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23 Cards in this Set
- Front
- Back
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What is the empirical formula of carbohydrates?
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(CH2O)n
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What chemical class do carbohydrates belong to
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polyhydroxylic aldehydes or ketones
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Are carbs hydrophylic?
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Small ones, yes (d/t substituent hydroxyl groups); Large ones less so.
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What are the three functions of carbs?
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1) Immediate fuel (glucose/fructose) 2) Storage (plant starch/glycogen) 3) Structural components (celluclose/chiltin/glycocalyx)
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What are monosaccarides?
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Simple sugars - cannot be broken down any further by hydrolysis
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What chiral orientation are all monosaccarides?
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Right (D).
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What interconverts hexose isomers?
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epimerases
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What is the structure of an aldose?
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A ketone with an aldehyde group (-[C=O]H)
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What is the structure of a ketose?
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A ketone with a ketone group -[C=O]-
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What three forms does glucose exist in?
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1) Linear [open chain] 2) D-glucofuranose 3) D-glucopyranose
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What is a D-glucofuranose?
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A rare hemiacetal formation of monosaccarides
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What is a D-glycopyranose?
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The most common form of glycose in solution - a hemiacetal w/ a 6-member ring, formed by the condensation of the hydroxyl group on C5 w/ the aldehyde group on C1. BEcause the hydroxyl group can end up on either side during formation, alpha and beta anomers are formed. It takes on a chair conformation
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What is the difference b/t the alpha and beta anomers of monosaccarides?
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the alpha anomer's C1 hydroxyl group is axial, while the beta anomer is equatorial
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Describe the alpha monosaccraride
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B/c the bond is axial, the bonds are more flexible and promote the formation of helicies. It is more compact. This formation is less stable. 1/3 at equilibrium. Used in starches, glycogen, etc. In diagrams, appears to be cis.
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Describe the beta monosaccaride.
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This is a more stable form. 2/3 at equilibrium. Takes up more space. The prefered energy source of cells. Used in structures (E.g. cellulose). In diagrams appears to be trans.
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Name four disaccarides
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Sucrose, maltose, lactose, cellobiose.
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What causes lactose intollerance?
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A shortage of lacstase. Lactose is broken down by bacteria -> release of H2 gas.
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Why do some polysaccarides form helicies?
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Internal hydrogen bonding
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Describe starch
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Few a1-6 bonds = less branching. A mix of amylose (unbranched polymer of a-glucose; forms helix d/t bond angles; turns blue w/ iodine; forms colloidal dispersion in H2O; less readily digested than amylopectin) and amylopectin ('lightly branched')
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Describe glycogen
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a-glucose polymer, highly branched (a1->4)
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Describe Cellulose
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branched polymer of b-glucose (b1->4); forms microfibrils; cannot be digested by animals; not very flexible; some microbes can break it down; relatively insoluble (tends to form crystals)
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What are the two phases of cellulose
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Ia (triclinic, in algae and bacteria - identical chains) Ib (monoclinic, higher plants - distinct alternating sheets)
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What affects the digestion of cellulose?
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Cellulose alters the water structuring at its surface
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