Piggybacking: There are also amino acids that are fairly basic (lysine, arginine, histidine); the properties of an amino acid (ie its pH) is largely determined by what’s going on with the amino acid itself (the actual aminal) instead of the C-terminus or N-terminus.

Yes! This is actually how you can pick up on chronic internal bleeding within the digestive tract (along with constitutional systems like black tarry stools/dark stools); it’s called anemia of chronic disease. You see this occur in your inflammatory bowel diseases. On routine labs you can see an anemia and it clues you into a long term inflammatory process if you can rule out diet deficiency or other hematological pathologies.

You can use different gases (see Pepsis new nitrogen based fizzy drink) to infuse a drink. Helium and other gases may not dissolve as well though. You need to induce a good sum of pressure to dissolve the gas into the liquid and the amount of gas dissolved is fairly high to achieve the “carbonated,” effect when you open the beverage. Not all gases will be able to achieve that or the pressure may be so high to keep those gases in the drink a conventional beverage becomes impractical as storage (the actual cans) becomes a larger factor.

Secondly the gas changing your voice; you’d need to be directly inhaling the gas for it to reach your vocal chords and the important vocalization structures in your larynx. Your epiglottis closes off all air/liquid passage to the larynx and lungs when you drink a beverage so the gas would be largely impassable; unless you directly breathed the gas in from the drink (this would still likely not produce enough gas to change your voice; you’re better off just inhaling the gas at this point due to cost and effectiveness).