Biological Molecules

• Monosaccharides are simple sugars
• The most abundant monosaccharide in nature is the sugar D-glucose; also known as dextrose
• Oligosaccharides are joined by characteristic linkages called glycosidic bonds.
• Monosaccharides are freely soluble in water but insoluble in nonpolar solvents.
• Glyceraldehyde is an aldotriose
• Dihydroxyacetone is a ketotriose
• Two sugars that differ only in one carbon atom are called epimers
• D-glucose/D-Mannose and D-Glucose/D-Galactose are examples of epimers
• D-Glucose and D-Mannose differ at C-2
• D-Glucose and D-galactose differ at C-4
• 6-membered ring compounds are called pyranoses
• Aldonic and Uronic acids form stable intramolecular esters called lactones.
• Fehling's reaction test for the presence of reducing sugar, which was used to detect/measure elevated glucose levels.
• Disaccharides: maltose, lactose, sucrose
• Disaccharides consists of two monosaccharides joined covalently by an O-glycosidic bond.
• In disaccharides/polysaccharides the end of a chain with a free anomeric carbon is called the reducing end
• Sucrose is a disaccharide of glucose and fructose, that is formed by plants but not animals.
• Sucrose is a nonreducing sugar
• Polysaccharides are also called glycans
• Glycogen has more branching.
• starch contains two types of glucose polymers: amylose and amylopective.
• Amylose consists of long unbranched chains of D-glucose residues connected by a1-4 links.
• Amylopectin is highly branched.
• glycogen is more extensively branched and more compact than starch.
• Large glycogen granules contain the enzymes responsible for synthesis and degradation of glycogen.
• Glycogen has n+1 nonreducing ends, but only one reducing end.
• cellulose is a tough water-insoluble substance found in the cell wall of plants.
• Cellulose is a linear unbranched homopolysaccharide.
• Cellulose has glucose residues in the B configuration
• Amylose has glucose molecules in the a configuration.
• Glycogen and starch are hydrolyzed by a-amylases and glycosidases which break a1-4 glycosidic bonds.
• Why can't animals use cellulose as source of fuel?

  Because they lack an enzyme to hydrolyze the B1-4 linkages.
• The glucose residues in cellulose are linked by B1-4 glycosidic bonds.
• The most stable 3-D structure for the a1-4 linked chains of starch and glycogen is a tightly coiled helix.
• The most stable conformation of cellulose is when it yields a straight extended chain.
• Starch is amylose