In the brain, what keeps atoms (Cl, Na, Ca) charged? Will Ca+ form a diatomic bond?

Question

I was thinking about Alzheimer patients and memory loss. For a neuron to fire in the brain a calcium ion has land in a gateway channel at the base of the axon. The calcium atom must be ionic. A neutral diatomic calcium molecule (I think) wouldn't work.

I've always thought that calcium was a pretty important component of good memory based on the above. (I wonder if a lack of calcium in the brain triggers osteoporosis.)

What I was really thinking about is what is the makeup of the "plaque" that forms around neurons, which is thought to be the cause of alzheimer's. Is the plaque caused by a lack of what ever keeps atoms from forming diatomic bonds? Are normally ionic atoms forming harmful molecules that clump around the neuron?

Answer 1

>>In the brain, what keeps atoms (Cl, Na, Ca) charged?

These are the reactions that would have to occur for the ions to convert to neutral elemental forms, with the reaction potentials in parentheses:

2Cl- --> Cl2 + 2e- (-1.36 volts)
Na+ + e- --> Na (-2.71 volts)
Ca++ + 2e- --> Ca (-2.76 volts)

All are extremely unfavorable (as indicated by the negative potentials). The atoms are more stable--particularly in aqueous solutions--as ions.

>>A neutral diatomic calcium molecule...

Metals, such as calcium and sodium, exist as crystalline lattices in their solid elemental forms. You will never see them as diatomics (unless you vaporize them--but that is something you generally won't see in biology).

>>What I was really thinking about is what is the makeup of the "plaque" that forms around neurons, which is thought to be the cause of alzheimer's.

The plaques are composed of protein. The protein is in the form of amyloid fibrils, which are tough, insoluble aggregates.

Answer 2

I don't know where the plaque comes from, but there is one thing that bothers me about that idea. Two Ca 2+ ions can't form a Ca2 neutral diatomic molecule. The charges have to balance--you have four positive charges to begin with. They either have to find something negative to cancel with, or else there will still be four positive charges at the end.