NAD+ is used by the cell to "pull" electrons off of compounds and to carry them to other locations within the cell, thus they are called electron carriers

The oxidation of, or removal of an electron from, a molecule (whether accompanied with the removal of an accompanying proton or not) results in a change of free energy for that molecule - matter, internal energy, and entropy have all changed in the process.

Each of these two types of molecules is involved in energy transfer that involve different classes of chemical reactions. It's interesting that while one class of carrier delivers electrons (and energy), the other delivers phosphates (and energy), but both include an adenine nucleotide(s).

In this course we will examine two major types of molecular recyclable energy carriers: (1) nicotinamide adenine dinucleotide (NAD+), a close relative nicotinamide adenine dinucleotide phosphate (NADP+), and flavin adenine dinucleotide (FAD2+) and (2) nucleotide mono-, di- and triphosphates, with particular attention paid to adenosine triphosphate (ATP).

Each individual carrier in the pool can exist in one of multiple distinct states: it is either carrying a "load" of energy, a fractional load, or is "empty".

Keep in mind that a positive ΔE0' gives you a negative ΔG

Using the Nerst equation essentially corrects for the  number of electrons per transfer (here n = 2) and puts things into units biologists can use, and copes with the directionality (sign) for us. F has units of kJ*/volt, E has units of (Volts), so we end up with kJ, a unit of energy.

here n is the number of electrons involved in each transfer, and F is a constant that is a positive number

E0' values and to help us predict the direction of electron flow between potential electron donors and acceptors.

Different compounds, based on their structure and atomic composition, have intrinsic and distinct attractions for electrons. This quality is termed reduction potential or E0’ and is a relative quantity (relative by comparison to some “standard” reaction).

By convention we analyze and describe redox reactions with respect to reduction potentials (E0'), a term that quantitatively describes the "ability" of a compound to gain electrons.

If you consider a generic redox reaction and reflect back on the thermodynamic lectures, what factor will determine whether a redox reaction will proceed in a particular direction spontaneously, and what might determine its rate?

Sometimes a redox tower will list compounds in order of decreasing redox potentials (high values on top and low values on the bottom). Our towers do not- we list (reduced vs. oxidized state) molecule pairs with negative values (highly negative E˚') up top and positive ones (highly positive E˚') towards the bottom. Does presenting the data this way change the redox potential of a compound?

The electron tower is a tool that ranks different common half reactions based on how likely they are to donate or accept electrons.

The amount of energy transferred in a redox reaction is associated with the difference between each half reactions' reduction potential, E0

Because oxidation and reduction usually occur together, these pairs of reactions are called oxidation reduction reactions, or redox reactions.

The ETC produces a proton gradient. No ATP is directly generated in this process. However, the proton gradient is then used by the cell (among other things) to run an enzyme called ATP synthase which catalyzes the reaction ADP + Pi --> ATP. This method of ATP production (called oxidative respiration) results in additional- many additional- ATPs being produced.