Flashcards in Chapter 7 Definitions/Concepts Deck (45)
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Carbohydrates
Structural and protective unit of cell walls of bacteria and plants, connective tissue of animals, and participate in recognition and adhesion between cells. Can be covalently attached to proteins or lipids.
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Polysaccharide
20 or more monosaccharide units.
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Monosaccharide Characteristics
Soluble in water, taste sweet and form colorless crystalline structures. Contain an unbranched carbon chain that can be an open-chain or closed-cyclic.
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Closed-cyclic bond
Carbon of the carbonyl forming a bond with one of the hydroxyl oxygens.
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Aldose
Carbonyl group is found at the end of the unbranched carbon chain forming an aldehyde.
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Ketose
Carbonyl found at any position other then the end, forming a ketone.
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Monosaccharide Composition
Composed of at least three carbons. They all contain one or more asymmetric carbon except ketotriose.
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Monosaccharide Stereoisomers
Determined by the hydroxyl group on the chiral carbon furthest away from the carbonyl. The D form is more common for carbohydrates.
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L Stereoisomers
Are not as common among carbohydrates. Act more like fiber because in humans there is not was to facilitate transfer into cells.
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D-Ketoses
Four and five carbon ketoses are named inserting a "-ul" into the name of the corresponding aldose. All carbonyls are on the 2 carbon.
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Cyclic Monosaccharides
Aldotetroses and all monosaccharides with five or more carbons occur predominately as cyclic structures. Through aldolcondensation they form either a hemiacetal or hemiketal resulting in an additional chiral carbon.
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Chiral Carbon Transformation Through Aldolcondensation
When a hemiketal or hemiacetal is formed it forms an additional chiral carbon that can be either alpha or beta. Alpha if the hydroxyl is pointing down and beta if it is pointing up.
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Pyranoses
Six membered ring structure, can be formed by aldoses as well. Exists in two chair conformations. Boat conformation is not usually seen because of bulky substituents.
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Furanoses
Aldohexoses form a furanose. A five membered ring. Not as stable as the pyranoses.
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Monosaccharide Reducing Agents
Monosaccharides with a carbonyl carbon are capable of reducing other species at the same time as they are being oxidized.
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Non-Reducing Sugars
Some disaccharides that form linkages at the anomeric carbon to prevent the interconversion to the linear form.
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Glycosidic Bonds
Formed between the anomeric carbon and another atom from another molecule. In disaccharides the anomeric carbon is usually linked to an O from another sugar.
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Polysaccharides
Can be homo or heater. Form linear branched chains. Don't have a definite molecular weight because there is no specific stoping signal to end synthesis.
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Homopolysaccharides As Fuel Stores
Starch- fuel storage in plants, found in granules.
Glycogen- fuel storage in animals, found in granules in liver and muscle.
Dextrans -fuel storage in bacteria and yeast..
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Strach
Two types, amylose and amylopectin.
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Amylose
Long and unbranched, D-glucose connected by alpha 1-4 linkages
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Amylopectin
Long and branched, D-glucose connected by alpha 1-4 linkages and alpha 1-6 linkages at branch points.
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Dextrans
D-glucose chains connected by alpha 1-6 linkages and all have alpha 1-3 branches. Some also have alpha 1-2 or 1-4 branches.
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Glycogen
More highly branched then amylopectin. When used one monosaccharide is removed from one of the branched non-reducing ends.
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Homopolysaccharides As Structural Components
Cellulose and Chitin
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Cellulose
Found in plant cell walls. Linear unbranched structures with beta 1-4 linkages. No enzyme to break bond, can't be used as fuel source.
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Chitin
Found in exoskeletons from anthropoids composed of beta 1-4 linkages but no with D-glucose.
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Polysaccharide Sterics
Free rotation around the glycosidic bonds hindered by hydroxyl groups. Hydrogen bonding on the hydroxyl groups direct the 3D structure.
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Starch Structure
The most stable conformation of amylose is a tight helix stabilized by hydrogen bonds. Has 60 degree angles creating a left-handed helix with 6 residues per turn.
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