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Flashcards

Carbohydrates

Tamika Demiyah CZB190 English 29 cards

Cards in this deck (29)

  1. 1What are carbohydrates?A polyhydroxylaldehyde (aldehyde w/ many -OH groups), polyhydroxylketone (ketone w/ many -OH groups) or compounds that yield these substances after hydrolysis
  2. 2What is the general formula of a carbohydrate?Cn(H2O)m
    where n = carbon atoms; m = no. H2O molecules
  3. 3What is the simplest form of carbohydrate and what is its molecular formula?Monosaccharides - cannot be hydrolysed into anything smaller
    Formula: CnH2nOn (where n = no. atoms & 1 carbon is either an aldehyde or ketone)
  4. 4How are carbohydrates named?Suffix - ose indicates that molecule is carbohydrate
    Prefix (tri-. tetra-, pent-, etc.) indicates no. C atoms in the chain
    Pre-prefix (aldo- or keto- ) indicates aldehyde or ketone
  5. 5RECAP! What is the difference between enantiomers and diastereomers?Enantiomer: stereoisomers whose molecules are non-superimposable images of each other
    Diastereoomer: stereoisomers whose molecules are NOT mirror images
  6. 6True or false. Are carbohydrates chiral molecules?True.
    Central C-atom has 4 different groups attached.
  7. 7How are D- and L- monosaccharides distinguished?D-monosaccharide: -OH on penultimate carbon in Fisher projection is on the right
    L-monosaccharide: -OH on pentultimate carbon in Fisher projection is on the left
  8. 8What are amino sugars?Carbohydrates that contain an -NH2 group in place of an -OH group
    *derivatives of carbohydrates
  9. 9RECAP! What product is formed from the reaction between aldehydes or ketones, and alcohols?Hemiacetals
  10. 10Describe the ACTUAL shape of monosaccharides?5- and 6-membered cyclic HEMIACETALS
    *they have hydroxyl, carbonyl groups, R and OR chain
  11. 11What are anomers?Stereoisomers that differ in configuration only at the anomeric carbon
  12. 12True or false. Pyranose contains 5 carbons and furanose contains 6 carbons.False.
    -pyran describes 6-membered hemiacetals
    -furan describes 5-membered hemiacetals
  13. 13What is mutarotation?~ The change in specific rotation that occurs when the alpha or beta anomers of a carbohydrate are converted to an equilibrium mixture
    ~ occurs in all carbohydrates that exist in hemiacetal forms
  14. 14What is Tollen's test?A test for aldehydes. Aldehydes are readily oxidised to form carboxylic acids whereas ketones are not.
    Formation of metal precipitate indicates presence of aldehyde
  15. 15True or false. Cyclic monosaccharides containing a "hidden" aldehyde undergo the same standard reactions of this functional group.True.
  16. 16Why are monosaccharides that react in Tollen's Test considered 'reducing sugars'?The sugar is oxidised to carboxylic acid and something else (e.g. metal oxidant) is reduced to form metal precipitate
  17. 17Complete the sentence. All monosaccharides with a ___________ group are reducing sugars.Hemiacetal. (from aldehyde + alcohol reaction)
  18. 18What product forms from the reduction of carbohydrates?Alditols
    (similar to reduction of aldehydes which form primary alcohols)
  19. 19What product is formed from the addition of an alcohol to the anomeric carbon of a monosaccharide? (Hint. monosaccharide = cyclic hemiacetal)Cyclic acetal, aka glycoside
    *the bond between the anomeric carbon and new OR group = glycosidic bond
  20. 20How to remember the difference between hemiacetals and acetals.Hemiacetals: 1x -OR group
    Acetals: 2x -OR groups
  21. 21What are 4 main characteristics of glycosides (acetals)?- are stable
    - do not undergo mutarotation
    - are not oxidised by Tollen's reagent
    - therefore, are not reducing sugars
  22. 22What product is formed from the addition of an -NH group to the anomeric carbon of a monosaccharide? (Hint. monosaccharide = cyclic hemiacetal)N-glycosides.
    *Glycosidic bond between anomeric carbon are new -NR group
  23. 23What product is formed from the reaction between monosaccharides and phosphoric acid?Phosphate esters.
    ~ hydroxyl group of monosaccharides react w/ H2PO4 to form phosphate esters
    ~ for glucose, this involves the esterification of hemiacetal group (carbon 1) or primary alcohol group (carbon 6)
  24. 24What are the 3 main types of polysaccharides?Starch
    Glycogen
    Cellulose
  25. 25Briefly explain starch.~ Energy storage in plants
    ~ 2 principle polysaccharides: amylose & amylopectin
  26. 26What is the difference between amylose & amylopectinamylose: unbranched; alpha-1,4-glycosidic bonds
    amylopectin: alpha-1,4-glycosidic bonds + branches created by alpha-1,6-glycosidic bonds
  27. 27Briefly explain glycogen.~ energy storage for animals
    ~ branched polymer of D-glucose joined by alpha-1,4- and alpha-1,6-glycosidic bonds
  28. 28What is the difference between glucogenesis & glycogenolysis?Glucogenesis: conversion of excess glucose to glycogen
    Glycogenesis: conversion of glycogen to glucose (drop in glucose blood level)
  29. 29Briefly explain cellulose.~ plant skeletal polysaccharide
    ~ D-glucose joined by beta-1,4-glycosidic bonds

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CZB190 Flashcards on Carbohydrates , created by Tamika Demiyah on 26/05/2020.
Created by
Tamika Demiyah · May 2020
Updated
Jun 15, 2020
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