free radicals and antioxidants

We often watch TV commercials about free radicals and using antioxidants against them.
Aging process and diseases are said to be due to generation of free radicals either endogenous or exogenously.

http://www.healthchecksystems.com/antioxid.htm

umami -- the fifth basic taste

pleasant taste of food , its not bitter, not sour , not sweet , not even salty. A combination of two, three maybe all of them might might give rise to umami. Is there a scientific basis for the relative new sense of taste?

This sense of pleasant savory taste is due to a certain amino acid called glutamate. It has its own taste bud and receptor, that's why it is designated as the 5th primary taste.

How was it discovered?
http://www.umamiinfo.com/what_exactly_is_umami?/

staining - principles and methods

We can't see them. They are colorless and extremely minute. So we stain them to see their morphology and arrangement.

http://www.personal.psu.edu/faculty/k/h/khb4/enve301/301labs/Lab2_Simple_staining.html