Unformatted text preview: 1/30/17 International Genetically Engineered Machines
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Send applications to: [email protected] Lecture 6
An Introduction to Carbohydrates BIOL 225
Prof. Liz Allison
January 30, 2017 1 1/30/17 Carbohydrates: Sugars and Polymers of Sugars
Monosaccharides • Contain only one sugar molecule • General formula: (CH2O)n
• Form polysaccharides via glycosidic linkages Carbohydrates are i mportant building blocks in the synthesis of other molecules Name two very i mportant sugars that you have already encountered in BIOL 225. Many sugars have the same chemical formula but different structures What is the only difference i n structure? 2 1/30/17 Sugars in aqueous solution tend to form ring structures Difference in orientation is important! Learn the structure of glucose and the rest i s (relatively!) simple … differences in bond orientation and functional groups Disaccharides:
Products of condensation reactions Sucrose is cleaved in your saliva by the enzyme sucrase to release glucose and fructose.
How does the structure of fructose differ from glucose? 3 1/30/17 A 20-ounce soda typically contains 15 teaspoons of either sucrose or high-
fructose corn syrup. • Leading source of calories i n the American diet
• Correlated with obesity and diabetes
• Is the sugar in your soda affecting your mind? • The effect of diet on human health is often evaluated using animal models.
• Researchers tested the impact of drinking fructose solutions on memory, using mice trained to find an escape chamber in a maze.
• Fed control chow, or chow supplemented with a fructose solution, or omega-3 fatty acids, or both • After 6 weeks on the diets, tested again on the same maze. Results: Agrawal, R. & F.G. Pinilla (2012) J. Physiology 590: 2485-2499
P<0.01 P<0.05 How might these results i nfluence your diet while studying biology? 4 1/30/17 Carbohydrates also i ndicate cell i dentity Polysaccharides
Energy storage depots and structural scaffolds Starch: principle storage form for sugar in most plants 5 1/30/17 Glycogen
Storage form in higher animals (e.g. liver, muscle) What is the structural difference between starch and glycogen? Carbohydrates also store chemical energy Glucose – universal cellular fuel
C6H12O6 + 6O2 + ADP + Pi→ 6CO2 + 6H20 + ATP (Energy) Carbohydrates store chemical energy
Starch and glycogen are convenient glucose stores Starch Glucose ATP
What are these?
Glycogen Glucose ATP
phosphorylase Carbohydrates also form fibrous structural materials that protect cells 6 1/30/17 Cellulose: fibrous part of plant cell wall Difference between starch the fuel and cellulose the scaffolding – “a simple twist of a link” Ø The β-1,4-glycosidic linkages are difficult to hydrolyze
Ø Very few enzymes have active sites that accommodate their geometry Chitin: major component of arthropod exoskeleton Cell walls of many fungi and algae What is the difference between cellulose and chitin? Peptidoglycan: A structural polysaccharide in cell walls of bacteria Some antibiotics disrupt formation of the peptide-bonded cross-links What are the differences between chitin and peptidoglycan? 7 1/30/17 “These extracellular constructions act as props for the cells;; they provide every sort of visible form that life creates on our planet. Without them, there would be no trees, no flowers, no animals;; nothing but an amorphous covering of oozy slime made of a myriad of naked cells crawling over each other.”
C. de Duve (1984) Recommended readings from the textbook
Chapter 5 8 ...
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