Overview Monosaccharides? Oligosaccharides? Polysaccharides Glycoproteins and Proteoglycans
Carbohydrates Are Chiral Molecules D L Glyceraldehyde Typically but not always L – amino acids D - sugars Hence, these molecules have a measurable optical rotation, which depends upon both the monomer residues and their conformation
Next to last carbon determines D or L New carbon is added as C1 Fisher Formulas
A Way to Explore Monosaccharides John Maser at Leeds has developed a “Monosaccharide Browser” the site is mistry/monosaccharide/ mistry/monosaccharide
Epimers Differ by Configuration at One Chiral Center D-glucoseC2 epimerD-mannose C3 epimerD-allose C4 epimerD-galactose C5 epimerL-idose
Sugars Prefer To Be Cyclic
Hemiacetals and Cyclization Group
-D-Glucose In nature, open chain forms are rare. NMR has shown that all 5 coexist with the pyranose forms occurring 99% of the time, furanose about 0.5% each and a trace of open chain and are “anomers and differ in configuration at the new chiral center formed in the cycle
Pyranose Ring Shapes Pyranose rings can form chair and boat conformers 1 C 4 4 C 1
Polysaccharides Polysaccharides consist of sugar residues linked into a polymer. Polysaccharides, unlike proteins or nucleic acids, are not always linear in sequence The most abundant biomolecules in nature-about tons of cellulose are synthesized each year Functions: structural, food storage, cell surfaces, extracellular matrices.
Polysaccharides May Be the Most Diverse Biomolecules From one 6 carbon hexopyranose sugar such as glucose, you can make 11 different disaccharides and 8 of those lead to infinite polymers From one amino acid or nucleotide you can make only a single dimer. -D-Glucose -D-Glucose
Cellulose: Structural polysaccharide from glucose Microfibrils of cellulose Wood cell (fiber) cell walls are made of cellulose + lignin and hemicelluloses Also found in some bacteria, algae, fungi, seed hairs, and animals (tunicates or sea squirts) n ~
Starch: a-D-Glucose polymer found as an energy storage material in foods Amylopectin Amylose Unlike cellulose, starch can be metabolized by humans. Starches provide the bulk of the energy we obtain from grains, potatoes etc.
Extracellular Matrix: Hyaluronic acid A regular copolymer of N-acetyl glucosamine and Glucuronic Acid (as a metal salt)
HA cont Found in: synovial fluid (knee, shoulder ) Vitreous humor (eye- used in reconstructive eye surgery) Skin – small amounts in all connective tissues
Connective Tissues- fibrous proteins, polysaccharides, and proteoglcans
Other Structural Polysaccharides Mannans – some algae Alginic acids – many algae Chitin- insects, crustaceans (shrimp shell), fungi.