Carbohydrates
- Created by: farahh24
- Created on: 11-09-18 13:36
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- Carbohydrates
- Glucose
- Hexose monosaccharide - 6 carbons, 12 hydrogens, 6 oxygens
- Structural variations
- Alpha glucose has hydroxyl group below carbon 1
- Beta glucose has hydroxyl group above carbon 1
- Condensation reactions
- Hydroxyl group on carbon-1 of first glucose molecule interacts with the hydroxyl group on carbon-4 of second glucose molecule.
- Two hydroxyl groups form single oxygen with glycosidic bond. Water as waste product.
- For beta glucose, the second glucose molecule must be turned upside down so hydroxyl groups are close enough to interact.
- Beta glucose has hydroxyl group above carbon 1
- For beta glucose, the second glucose molecule must be turned upside down so hydroxyl groups are close enough to interact.
- Two hydroxyl groups form single oxygen with glycosidic bond. Water as waste product.
- Hydroxyl group on carbon-1 of first glucose molecule interacts with the hydroxyl group on carbon-4 of second glucose molecule.
- Other sugars
- Fructose + glucose = sucrose
- Galactose + glucose = lactose
- Ribose - pentose monosaccharide in RNA
- Deoxyribose - pentose monosaccharide in DNA
- Starch
- Amylose
- Alpha glucose molecules with 1-4 glycosidic bonds.
- Twisted into helix - more compact, less soluble than glucose.
- Amylopectin
- Alpha glucose molecules with mostly 1-4 glycosidic bonds with some 1-6 glycosidic bonds.
- 1-6 bonds form branches every ~25 subunits. Compact. Insoluble. Rigid.
- Energy storage molecule for plants
- Amylose
- Glycogen
- More branches than amylopectin, more compact, requires less space to be stored.
- Storage molecule for animals, which are more mobile than plants and require more carbohydrates
- More branches than amylopectin, more compact, requires less space to be stored.
- Cellulose
- Beta glucose molecules (alternate molecules flipped upside down) forming 1-6 glycosidic bonds.
- Straight, no branching or coils. Rigid. Not compact or soluble.
- Make hydrogen bonds with each layer, forming microfibrils.
- Microfibrils form macrofibrils, which form fibres.
- Testing for carbohydrates
- Benedicts test for reducing sugars
- Add equal volume of Benedict's reagent. Heat mixture in water bath for five minutes.
- Benedict's test for non-reducing sugars
- Boiled with hydrochloric acid. Add equal volume of Benedict's reagent. Heat mixture in water bath for five minutes.
- Iodine test
- Add drops of iodine dissolved in potassium iodide solution.
- If starch is present, solution will change from yellow/ brown to purple/ black
- Add drops of iodine dissolved in potassium iodide solution.
- Benedicts test for reducing sugars
- Reducing vs non-reducing sugars
- Reducing: can act as reducing agent
- Non-reducing: do not have hydroxyl group on anomeric carbon and cannot act as reducing agent.
- Lactose is a reducing sugar. Sucrose in a non-reducing sugar.
- Non-reducing: do not have hydroxyl group on anomeric carbon and cannot act as reducing agent.
- Reducing: can act as reducing agent
- Glucose
- No sugars present: blue. Increasing concentration of sugars present: green, yellow, orange, red.
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