Biochemistry

• Carbohydrate formula is set up so that for every carbon, there is one water molecule
• Carbohydrates have a variety of functions, including energy source and storage, being a structural component of cell walls, and informational molecules in cell-cell signaling
• Three major carbohydrate classes are monosaccharides, oligosaccharides, and polysaccharides
• All carbohydrates initially have a carbonyl group, but they can react with something so that these groups may be modified or lost
• Aldoses with 3+ carbons and ketoses with 4+ carbons contain chiral centers
• Ketoses have one less asymmetric center than aldoses with the same number of carbons
• D- and L- configuration refers to the configuration of the asymmetric carbon furthest from the carbonyl group
• Diastereomers have different physical properties from one another
• When aldehydes are attacked by alcohols, hemiacetals form
• When ketones are attacked by alcohols, hemiketals form
• For cyclization formation, the nucleophilic alcohol attacks the electrophilic carbonyl carbon, then the linear carbohydrate forms a ring structure, and the carbonyl carbon is reduced to an alcohol
• cyclization occurs between the highest alcohol and the aldose/ketose
• with Fischer projections, the left side goes up and the right side goes down on rings
• Pyranose rings favor chair conformations
• multiple chair conformations are possible but they require energy for interconversion
• A free anomeric carbon is one that is not involved in bonding
• Modern reducing sugar detection techniques use colorimetric and electrochemical assays
• If the anomeric carbon is unmodified, then the sugar is reducing
• Enzymatic methods are used to quantify reducing sugars such as glucose
• In glycated hemoglobin analysis, the N-terminus of hemoglobin reacts with the anomeric carbon of the sugar
• Two sugar monosaccharides can be joined via a glycocidic bond between two anomeric carbons
• Lactose is a reducing sugar
• sucrose is a nonreducing sugar
• trehalose is a nonreducing sugar
• glycogen is a branched homopolysaccharide of glucose
• Glycogen has branch points with alpha 1-6 linkers every 8-12 residues
• glycogen is the main storage polysaccharide in animals
• starch is a mix of two homopolysaccharides of glucose
• amylose is an unbranched polymer of alpha 1-4 linked residues
• amylopectn is branched like glycogen, but branch points occur less often, with bps every 24-30 residues
• starch is the main storage polysaccharide in plants
• linear polymers with 1-4 ends will always have a reducing (1) end, and a non-reducing (4) end
• Cellulose has beta linkages and amylose has alpha linkages, which is the major differentiation between the two
• chitin is a linear homopolysaccharide of N-acetylglucosamine
• N-acetylglucosamine monomers form beta 1-4 linked chains
• in chitin, the amino group is added first and then followed by the acetyl group
• agar is a branched heteropolysaccharide composed of agarose and agaropectin
• glycosaminogens are conglomerates of proteins and are negatively charged, as well as being an extended hydrated molecule
• heparin is a linear polymer
• heparin sulfate is a heparin-like polysaccharide that attaches to proteins