Chapter 12 - Energetics and Redox Reactions Flashcards
Metabolism
The sum of chemical reactions that occur within a cell.
Catabolism
breakdown of organic and inorganic molecules, used to release energy and derive molecules that could be used for reactions.
Anabolism
synthesis of more complex molecules from simpler organic and inorganic molecules, requires energy
Free Energy (G)
Energy available to do work
Three types of work?
Chemical work (anabolism), transport work (nutrient uptake, and mechanical work (rotation of the flagellum)
Change in free energy?
ΔG°’ - notation - which is the change in free energy under standard conditions
Positive ΔG°’
indicates that the reaction requires energy - endergonic
Negative ΔG°’
indicates that the reaction releases energy - exergonic - releases energy that can be conserved by the cell to do work
Adenosine triphosphate (ATP)
high-energy molecule used by cells for energy currency, donates phosphoryl group to other molecules.
What happens to ATP in exergonic reactions?
As the energy is released, the synthesis of ATP is driven from the addition of a phosphate molecule to adenosine diphosphate, or ADP
Orthophosphate
Pi
What happens to ATP in an endergonic reaction?
Requires energy and will couple the hydrolysis of ATP to ADP + Pi, using the released energy to drive the reaction.
Activation Energy
Energy required to break bonds
Catalyst
substance which assist the reaction to proceed without being changed themselves by the reaction
enzymes
a catalyst used by cells
Oxidation-Reduction reactions (Redox Reactions)
An electron is passed from an electron donor to an electron acceptor, as a way to conserve energy by coupling its synthesis to the release of energy
Oxidation
Loss of its electrons
Reduction
Gain of electrons
Molecule being oxydized
This is the electron donor
Molecule being reduced
This is the electron acceptor
Energy Rich
Molecule with a lot of electrons to donate
Conjugate Redox Pair
The acceptor and donor of a half reaction - every redox reaction consists of two half reactions - 1 donates (oxidized) and 1 accepts (reduced)
Whats on the left of the the couple?
The oxidized form (acceptor)
What is on the right of the couple?
The reduced form (donor)
Name the donor and acceptor: O2/H2O
O2 is the acceptor, H2O is the donor
Reduction Potential
E’o, (Volts) - measurement of the tendency of the donor in the reaction to give up electrons
More Negative E’o
Greater tendency to donate electrons - very good electron donors in reduced form
Less Negative or Positive E’o
Weak Tendency to donate electrons
Redox Tower
lists redox couples in a vertical form based on E’o. Most negative go to top, most positive towards bottom. The reduced substance with greatest tendency to donate would be found at the top right. Oxidized substance w/ greatest tendency to accept on bottom left.
ΔE’o
acceptor E’o minus donor E’o
Larger ΔE’o
More potential Energy for the cell - larger vales are when there is a bigger difference
Actual Formula to proportional ΔE’o and ΔG’
ΔG’=-nF (x) ΔE’o n= number of electrons, F is faraday constant
Electron Carriers
Cellular intermediates that participate in the transference of electrons, with the possibility for energy capture occurring along the way. Go back and forth between reduced (carrying electron) and oxidized (after they passed electron on) forms.
Organization of Electron Carriers
Must be arranged in order of their standard reduction potential. (Down Redox tower), with an electron passed from a carrier with the most negative E’o to a less negative E’o.
NAD+/NADH
Nicotinamide adenine dinucleotide - a coenzyme that carriers both electrons and protons, two of each.
NADP+/NADPH
Dinucleotide phosphate, closely related to NAD+, but accepts 2 electrons and only 1 proton.
FAD/FADH and FMN/FMNH
Flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) - carry two electrons and 2 protons each.
Flavoprotein
Proteins with FAD/FMN
Coenzyme Q (CoQ/Uiquinone
2 electrons 2 protons
Cytochromes
use iron atoms as part of a heme group, carry 1 electron
Iron-Sulfur (Fe-S) protein
such as ferredoxin, use iron atoms not part of the heme group to carry 1 electron at a time
Electron Transport Chain (ETC)
Starts with initial electron donor (substance from outside cell) and ends with final electron acceptor (another substance outside cell)
Middle of ETC
electrons are passed from carrier to carrier as electrons move down tower
Where are ETC’s located?
found within cell membranes of both bacteria and archaea, and mitochondrial membranes of eukaryotes
