show the linkages between a trisaccharide with the sequence glca–glca–glca. the trisaccharide has an α1→4 glycosidic linkage between the first and second \glca monosaccharides. the trisaccharide has a β1→4 glycosidic linkage between the second and third glca monosaccharides. show stereochemistry using wedge (upward) or dash (downward) bonds.