BIOL 112 Lecture 3: BIOL 112 Sugars and Lipids
16 May 2018
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BIOL 112- Lecture 4- Sugars and Lipids
Carbohydrates :
Cell wall (dark green)
Starch molecules (purple)
1.!Monosaccharides
2.!Disaccharides (2 monosaccharides)
3.!Polysaccharides (many monosaccharides)
The general formula for a carbohydrate monomer is multiples of CH2O. They contain as
many oxygen molecules as carbon molecules.
Ex: C6H12O6 (glucose)
In every molecule, only 1 carbon atoms contain carbonyl oxygen (C=O)
** Note:
Carbonyl (COH)
Carboxyl (COOH)
Hydroxyl (OH)- found in alcohols
Aldose vs Ketose: differ based on where the carbonyl group is found in the chain
Isomers:
In structural isomers, a group is attached to different carbon atoms
Ex: CH3-CHOH-CH3 vs CH3-CH2-CH2OH
In optical isomers/stereoisomers, a group is attach in different ways to
the same carbon atoms. They are mirror images of each other and are
non-superimposable.
Optical isomers can only occur when a carbon has 4 different groups attached to it
Sugar may vary in the configuration of their hydroxyl groups
Ex: glucose vs galactose (these are 2 isomers of the same molecules). The
difference occurs on C4.
In glucose,
-!C1 cannot have an isomer (only has 3 groups)
-!C2 can (4 different groups)
-!C3 can (4 different groups)
-!C4 can (4 different groups)
-!C5 can (4 different groups)
-!C6 cannot (has 4 groups but 2 are the exact same)
Glucose has 24 (16 stereoisomers) isomers possible
When in water, the carbonyl and a
hydroxyl group form a ring form in
water by forming a glycosidic
linkage (which is a covalent bond
between 2 monosaccharides)
-!C1 is now asymmetrical and can
have an additional 2 isomers
(alpha and beta glucose hydroxyl
group either points up or down)
Two glucose molecules can form 11 different
disaccharides, but the only important ones are
the beta1-4 and alpha1-4 linkages because
enzymes have evolved to catalyse these
reactions
-!In this case, the third sugar that attaches
to the C1 of the second can be alpha or
beta
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BIOL 112 Full Course Notes
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Document Summary
The general formula for a carbohydrate monomer is multiples of ch2o. They contain as many oxygen molecules as carbon molecules. In every molecule, only 1 carbon atoms contain carbonyl oxygen (c=o) Aldose vs ketose: differ based on where the carbonyl group is found in the chain. In structural isomers, a group is attached to different carbon atoms. In optical isomers/stereoisomers, a group is attach in different ways to the same carbon atoms. They are mirror images of each other and are non-superimposable. Optical isomers can only occur when a carbon has 4 different groups attached to it. Sugar may vary in the configuration of their hydroxyl groups difference occurs on c4. Ex: glucose vs galactose (these are 2 isomers of the same molecules). C1 cannot have an isomer (only has 3 groups) C6 cannot (has 4 groups but 2 are the exact same)
