors
The transfer of electrons from donor to acceptor in a cell typically involve electron carriers.
Some electron carriers are membrane-bound, whereas others, such as NAD+ / NADH, are freely diffusible coenzymes
intermediates between Redox rxn
- Two types:
- 1. Coenzyme - freely diffusible (ex-NAD, NADP)
- 2. prosthetic group -tightly bound within cytoplasmic membrane
Common diffusible carriers within a redox rxn
- Freely diffusible carriers w/ 2e- and 2H+
- 1.NAD + : (nicotinamide-adenine dinulceotide)
2. NADP +
: (NAD + phosphate)
NAD/ NADH Cycling
NAD+ can be reduced to NADH then give away e-, making it NAD+ again
The erngy released in redox rxns is conserved in the formation of compounds that contatin energy-rich phosphate or sulfur bonds.
The most common of these compounds is ATP, the prime energy carrier in the cell. Longer-term stroage of energy is linked to the formation of polymers, which can be consumed to yield ATP
ribonucleoside adenosime + 3 phosphate
- release 32kJ of energy per breakdown
- ATP --> ADP + Pi --> AMP
- energy-rich compounds
- ex - Acetyl CoA
Long term energy storage
ATP is continuously broken down to drive anabolic rxn, and resynthesize at the expense of catabolc rxn.
- Storage: insoluble polymers --> oxidized -->ATP
- EX - glycogen, 'polys' , sulfur (prokaryotes)
- starches and lipids (eukaryotes)
Fermentation and respiration are two means by which chemoorganotrophs can conserve energy from the oxidation of organic compounds.
During these catabolic rxns, ATP is synthesized by either substrate-lvl phosphorylation(fermentation) or oxidatiive phosphorylation (respiration).
produces ATP in fermentation
**Does NOT rely on proton motive force**
produces ATP in respiration
**rely on proton motive force**
productionof ATP in phototrophs
**rely on proton motive force**
Glycolysis is a major pathway of fermentation and is widespread means of anaerobic metabolism.
The end result of glycolysis is th release of a small amount of energy (2ATP) and production of fermented products.
fermentation of glucose (Glycolysis)
3 stages of Glycolysis
- 1. prepartory reaction
- 2. the production of NADH, ATP, and pyruvate
- 3. consumption of NADH and the production of fermented products
ALWAYS: NADH is reoxidized to NAD+
- yeast: pyruvate is reduced by NADH to ethanol, production of CO2
- Lactic acid bacteria: pyruvate reduced by NADH to lactate
distillers, the brewers, and the cheese makers
Electron transport Systems consist of a series of membrane-associated electron carriers taht funtion in an integrated fashion to carry e- from the donor to the terminal acceptor.
Oxidation using O2 as the terminal electron accpetor. very high yield of ATP produced.
Text book focus on Aerobic Respiration
- 1. the way e- are transferred from organic compounds to the terminal e- acceptor
- 2. the way organic carbon is converted to CO2
Electron Transport Carrier Funtions
- 1. mediates the transfer of e- from primary donor to terminal acceptors
- 2. conserve some energy to later make ATP
Types of oxidation-reduction enzymes as part of the ETS
- NADH dehydrogenases
- iron-sulfur proteins
protein bound inside the surface of the cytoplasmic membrane
binds NADH --> NAD+ --> 2e- + 2H+ move on.
- the next carrier of the 2e & 2H
- (keeps the 2H and passes on the 2e)
- contains riboflavin
- bound protein (prosthetic group)
- FMN & FAD
- contain heme prothetic groups
- loses or gains e- through the Iron
- different classes: a, b, c,
- clustesr of iron and sulfur atoms
- ex- ferredoxin
- reduction potential varies
- carry electrons only
- non proteins
- in bacteria, they are related Vitamin K
- Accept 2 e- and 2 H+ but transfer only e-
When e- are transported through an ETC, protons are extruded to the outside of the membrane forming the proton motive force.
Key electron carriers include: flavins, quinones, cytochrome, etc (depends on the organism)
**The cell uses the proton motive force to make ATP throught he activity of ATPsase
Proton Motive Force
- pH gradient and electrochemical potential
- causing the membrane to be energized.-->ATP or just do work
- inside the membrane more negative and alkaline
- ouside the membrane more positive and acidic
Electron Transport Rxn that lead to the formation of the proton motive force
Complexes I & II
- the complex that converst the proton motive force into ATP
- consists of 2 components:
- (1.) a multiprotein extramembrane complex called F1
- (2) a proton-conducting intramembrane channel called F0
Inhibitors and uncouplers
- chemicals that affect the electron flow or the proton motive force.
- inhibitors: CO ad CN stops ETC
- uncoupling: lipid-soluble substances dinitrophenol and dicumarol - makes things leaky
Reversiblity of the ATPase
reason why fermetnative organisms dont have ETC and cant do oxidative phosphorylation
instead function: generate the proton motive force
Respiration results in the complete oxidation of an organic compound with much greater energy than occurs during fermentation.
The citric acid cycle plays a major role in the respiration of organic compounds
Respiration of Glucose
glucose to pyruvate the same in glycolysis
no fermentation but pyruvate is oxidized to CO2 (citric acid cyle)
Pyruvate --> acetyl CoA-->kreb's cycle