Chapter 4- Carbohydrate Structure and Function Flashcards Preview

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Flashcards in Chapter 4- Carbohydrate Structure and Function Deck (37)
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1

monosaccharides

trioses- 3 carbons
tetroses- 4 carbons
pentoses- 5 carbons
hexoses- 6 carbons

2

aldoses

carbohydrates that contain an aldehyde group as their most oxidized functional group

3

ketoses

carbohydrates that contain a ketone group as their most oxidized functional group

4

simplest aldose sugar

glyceraldehyde (aka. aldotriose)

5

which carbon is typically the most oxidized

the carbonyl carbon (attached to the doublebonded O)

6

glycosidic linkages

sugars acting as substituents (typically aldehyde carbon)

7

dihydroxyacetone

simplest ketone sugar (ketose). carbonyl carbon is most oxidized (carbonyl carbon is usually C2)

8

stereoisomers

optical isomers. compounds that have the same chemical formula (only differ from one another in terms of spatial arrangement)

9

enantiomers

same molecular formula
nonsuperimposable
mirror images of each other.

any molecule that contains chiral carbons and no internal planes of symmetry.

10

number of stereoisomers with common backbone

2^n (n = number of chiral carbons in the molecule)

11

fisher projection

horizontal lines (wedges)-- out of page (right side pointing down)
vertical lines (dashed)-- into page

12

diastereomers

same molecular formula
nonsuperimposable
not mirror images

13

epimers

subtype of diastereomers that differ in configuration at exactly one chiral center (ex: D-ribose and D-arabinose)

14

most common electrophile

carbonyl group (C doublebonded to O)

15

pyranose and furanose rings

pyranose- 6C rings
furanose- 5C rings

rings are typically hemiacetals or hemiketals

16

what happens when you expose a hemiacetal ring to water?

they will spontaneously cycle b/w open and closed form

17

mutarotation

interconversion between anomers of a compound (ex: a and B conformations)

spontaneous change of configuration about C-1 and occurs more rapidly when the reaction is catalyzed with an acid or base.

18

reactions that monosaccharides can undergo and why

b/c they contain alcohols and either aldehydes or ketones they can undergo....
1. oxidation/reduction
2. esterfication
3. nucleophilic attack (creating glycosides- sugar bound to another functional group)

19

aldonic acid

the aldehyde group of a monosaccharide is oxidized to a carboxylic acid. this oxidized aldose (reducing agent) is called an aldonic acid.

20

reducing sugars

any monosaccharide with a hemiacetal ring

21

lactone

cyclic ester. when aldose being oxidized is in ring formation then the oxidation yields a lactone. (ex: vitamin C)

22

how to detect the presence of reducing sugars?

Tollen's reagent: uses Ag(NH3)2+ as oxidizing agent. so aldehydes reduce Ag+ to metallic silver
Benedict's reagent: aldehyde group of an aldose is readily oxidized by Cu(OH)2, indicated by a red precipitate of Cu2O

*note: ketose sugars are also reducing sugars and give positive test results for these.

23

Tautomerization

rearrangement of bonds in a compound, usually by moving a hydrogen and forming a double bond.

24

enol

compound with a double bond and an alcohol group

25

alditol

formed when the aldehyde group of an aldose is reduced to an alcohol

26

deoxy sugar

contains a hydrogen that replaces a hydroxyl group on the sugar (most well known is the deoxyribose which is the carbohydrate found in DNA)

27

esterfication

carbohydrates have hydroxyl groups which can react with carboxylic acids and their derivatives to form esters. (most important reaction in body is the phosphorylation of glucose to form a phosphate ester, this uses hexokinase or glucokinase as an enzyme)

28

acetals/ ketals

formed when hemiacetals (hemiketals) react with alcohols under acidic conditions, resulting C-O bonds are called glycosidic bonds and the acetals (ketals) formed are glycosides --dehydration reaction

29

furanosides and pyranosides

glycosides derived from furanose and pyranose rings, respectively -- dehydration reaction

30

esterfication vs. glycoside formation

esterfication- reaction by which a hydroxyl group reacts with either a carboxylic acid or a derivative to form an ester
glycoside formation- reaction b/w alcohol and hemiacetal (or hemiketal) group on a sugar to yield an alkoxy group.