Agarobiose, the repeating unit of Agarose, is a disaccharide composed of D-galactose and 3,6-anhydro-L-galactose
is the repeating unit of the agarose polymer
Agar is a heteropolysaccharide composed of agarose and agaropectin. Agarose makes up the majority of agar and consists of repeating units of agarobiose, while agaropectin is a minor component with a more complex structure.
It's a differential agar used to differentiate between lactose fermenters and non-lactose fermenteing bacteria. Chemical composition of Mac Conkey agar Peptone 20.0g Trehalose 10.0g Bile salts(Difco) 1.5g Sodium Cloride 5.0 Neutral Red 0.05g Crystal Violet 0.001 Agar 15.0g Distelled water 1.0 liter pH: 7.4±0.2 (25 °C)