EXPT 6 - Carbohydrates (Monosaccharides & Disaccharides)

Question 1

Molecular formula of carbohydrates

Answer 1

Cn(H2O)n

Question 2

Give the three ways in which carbohydrates are classified

Answer 2

1. According to type of carbonyl group
2. According to the number of carbon atoms
3. According to the number of sugar units

Question 3

ketoses belongs to which group?

Answer 3

keto group

Question 4

aldoses belongs to which group?

Answer 4

aldehyde group

Question 5

notations that are used to describe the configurations of carbohydrates.

Answer 5

D and L notations

Question 6

the OH group is on the right

Answer 6

D notations

Question 7

the OH group is on the left

Answer 7

L notations

Question 8

It is the chiral carbon farthest from the aldehyde or ketone functional group.

Answer 8

penultimate (next-to-last) carbon atom

Question 9

it does not tell the nature of the carbonyl group, but tells the number of carbons.

Answer 9

triose

Question 10

the only two trioses

Answer 10

-glyceraldehyde (aldotriose)
-dihydroxyacetone (ketotriose)

Question 11

composed of one sugar units (simple sugars)

Answer 11

Monosaccharide

Question 12

composed of two monosaccharide units

Answer 12

Disaccharide

Question 13

a few, usually 2 – 10 monosaccharide units

Answer 13

Oligosaccharides

Question 14

are polymers of the simple sugars usually more than 10 monosaccharide units

Answer 14

Polysaccharides

Question 15

the three common monosaccharides

Answer 15

glucose
fructose
galactose

Question 16

the main type of sugar in the blood and is the major source of energy for the body’s cells

Answer 16

Glucose

Question 17

a fruit sugar, is the simplest ketonic sugar. It is the sweetest naturally occurring carbohydrate

Answer 17

Fructose

Question 18

is a C-4 epimer of glucose. It is known as the brain sugar. It supports the brain development of infants.

Answer 18

Galactose

Question 19

composed of two monosaccharide subunits hooked together by an acetal linkage

Answer 19

Disaccharides

Question 20

Disaccharides yield two _______________ upon hydrolysis

Answer 20

monosaccharides

Question 21

derived from two glucose

Answer 21

Maltose

Question 22

In maltose, ά-D-glucose linked to β-D-glucose by an _____________________.

Answer 22

ά (1-4) glycosidic bond

Question 23

a repeating disaccharide unit of starch and a product of hydrolysis of starch by the action of either enzymes or acids

Answer 23

maltose

Question 24

the juice from sprouted barley and other cereal grains.

Answer 24

malt

Question 25

essential ingredient of food preparations for invalids and babies

Answer 25

maltose

Question 26

derived from glucose + galactose

Answer 26

lactose

Question 27

Lactose is made up of β -D-galactose linked to β -D-glucose by ________________________.

Answer 27

β (1-4) glycosidic bond

Question 28

the principal sugar present in milk; it makes up about 5 to 8 percent of human milk and 4 to 6 percent of cow's milk

Answer 28

lactose

Question 29

derived from glucose and fructose

Answer 29

sucrose

Question 30

Sucrose is made up of β-D-fructose linked to an ά-D-glucose by a ___________________.

Answer 30

β (2-1) glycosidic bond

Question 31

a non reducing sugar that is most important sugar from the dietary standpoint, widely distributed in nature especially in cane sugar and sugar beets

Answer 31

sucrose

Question 32

Phloroglucinol-HCl test is used to specifically detect what sugars?

Answer 32

galactose and lactose

Question 33

produce needle-shaped yellow osazone crystals.

Answer 33

Glucose, fructose and mannose

Question 34

produce mushroom-shaped crystals

Answer 34

lactose

Question 35

produces star-shaped (flower-shaped) crystals.

Answer 35

maltose

Question 36

1. In Molisch Test, what is the principle behind the production of color at the junction of two liquids?

Answer 36

The color formed is due to the reaction of alpha-naphthol with furfural and/or its derivative formed by the dehydration of sugars concentrated sulfuric acid

Question 37

is like the Benedict’s test for reducing sugars only that it involves treating the sample with concentrated H2SO4 which results to acid hydrolysis of disaccharides forming monosaccharides

Answer 37

Trommer's test

Question 38

a reduction test that uses bismuth subnitrate which is reduced to black precipitate bismuth when reacted with a reducing sugar

Answer 38

Nylander's test

Question 39

qualitative test that distinguishes aldehydes from ketones on the principle that aldehydes are easily oxidized than ketones

Answer 39

Tollen's test (silver mirror test)

Question 40

Test for the presence of reducing sugars. It reacts with metal to form metal picrates.

Answer 40

Picric acid test

Question 41

a chemical compound formally called 2,4,6-trinitrophenol (TNP).

Answer 41

picric acid

Question 42

Positive results of picric acid test

Answer 42

formation of MAHOGANY RED SOLUTION

Question 43

a toxic yellow crystalline solid and one of the most acidic phenols.

Answer 43

picric acid (dry)