Monosaccharides and Disaccharides Flashcards

1
Q

what is the difference between a ketose and an aldose sugar

A

If the carbonyl group is at an end of the carbon chain (that is, in an aldehyde group) the monosaccharide is an aldose; if the carbonyl group is at any other position (in a ketone group) the monosaccharide is a ketose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the two simplest monosaccharides

A

two three-carbon trioses: glyceraldehyde, an aldotriose, and dihydroxyacetone, a ketotriose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the most common monosaccarides in nature

A

The hexoses, which include the aldohexose D-glucose and the ketohexose D-fructose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Monosaccharides Have __________ Centers

A

Asymmetric

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

All the monosaccharides except ____________ contain one or more ____________ carbon atoms and thus occur in __________________

A

dihydroxyacetone
asymmetric (chiral)
optically active isomeric forms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the simplest aldose and describe its structure

A

glyceraldehyde, contains one chiral center (the middle carbon atom) and therefore has two different optical isomers, or enantiomers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the relationship bween chiral center and stereoisomers

A

a molecule with n chiral centers can have 2n stereoisomers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what isomers are most of the hexoses of living organisms

A

D isomers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

When the hydroxyl group on the reference carbon is on the______ in the projection formula, the sugar is the D isomer; when on the _____, it is the L isomer

A

right

left

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the structure of common monosaccharides

A

Cyclic Structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how do aldotetroses and monosaccharides with 5+ carbon atoms form a cyclic structure

A

carbonyl group forms a covalent bond with the oxygen of a hydroxyl group along the chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The formation of ring structures in monosaccahrides is the result of

A

reaction between alcohols and aldehydes or ketones to form derivatives called hemiacetals or hemiketals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are anomers

A

Isomeric forms of monosaccharides that differ only in their configuration about the hemiacetal or hemiketal carbon atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the anomeric carbon

A

hemiacetal (or carbonyl) carbon atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the interconversion of the two cyclic forms of D-glucose called

A

mutarotation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the two cyclic forms of D-glucose

A

alpha D pyranose and beta D pyranose

17
Q

why are the six membered ring compounds referred to as pyranose

A

because the resemble a 6 membered ring compound called pyran

18
Q

what are furanoses

A

Aldohexoses existing in cyclic forms having fivemembered rings

19
Q

which predominates in aldohexose solutions, aldopyranose or aldofuranose ring, and which one is more stable

A

aldopyranose

20
Q

explain the reducing ability of monosaccharides

A

Monosaccharides can be oxidized by relatively mild oxidizing agents such as ferric (Fe+3) or cupric (Cu+2) ion. The carbonyl carbon is oxidized to a carboxyl group

21
Q

what is a sensitive method of measuring blood glucose levels

A

employ an enzyme, glucose oxidase

22
Q

how is a disaccharide formed

A

consist of two monosaccharides joined covalently by an O-glycosidic bond, which is formed when a hydroxyl group of one sugar reacts with the anomeric carbon of the other

23
Q

The oxidation of a sugar’s anomeric carbon by cupric or ferric ion occurs only with the_______ which exists in equilibrium with the____________-

A

linear form

cyclic form

24
Q

how does the disacchraide become a non-reducing sugar

A

When the anomeric carbon is involved in a glycosidic bond, that sugar residue cannot take the linear form and therefore becomes a nonreducing sugar

25
what is the reducing end of a disaccharide or polysaccharide
the end of a chain with a free anomeric carbon (one not involved in a glycosidic bond)
26
what are glycosidic bonds hydrolyed by and also resist cleavage by
acid base so disaccharides can form free mono when boiled with diulte acids
27
what does maltose contain
two D-glucose residues joined by a glycosidic linkage between C-1 (the anomeric carbon) of one glucose residue and C-4 of the other
28
why is maltose a reudcing sugar
Because the disaccharide retains a free anomeric carbon
29
what is the configuration of the anomeric carbon atom in the glycosidic linkage of maltose
α (alpha)
30
what does lactose yield in hydrolysis
D-galactose and D-glucose on hydrolysis
31
is lactose a reducing or non-reducing disacchride and what is the reason
it is a reducing disaccharide because the anomeric carbon of the glucose residue is available for oxidation
32
what is the abbreviated name of lactose
Gal (β1→4) Glc
33
what does sucrose contain
glucose and fructose
34
why is sucrose a non-reducing sugar
it contains no free anomeric carbon atom; the anomeric carbons of both monosaccharide units are involved in the glycosidic bond
35
what is the abbreviated name of trehalose
Glc(α1↔1α)Glc
36
what is trehalose composed of and is it a reducing or non-reducing sugar
D-glucose | nonreducing sugar
37
what is the function of trehalose in nature
is a major constituent of the circulating fluid (hemolymph) of insects, serving as an energy-storage compound