Carbohydrates
Made of carbon,hydrogen & oxygen
- Molecule that is an aldehyde or ketone and that has more than one hydroxyl group
- all are chiral
- a class of polyhydroxy aldehydes or polyhyroxy ketones
Monosaccharide & polymers
A carbohydrate w/ 3-7 carbon atoms
Simple sugar
- Disaccharide= 2 units
- Oligosaccaharide = 3-10 units
- Polysaccharide= up to several thousand
Rotation of polarized light
Chiral molecule
- Clockwise: (+) =dextrorotatory
- Counterclockwise:(-) =levorotatory
- measured by polarimeter
Enantiomers often called:
Optical isomers
Equal mixtures of both enantiomers are called:
Racemic mixtures (+)
Diastereomers:
Partly mirror image isomers
Epimers
Special class of diastereomer where the groups around one chiral carbon is reversed
D sugars
- Right side
- Down
L sugars
- Left side
- Up
Anomeric carbon
Cyclic monosaccharides have a new chiral carbon
- “carbon with 2 oxygen molecules attached”
Important monosaccharides:
- D-glucose
- Dextrose
- D-fructose
- D-galactose
- D-ribose
Oxidation
- Primary alcohol⇒aldehyde⇒carb.acid
>oxidation of a monosaccharides produces a sugar acid (most important: glucuronic acid)
Glycoside formation
An alcohol group from one w/the H from another glucose combines to form an ether
Usually the anomeric carbon (greatly increases stability)
- Dehydration (removing H2O)
- Forming an ether
Phosphate ethers
Adding phosphate to monosaccharides(@ the end) as an ester by reaction w/alcohol group
- adds a negative charge
- increase water solubility & chemical reactivity
- important for metabloism
Lactose
Milk sugar
ß-1,4
Sucrose
Table sugar
1-2 link
Maltose
Malt sugar
à-1,4
Amino sugar
One alcohol group (-OH) is replaced by an amino group (-NH2)
- positive charge
*Glucose>glucosamine *Galactose >galactosamine
- N-acetylglucosamine
- N-acetylgalactosamine
Blood type
- Type O: core trisaccharide
- Type A: core + N-acetylgalactosamine
- Type B: core + N-galactose
- Type AB: core + mixture of A & B markers
Chitin
Linear polymer of N-acetylglucosamine
- made in fungi & insects
- highly antigenic, stimulates rapid immune response
Heparin
- Blood anticoagulants
- composed of sugar and amino acids
Glycoproteins
A combination of carbohydrates plus proteins that are present on cells surface.
- function as receptors for molecular messengers or drugs
Cellulose
Fibrous polysaccharide
- connected by -1,4 bonds
- wood, plants,cotton
- insoluble
- indigestible
Starch
Polymer of glucose
- glucose connected by a-1,4 bonds
- produced by plants
- major human food source
