String theory and the M theory?

[Nick V]

In string theory/M theory, there are two types of strings, open and closed strings. What kind of strings are fermions(electrons, quarks) made out of? Closed or open strings?

 

[jedishrfu]

From the book The Trouble with Physics by Lee Smolin, the ends of open strings can represent charged particles and closed ones can represent the graviton. See page 106.