Carbohydrates

Question 1

The word carbohydrate arose because molecular formulas of these compounds can be expressed as

Answer 1

hydrates of carbon

Question 2

The chemistry of carbohydrates is mainly the combined chemistry of two functional groups:

Answer 2

hydroxyl group and the carbonyl group

Question 3

Carbohydrates are-_____,______, or substances that give such compounds on hydrolysis

Answer 3

polyhydroxyaldehydes, polyhydroxyketones

Question 4

usually classified according to their structure as monosaccharides, oligosaccharides, or polysaccharides.

Answer 4

Carbohydrates

Question 5

The term saccharide comes from Latin (_____, _____) and refers to the sweet taste of some simple carbohydrates

Answer 5

saccharum, sugar

Question 6

The three classes of carbohydrates are related to each other through hydrolysis.

Answer 6

Monosaccharides, Polysaccharides, and Oligosaccharides

Question 7

(or simple sugars, as they are sometimes called) are carbohydrates that cannot be hydrolyzed to simpler compounds

Answer 7

Monosaccharides

Question 8

contain many monosaccharide units—sometimes hundreds or even thousands. Usually, but not always, the units are identical. Two of the most important ___________, starch and cellulose, contain linked units of the same monosaccharide, glucose.

Answer 8

Polysaccharides

Question 9

(from the Greek oligos, few) contain at least two and generally no more than a few linked monosaccharide units. They may be called disaccharides, trisaccharides, and so on, depending on the number of units, which may be the same or different.

Answer 9

Oligosaccharides

Question 10

Monosaccharides are classified according to the number of carbon atoms present (triose, tetrose, pentose, hexose, and so on) and according to whether the carbonyl group is present as an ________or______

Answer 10

aldehyde (aldose) or as a ketone (ketose).

Question 11

There are only two trioses in Monosaccharides

Answer 11

glyceraldehyde and dihydroxyacetone

Question 12

the simplest aldose

Answer 12

glyceraldehyde

Question 13

the simplest ketose

Answer 13

dihydroxyacetone

Question 14

used a capital D to represent the configuration of (+)-glyceraldehyde, with the hydroxyl group on the right; its enantiomer, with the hydroxyl group on the left, was designated L-(-)-glyceraldehyde. The most oxidized carbon (CHO) was placed at the top.

Answer 14

Emil Fischer

Question 15

If the stereogenic carbon farthest from the aldehyde or ketone group had the same configuration as D-glyceraldehyde (hydroxyl on the right), the compound was called a

Answer 15

D-sugar

Question 16

If the configuration at the remote carbon had the same configuration as L-glyceraldehyde (hydroxyl on the left), the compound was an

Answer 16

L-sugar

Question 17

These structures are called _____forms after the six-membered oxygen heterocycle pyran

Answer 17

pyranose

Question 18

formed by reaction of the hydroxyl group at C-5, with the carbonyl group. With some sugars, however, the hydroxyl group at C-4 reacts instead.

Answer 18

pyranoses

Question 19

type of cyclic monosaccharide is called a_____, after the parent five-membered oxygen heterocycle furan

Answer 19

furanose

Question 20

The most common oligosaccharides

Answer 20

disaccharides

Question 21

In a disaccharide, two monosaccharides are linked by a __________ between the anomeric carbon of one monosaccharide unit and a hydroxyl group on the other unit

Answer 21

glycosidic bond

Question 22

the disaccharide obtained by the partial hydrolysis of starch.

Answer 22

Maltose

Question 23

hydrolysis of maltose gives only

Answer 23

D-glucose

Question 24

the disaccharide obtained by the partial hydrolysis of cellulose.

Answer 24

Cellobiose

Question 25

Further hydrolysis of cellobiose gives only

Answer 25

D-glucose

Question 26

the major sugar in human and cow’s milk (4% to 8% _____)

Answer 26

lactose

Question 27

Hydrolysis of lactose gives equimolar amounts of

Answer 27

D-galactose and Dglucose

Question 28

- Some human infants are born with a disease called - They lack the enzyme that isomerizes galactose to glucose and therefore cannot digest milk. If milk is excluded from such infants’ diets, the disease symptoms caused by accumulation of galactose can be avoided

Answer 28

galactosemia

Question 29

The most important commercial disaccharide

Answer 29

Sucrose

Question 30

More than_______ are produced annually worldwide. Sucrose occurs in all photosynthetic plants, where it functions as an energy source.

Answer 30

130 million tons

Question 31

It is obtained commercially from sugar cane and sugar beets, in which it constitutes ___ %to ___% of the plant juices

Answer 31

14% to 20%

Question 32

very water soluble (2 grams per milliliter at room temperature) because it is polar due to the presence of eight hydroxyl groups on its surface

Answer 32

Sucrose

Question 33

Hydrolysis of sucrose gives equimolar amounts

Answer 33

D-glucose and the ketose D-fructose.

Question 34

contain many linked monosaccharides and vary in chain length and molecular weight.

Answer 34

Polysaccharides

Question 35

Most polysaccharides give a ______ on complete hydrolysis.

Answer 35

single monosaccharide

Question 36

the energy-storing carbohydrate of plants. It is a major component of cereals, potatoes, corn, and rice.

Answer 36

starch

Question 37

It is the form in which glucose is stored by plants for later use

Answer 37

starch

Question 38

Starch is made up of glucose units joined mainly by ________, although the chains may have a number of branches attached through 1,6-α-glycosidic bonds

Answer 38

1,4-α-glycosidic bonds

Question 39

Partial hydrolysis of starch gives maltose, and complete hydrolysis gives only

Answer 39

D-glucose

Question 40

Starch can be separated by various techniques into two fractions:

Answer 40

amylose and amylopectin

Question 41

which constitutes about 20% of starch, the glucose units (50 to 300) are in a continuous chain, with 1,4 linkages.

Answer 41

amylose

Question 42

highly branched. Although each molecule may contain 300 to 5000 glucose units, chains with consecutive 1,4 links average only 25 to 30 units in length. These chains are connected at branch points by 1,6 linkages.

Answer 42

Amylopectin

Question 43

the energy-storing carbohydrate of animals

Answer 43

Glycogen

Question 44

Like starch, it is made of ____and____ glucose units. Glycogen has a higher molecular weight than starch (perhaps 100,000 glucose units), and its structure is even more branched than that of amylopectin, with a branch every 8 to 12 glucose units

Answer 44

1,4- and 1,6-linked

Question 45

produced from glucose that is absorbed from the intestines into the blood; transported to the liver, muscles, and elsewhere; and then polymerized enzymatically

Answer 45

glycogen

Question 46

an unbranched polymer of glucose joined by 1,4-b-glycosidic bonds

Answer 46

Cellulose

Question 47

X-ray examination of cellulose shows that it consists of linear chains of cellobiose units in which the ring oxygens alternate in “______” and “______” positions.

Answer 47

forward and backward

Question 48

Many bacteria, however, do contain b-glucosidases and can hydrolyze cellulose. Termites, for example, have such bacteria in their intestines and thrive on wood (cellulose) as their main food. Ruminants (cud-chewing animals such as cows) can digest grasses and other forms of cellulose because they harbor the necessary microorganisms in their ______

Answer 48

rumen

Question 49

a nitrogen-containing polysaccharide that forms the shells of crustaceans and the exoskeletons of insects.

Answer 49

chitin

Question 50

which are obtained from fruits and berries, are polysaccharides used in making jellies.

Answer 50

Pectins

Question 51

has the same structure as D-galactose, except that the C-6 primary alcohol group is replaced by a carboxyl group.

Answer 51

D-Galacturonic acid

Question 52

one or more of the hydroxyl groups is replaced by a hydrogen atom.

Answer 52

Deoxy Sugars

Question 53

The most important example is 2-deoxyribose

Answer 53

the sugar component of DNA.

Question 54

one of the sugar hydroxyl groups is replaced by an amino group.

Answer 54

Amino Sugars

Question 55

one of the more abundant amino sugars.

Answer 55

D-Glucosamine

Question 56

b-D-glucosamine the monosaccharide unit of chitin, which forms the shells of lobsters, crabs, shrimp, and other shellfish.

Answer 56

N-acetyl form

Question 57

more precisely in terms of their organic structures

Answer 57

carbohydrates

Question 58

the chain numbered from the aldehyde carbon

Answer 58

aldoses

Question 59

the carbonyl group is located at C-2

Answer 59

ketoses

Question 60

The most oxidized carbon -_____ was placed at the top.

Answer 60

CHO

Question 61

"convert D-glucose to the cyclic a-pyranose form as a Haworth projection"

Answer 61

Converting a Fischer Projection to A Haworth Projection

Question 62

some "tricks" for converting a Fischer to a Haworth | For C1: the a anomer has OH →

Answer 62

down (for D-sugars)

Question 63

some "tricks" for converting a Fischer to a Haworth | For C1: the B anomer has OH →

Answer 63

up (for D-sugars)

Question 64

In Maltose, The ________of the left unit is linked to the C-4 _______of the unit at the right

Answer 64

anomeric carbon & hydroxyl group

Question 65

cellobiose differs from maltose only in having the b-configuration at ____ of the left glucose unit. Otherwise, all other structural features are identical, including a link from C-1 of the left unit to the hydroxyl group at ___ in the right unti.

Answer 65

C-1 & C-4

Question 66

Lactose, The anomeric carbon of the galactose unit has the b configuration at____and is linked to the hydroxyl group at ___ of the glucose unit.

Answer 66

C-1 & C-4

Question 67

Sucrose differs from the other disaccharides in that the anomeric carbons of both units are involved in the glycosidic bond; that is,___ of the glucose unit is linked via oxygen to ___ of the fructose unit..

Answer 67

C-1 & C-2

Question 68

Sucrose, an additional difference is that the fructose unit in the ____

Answer 68

furanose form

Question 69

Amino sugars: ______is also acetylated

Answer 69

NH2 group

Question 70

The main function of carbohydrate is a _____

Answer 70

short term energy