Oxygen enters the bloodstream through an exchange reaction between oxygen and carbon dioxide. The ONLY role calcium and magnesium plays is the fact that calcium contracts the bronchioles decreasing respiration and magnesium relaxes the bronchioles increasing respiration. Here are some references to help you with understanding how the body really works:

http://www.peopleandpossibilities.com/dr.rakhra-Pulmonary.html

“Magnesium may help to stop acute asthma attacks and have a dilating effect on the bronchial muscles. “

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1572783/

“The contraction of smooth muscle from different tissues depends to a variable extent on Ca²⁺ influx across the plasma membrane. “

Note Ca refers to calcium.

http://bja.oxfordjournals.org/cgi/content/full/90/5/671

“Calcium (Ca) plays an important role in airway hyperreactivity because synthesis of inflammatory mediators and release from mast cells, airway smooth muscle contraction and neuronal conduction are dependent on cytosolic calcium ions (Ca²⁺), which are elevated via either Ca²⁺ channel opening or release from intracellular stores.¹ “

“As described above, the important role of intracellular Ca²⁺ led to speculation that Ca²⁺ entry blockers may be beneficial in the treatment of asthma. “

http://www.practicalasthma.net/pages/science/calcium_magnes_asthm.htm

“The control of smooth muscle contraction is governed by changes in the intracellular concentration of calcium ions. (1) In the presence of calcium, ATPase is activated to hydrolyse ATP and provides an available energy source for muscle contraction.”

“Magnesium is essential in muscle relaxation after contraction. A severe Mg deficiency causes neuromuscular symptoms such as tetany, an extreme and prolonged contraction of the muscles (10) Within the cells of striated and smooth muscles, magnesium is considered a natural calcium antagonist counteracting the adverse effects of excessive intracellular calcium. Excess magnesium blocks calcium entry, while low magnesium levels potentiate the actions of calcium. (11,12) Magnesium also plays a key role in the production of energy which is needed by the chest wall muscles and the diaphragm to perform the work of breathing. In a double blind study, individuals with low magnesium levels had an increase in the power of their respiratory muscles after receiving an intravenous infusion of magnesium. This effect was not seen in healthy individuals with normal magnesium levels. (13)”

“It is generally thought that magnesium depletion leads to respiratory fatigue. (14). Magnesium promotes healthy lung function by acting as a bronchodilator, preventing the bronchial passages from going into spasm. (15, 16) Magnesium deficiency may increase vulnerabilty to allergies by increasing the release of histamine into the bloodstream, increasing allergic reactivity in general. (17) Magnesium has been found to be deficient in many asthmatics during acute attacks (18), though actual Mg levels may have been lower since blood level measurements do not detect subtle tisssue deficiencies (19). Low dietary intake of magnesium is associated with an increased incidence of asthmatic symptoms, wheezing and reduced lung function. (20)

The administration of intravenous magnesium has been shown to be effective in the treatment of bronchial asthma symptoms. (21, 22)”

http://74.125.113.132/search?q=cache:vFTNgq1V-ZEJ:medind.nic.in/iac/t01/i2/iact01i2p107o.pdf

“Calcium ions are closely involved in excitation contraction of smooth muscle and also in secretory process including the release of mast cell inhibitors. Bronchial smooth muscle contracts when concentration of free cytosolic calcium ions increases due to cell membrane

depolarisation14, however, one of the defects in asthmatics is an altered control of calcium influx15.”

“ In a recent study, calcium channel blockers have been shown to reduce

asthmatic symptoms and airway hyperresponsiveness27.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1400645/?page=1

Clinical studies with calcium antagonists in asthma

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1504786/

“The findings suggest that mediator release, which is calcium dependent, may play an important part in exercise-induced asthma, and calcium antagonists may inhibit post-exercise bronchoconstriction by their blocking effect on calcium channels.”

http://chestjournal.chestpubs.org/content/122/2/396.full

“1. Magnesium has been shown to cause bronchial smooth-muscle relaxation in vitro,

⁷ probably by its action as a “physiologic calcium antagonist,”⁸ or by its action on adenyl cyclase activation.⁹ Magnesium has been shown to cause bronchodilation in vivo¹⁰¹¹¹² in children as well as in adults. Yes, magnesium is a bronchodilator.”

http://www.aafp.org/afp/20040201/tips/39.html

“Magnesium Proves a Useful Adjunct in Acute Asthma

Magnesium has bronchodilating properties attributed to its role as a powerful relaxant of smooth muscle. “

As far as acidity and alkalinity goes you are not telling the full story there either. An alkaline reaction is required for the uptake of oxygen by hemoglobin, but the release of that oxygen is acid dependent. If you cannot release the oxygen it does not do you any good. Calcium and magnesium don't play a role in the uptake or release of oxygen from hemoglobin. Try researching the Bohr effect and the Haldane effect.