MCB 2000 Lecture Notes - Lecture 28: Anomer, Monosaccharide, Polysaccharide
16 May 2018
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Lecture 28
Anabolic Pathways
(Creation of more complex molecules from simpler)
Outline
● Why and how do we store energy in body?
○ Glycogen & triglycerides are stored energy reserves that can be tapped into during times
of high demand or need
Storing energy as polysaccharide (Glycogen)
● Animals: glucose stored as glycogen
● Glycogen has fraction of osmotic pressure that would occur with an equiv number of glucose
molecules (polysaccharide is more beneficial than the separate units by themselves)
● Stored in:
○ Liver: 70 grams (10% mass of liver)
○ Muscle: 120 grams (1-2% mass of muscles)
Carbohydrates are hydrates of carbon
● Monosaccharides can’t be broken down to simpler sugars with mild conditions
● Disaccharides: sucrose, lactose, maltose
● Oligosaccharides: 4-10 sugar chains
● Polysaccharides: usually polymers of monosaccharides (many linked together)
Carbohydrate Chemistry
● There is a hydroxyl group at C1 in carbohydrates (anomeric C)
○ Is in the ALPHA position when drawn down
○ Is in the BETA position when drawn up
● When a carbohydrate cyclizes into a ring, alpha & beta anomers are possible
● Monosaccharides are able to be joined to each other through the O-glycosidic Bond (anomeric
carbon reacts with oxygen on the hydroxyl group of the next monosaccharide)
○ Bond can be either alpha or beta
Important Polysaccharides
All contain glucose as monosaccharide, differences due to ALPHA or BETA glycosidic linkages &
structure
● Glycogen (animals ) energy storage
○ branched polysaccharide, ALPHA 1,4 bonds within chain; ALPHA 1,6 at branch points
● Cellulose (plants) - BETA 1,4 linkages structural support
● Starch (plants), consists of 2 parts energy storage
○ Amylose- linear polymer of glucose
○ Amylopectin - branched polysaccharide, ALPHA 1,4 bonds within chain; ALPHA 1,6 at
branch points
Structure of Glycogen
● Branched glucose polymer linked by ALPHA 1,4 glycosidic bonds and ALPHA 1,6 glycosidic
bonds (branch points)
○ Branched structure: rapid synthesis and degradation from multiple reducing ends,
increases solubility
Document Summary
Anabolic pathways (creation of more complex molecules from simpler) Glycogen & triglycerides are stored energy reserves that can be tapped into during times of high demand or need. Glycogen has fraction of osmotic pressure that would occur with an equiv number of glucose molecules (polysaccharide is more beneficial than the separate units by themselves) Liver: 70 grams (10% mass of liver) Muscle: 120 grams (1-2% mass of muscles) Monosaccharides can"t be broken down to simpler sugars with mild conditions. Polysaccharides: usually polymers of monosaccharides (many linked together) There is a hydroxyl group at c1 in carbohydrates (anomeric c) Is in the alpha position when drawn down. Is in the beta position when drawn up. When a carbohydrate cyclizes into a ring, alpha & beta anomers are possible. Monosaccharides are able to be joined to each other through the o-glycosidic bond (anomeric carbon reacts with oxygen on the hydroxyl group of the next monosaccharide) Bond can be either alpha or beta.
