Chapter 8: Carbohydrates

Question 1

Formula for Carbohydrates, n=?

Answer 1

(C ∙ H2O)n, where n ≥ 3.

Question 2

basic carbohydrate unit? How do they differ?

Answer 2

-monosaccharides
-differ in their number of carbon atoms and in the arrangement of the H and O atoms attached to the carbons.

Question 3

Monosaccharides can be strung together in almost limitless ways to form?

Answer 3

Polysaccharides.

Question 4

Monosaccharides are classified according to?

Answer 4

the chemical nature of their carbonyl group and the number of their C atoms.

Question 5

What are the 2 carbonyl groups and their sugars

Answer 5

Aldehyde, aldose
Ketone,ketose

Question 6

The smallest monosaccharides, those with three carbon atoms, are? Those with four, five, six, seven, etc. C atoms are?

Answer 6

-trioses.
- tetroses, pentoses, hexoses, heptoses, etc.

Question 7

How to determine possible stereoisomers?

Answer 7

All but two of its six C atoms, C1 and C6, are chiral centers, so D-glucose is one of 2 4= 16 possible stereoisomers.

Question 8

How to differentiate between D and L sugars/determine stereochemistry?

Answer 8

If OH on the bottom chiral centre points to the right it is a D-
If OH on the bottom chiral centre points to the left it is a L-
has to be farthest from carbonyl group

Question 9

D- and L- sugars are what kind of isomer

Answer 9

enantiomers, L sugars are the mirror images of their D counterparts.

Question 10

why is the the D prefix is often omitted?

Answer 10

Because L sugars are biologically much less abundant than D sugars,

Question 11

what are epimers

Answer 11

Sugars that differ only by the configuration around one C atom

Question 12

difference between aldehyde and ketone

Answer 12

difference is the presence of a hydrogen atom attached to the C-O double bond in the aldehyde. Ketones don’t have that hydrogen

Question 13

alcohols react with the carbonyl groups of aldehydes and ketones to form?

Answer 13

hemiacetals and hemiketals,

Question 14

The hydroxyl and either the aldehyde or the ketone functions of monosaccharides can likewise react intramolecularly to form

Answer 14

cyclic hemiacetals and hemiketals

Question 15

chiral center in a carb?

Answer 15

carbons that have both hydrogen and hydroxyl

Question 16

what are anomers. what are the two types?

Answer 16

when the hydroxyl attacks the carbonylit can do so from either side, thus generating two different stereoisomers

It can either attack from this side, pushing the new hydroxyl down, resulting in the alpha anomer, or
it can attack from this side pushing the new hydroxyl up, resulting in the beta anomer,

Question 17

If a cyclic monosaccharide has a six-membered ring we will call it a ?

Answer 17

pyranose

Question 18

Sometimes the hydroxyl on carbon four can do the attacking, resulting in a five-membered ring which we will call a?

Answer 18

furanose

Question 19

Haworth projections are used to draw?

Answer 19

cyclic monosaccharides

Question 20

a way in which cyclic sugars can convert from one anomer to another?

Answer 20

This alpha glucose might go back to the linear form and then cyclize again to form the beta anomer.

Question 21

why is glucose the most abundant monosaccharide in nature.

Answer 21

Only β -D-glucose can simultaneously have all five of its non-H substituents in equatorial positions.

Question 22

which anomer is preferred for glucose? !

Answer 22

In fact, for glucose, the beta anomer is preferred because the hydroxyl on the anomeric carbon will be in the equatorial position versus axial in the alpha anomer.

Question 23

Oxidation of an aldose converts its aldehyde group to a carboxylic acid group, called an? end in?

Answer 23

aldonic acid
-onic acid

Question 24

Oxidation of the primary alcohol group of aldoses yields? end in?

Answer 24

uronic acids
-uronic acid
changes most bottom Carbon

Question 25

Aldoses and ketoses can be reduced under mild conditions—for example, by treatment with NaBH4 —to yield polyhydroxy alcohols known as? end in?

Answer 25

alditols,
-itol

Question 26

Monosaccharide units in which an OH group is replaced by H are known as ?

Answer 26

deoxy sugars.

Question 27

In ____ one or more OH groups have been replaced by an amino group, which is often acetylated.

Answer 27

amino sugar

Question 28

The bond connecting the anomeric carbon to the alcohol oxygen is

Answer 28

a glycosidic bond

Question 29

Saccharides bearing anomeric carbons that have not formed glycosides are termed ?

Answer 29

reducing sugars

Question 30

The identification of a sugar as nonreducing is evidence that?

Answer 30

it is a glycoside.

Question 31

what are polysaccharides?

Answer 31

Polysaccharides, which are also known as glycans, consist of monosaccharides linked together by glycosidic bonds.

Question 32

Polysaccharides are classified as either ?

Answer 32

homopolysaccharides or heteropolysaccharides if they consist of one type or more than one type of monosaccharide.

Question 33

most well known disaccharides? how many sugars? which is more abundant

Answer 33

lactose and sucrose, 2 each, sucrose

Question 34

is glucose a reducing sugar ?

Answer 34

Ye

Question 35

what is sucrose

Answer 35

the major form in which carbohydrates are transported in plants. Sucrose is familiar to us as common table sugar.

Question 36

Cellulose,

Answer 36

the primary structural component of plant cell walls (Fig. 8-8), accounts for over half of the carbon in the biosphere:

Question 37

Chitin

Answer 37

is the principal structural component of the exoskeletons of invertebrates such as crustaceans, insects, and spiders and is also present in the cell walls of most fungi and many algae. It is therefore the second most abundant biomolecule, after cellulose. Chitin is a homopolymer of β (1→4)-linked N-acetyl-Dglucosamine residues:

Question 38

Cellulose and Chitin Are what kind of Polysaccharides

Answer 38

Structural

Question 39

Starch and Glycogen Are what kind of Polysaccharides

Answer 39

Storage

Question 39

Starch and Glycogen Are what kind of Polysaccharides

Answer 39

Storage

Question 40

Glycogen,

Answer 40

the storage polysaccharide of animals, is present in all cells but is most prevalent in skeletal muscle and in liver, where it occurs as cytoplasmic granules