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BIO1140 Chapter 3b - The Macromolecules of the Cell (part 2)

BIO1140 Chapter 3b - The Macromolecules of the Cell (part...

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CARBOHYDRATES The monomers are Monosaccharides Polysaccharides are long-chain polymers of sugars and sugar derivatives Consists of a single monomer – monosaccharides Can be an aldehyde (1 hydroxyl group) or a ketone (2 or more hydroxyl groups) o Aldosugars – terminal carbonyl group o Ketosugars – internal carbonyl group Can also be classified by the number of carbons which they have o 3 - triose o 4 - tetrose o 5 - pentose o 6 - hexose o 7 - heptose Most common monosaccharide is an aldohexose – d-glucose o It has 4 asymmetric carbons o Therefore have 16 possible stereoisomers (d-glucose is the most stable) Formula for carbohydrates: C n H 2n O n Put pic in on page 61 See note on page 62 about Haworth projection Disaccharides – consists of two monosaccharide units linked covalently Three common disaccharides are: o Maltose --- alpha D-glucose + alpha D-glucose Alpha glycosidic bond o Lactose --- beta D-glucose + beta D-galactose Beta glycosidic bond o Sucrose --- alpha D-glucose + beta D-fructose Alpha glycosidic bond Alpha – down Beta – up (b’s – up) PUT IN PIC ON PG 62 OF COMMON DISACCHARIDES
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They are all formed by a condensation reaction which results in a glycosidic bond o Bonds can be alpha or beta depending on the configuration of the hydroxyl group of the first carbon atom Polymers are Storage and Structural Polysaccharides Polysaccharides have either a storage or structural function Storage – starch in plants; glycogen in animals Glycogen: o Consist of alpha D-glucose units and alpha glycosidic bonds o There may be alpha bonds that link carbons 1 to 4 of adjacent glucose units o These polysaccharides may contain an occasional alpha linkage (between carbons 1 – 6) along the backbone -- DON’T UNDERSTAND Can be branched depending on presence of these alpha linkage Ex. Glycogen is highly branched because there is an alpha linkage occurring every 8 to 10 glucose units along the backbone. This causes short side chains (8- 12 units long). It is stored in the liver as a source of glucose to maintain blood sugar levels or a fuel source to generate ATP for muscle contraction Starch: o Unbranched – amylose o Branched – amylopectin It as alpha branches (between
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BIO1140 Chapter 3b - The Macromolecules of the Cell (part...

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