When muscles lack oxygen this will start to build up and cause fatigue?

Lactic acid begins to build up during some exercises, such as running and swimming.
Some people don't build up lactic acid nearly as much, such as Dean Karnazes, who once ran 50 miles in 50 days, then ran the 1300 miles back to the start.

The best way to tell its true color is to look at the minerals streak

Lysosomes contain digestive enzymes (lysozyme) and in digestion of different biomolecules like proteins, fats, starch, etc.cleans the cell by destroying damaged organellesprotects cells from certain virus/bacteria by killing them