danceswithtree t1_iwnij6r wrote on November 16, 2022 at 11:11 PM

From what I remember the H+ used in chemical/biochemical reactions is shorthand for a "solvated" proton. Nekkid protons don't really occur under normal conditions. For example, take two H20 molecules. One can donate a proton to the other. The first water then becomes an OH- ion and the latter a H3O+ "solvated" species, i.e. water with an extra proton. This species can then donate a free proton into reactions where you see an H+. See

https://escholarship.org/uc/item/9m11233k#page-1

for an in depth discussion.

Edit: wrong charge.

noiamholmstar t1_iwnkqoj wrote on November 16, 2022 at 11:27 PM

What happens to the hydroxide?

danceswithtree t1_iwnnah8 wrote on November 16, 2022 at 11:47 PM

There are always OH- species in water from the self-ionization of water, i.e. 2H20 <--> H30+ and OH-. This adds a bit more. And this isn't a one way reaction. The reactions that require a proton are balanced out by the reactions that donate protons. Maybe not instant to instant but over the long term.

And you need something the balance out the charges. For example,

NADPH and H+ and acceptor <--> NADP+ and reduced acceptor

You need the OH- to charge balance the NADP+ and the H+. So maybe think

NADPH and H+ (and OH-) and acceptor <-->

NADP+ (and OH-) and reduced acceptor

You can't have loose charges running around all over the place-- that would be mayhem.