The major constituents in agar are
Agar, a polysaccharide extract of a marine alga, is uniquely suitable for microbial cultivation because it is resistant to microbial action and becauseit dissolves at 100degC but does not gel until cooled below 45degC; cells can be suspended in the medium at 45degC and the medium quickly cooled to a gel without harming them.Ref: Jawetz, Melnick, & Adelberg's Medical Microbiology; Twenty-Seventh Edition; Chapter 5; Cultivation of Microorganisms
Fats
Aminoacids
Polysaccharides
Polypeptides
general microbiology