Monosaccharides

Monosaccharides (from Greek monos: single, sacchar: sugar),

also called simple sugars, are the simplest forms of sugar and
the most basic units (monomers) from which
all carbohydrates are built.[1][2]
They are usually colorless, water-soluble,
and crystalline solids. Contrary to their name (sugars), only
some monosaccharides have a sweet taste. Most
monosaccharides have the formula CnH2nOn (though not all
molecules with this formula are monosaccharides).
Examples of monosaccharides
include glucose (dextrose), fructose (levulose), and galactose.
Monosaccharides are the building blocks
of disaccharides (such as sucrose and lactose)
and polysaccharides (such as cellulose and starch). The table
sugar used in everyday vernacular is itself a disaccharide
sucrose comprising one molecule of each of the two
monosaccharides D-glucose and D-fructose.[2]
Each carbon atom that supports a hydroxyl group is chiral,
except those at the end of the chain. This gives rise to a
number of isomeric forms, all with the same chemical
formula. For instance, galactose and glucose are
both aldohexoses, but have different physical structures and
chemical properties.
The monosaccharide glucose plays a pivotal role
in metabolism, where the chemical energy is extracted
through glycolysis and the citric acid cycle to provide energy
to living organisms.
Structure of Monosaccharides
All the monosaccharides have the formula as (CH2O) n. Here,
the two hydrogen atoms and one oxygen atom associate
itself to the central carbon molecule. A hydroxyl group is
formed when oxygen will bond with hydrogen. Several carbon
molecules bond together because 4 bonds can form on
carbon.
One of the carbon will form a double bond with oxygen in the
chain, which is termed as a carbonyl group. Depending upon
its position, if it is formed at the end of the chain, then, the
monosaccharides are said to belong to the aldose family and
if it formed in the middle of the chain, then it belongs to the
ketose family

A large number of biologically important modified

monosaccharides exist:
 Amino sugars such as:
o galactosamine

o glucosamine

o sialic acid

o N-acetylglucosamine

 Sulfosugars such as:

o sulfoquinovose
 Others such as:
o ascorbic acid

o mannitol

o glucuronic acid
  Glucose

Preparation of Glucose
1. From sucrose (cane sugar): We get glucose and fructose in
exactly equal amounts if sucrose is boiled with dilute HCl and
H2SO4 in an alcoholic solution.
C12H22O11(Sucrose)+ H2O → C6H12O6 (Glucose)+
C6H12O6 (Fructose)
2. From Starch: When hydrolysis of starch is carried out in
boiled and diluted H2SO4 at 393 K under pressure, we get
glucose.
(C6H10O5)n (Starch or cellulose) + nH2O + H+ →
nC6H12O6 (Glucose)
.
Glucose molecules can be broken down by glycolysis in the
process of cellular respiration. Glucose can be connected in
long strings of monosaccharides to form polysaccharides. In
plants, this thing is produced as cellulose. In plants, each cell
is surrounded by cellulose that helps plants stand tall and
turgid.
Glucose is by far the most common carbohydrate and
classified as a monosaccharide, an aldose, a hexose, and is a
reducing sugar. It is also known as dextrose, because it is
dextrorotatory (meaning that as an optical isomer is rotates
plane polarized light to the right and also an origin for the D
designation. Glucose is also called blood sugar as it circulates
in the blood at a concentration of 65-110 mg/dL of blood.
Glucose is initially synthesized by chlorophyll in plants using
carbon dioxide from the air and sunlight as an energy source.
Glucose is further converted to starch for storage.

Up until now we have been presenting the structure of

glucose as a chain. In reality, an aqueous sugar solution
contains only 0.02% of the glucose in the chain form, the
majority of the structure is in the cyclic chair form. Since
carbohydrates contain both alcohol and aldehyde or
ketone functional groups, the straight-chain form is easily
converted into the chair form - hemiacetal ring structure.
Due to the tetrahedral geometry of carbons that ultimately
make a 6 membered stable ring , the -OH on carbon #5 is
converted into the ether linkage to close the ring with carbon
#1. This makes a 6 member ring - five carbons and one
oxygen.

 Fructose
Fructose belongs to the ketose group. Differently shaped
monosaccharides break down the specific enzyme. If
fructose, combines with other monosaccharides then they
form oligosaccharides. Sucrose has a fructose molecule
joined with a glucose molecule with the help of a glycosidic
bond.

 Fructose is a type of sugar known as a monosaccharide.

 Like other sugars, fructose provides four calories per
gram.
 Fructose is also known as “fruit sugar” because it
primarily occurs naturally in many fruits. It also occurs
 naturally in other plant foods such as honey, sugar beets,
sugar cane and vegetables.
 Fructose is the sweetest naturally occurring
carbohydrate and is 1.2–1.8 times sweeter than sucrose
(table sugar).
 Fructose metabolism does not require insulin and has a
low impact on blood glucose levels.

There are many different types of sugars, some of which are

more common than others. Fructose is a type of sugar known
as a monosaccharide, or a “single” sugar, like glucose.
Monosaccharides can bond together to form disaccharides,
the most common of which is sucrose, or “table sugar.”
Sucrose is 50% fructose and 50% glucose. Fructose and
glucose have the same chemical formula (C6H12O6) but have
different molecular structures, which makes fructose 1.2–1.8
times sweeter than sucrose. In fact, fructose is the sweetest
naturally occurring carbohydrate. In nature, fructose is most
often found as part of sucrose. Fructose is also found in
plants as a monosaccharide, but never without the presence
of other sugars.

Where does fructose come from?

Sometimes called “fruit sugar,” fructose is a naturally

occurring sugar found primarily in fruits (such as apples,
dates, figs, pears and prunes), but also in vegetables (such as
artichokes, asparagus, mushrooms, onions and red peppers),
honey, sugar beets and sugar cane. Pure fructose is produced
commercially from corn or sucrose into a crystalline form for
use as an ingredient in packaged foods and beverages.
Although fructose is in high fructose corn syrup (a 55:45
mixture of the monosaccharides fructose and glucose),
crystalline fructose should not be confused with high fructose
corn syrup.

 Galactose
Galactose is produced by mammals in the form of milk.
Lactose holds a lot of energy in its bonds and for breaking
down the bonds apart, specific enzymes are developed by off
springs of mammals.
Galactose is a monosaccharide and has the same chemical
formula as glucose, i.e., C6H12O6. It is similar to glucose in its
structure, differing only in the position of one hydroxyl group.
This difference, however, gives galactose different chemical
and biochemical properties to glucose.
The major dietary source of galactose is lactose,
a disaccharide formed from one molecule of glucose plus
one of galactose

 Mannose
As a natural sugar, mannose is a type of hexose that is
abundant in many different types of fruits. Since
mannose is rarely used for glycolysis in mammals,
studies on the role of mannose have not attracted much
attention. Glycosylation of specific proteins was thought
to be the major function of mannose. Surprisingly,
during the past few years, mannose was found to be
 effective in promoting immune tolerance and
suppressing inflammatory diseases related to
autoimmunity and allergy. Moreover importantly,
mannose was also found to be efficient in suppressing
tumors by suppressing glycolysis and enhancing
chemotherapeutic agents. In this review, we summarize
the recent studies of mannose on antitumor properties
and anti-inflammatory characteristics. We emphasize
that mannose could play a beneficial role in the
treatment of a variety of diseases, including cancers and
inflammatory diseases, and could be a novel therapeutic
strategy that deserves continued evaluation.

Oligosaccharides
Oligosaccharides represent carbohydrates that contain
between 3 and 10 single sugar residues and are not relatively
abundant in the diet when compared to other more common
carbohydrates like those in the disaccharide category.
Common oligosaccharides include raffinose, stachyose, and
verbascose. These oligosaccharides can be found in relatively
abundant levels in legumes, whole grains, some cruciferous
vegetables, and some fruits. Humans lack the ability to
properly digest these carbohydrates because we lack the
digestive enzyme ⍺-galactosidase, thus oligosaccharides are
not hydrolyzed and are instead passed undigested into the
lower gut. Here, the oligosaccharides are fermented and
metabolized by anaerobic bacteria. While this metabolic
process does not result in digestive discomfort or adverse
symptoms for all consumers, it has been associated with
undesirable results such as abdominal cramping and
excessive flatulence.
Despite the negative symptoms sometimes associated with
the consumption of oligosaccharides, there is also evidence
to suggest that they may be associated with some positive
health outcomes similar to those thought to be linked with
dietary fiber.4 Because of these potential health benefits,
oligosaccharides have become popular food additives, with
some manufactured oligosaccharides such as
fructooligosaccharide and lactulose being added to food
products that have been marketed as health foods

1. Disaccharide
 Lactose
The major dietary source of galactose is lactose,
a disaccharide formed from one molecule of glucose plus
one of galactose. Lactose is found only in milk; after weaning,
significant quantities of dietary lactose are found only in dairy
products Lactose levels are lower than expected in some
dairy products, where it has been used by the microbes
involved in processing the food.lactose in human milk is 7.2
g.Lactose, a byproduct of the dairy industry, can be
hydrolyzed to produce lactose hydrolysate syrup, which
contains lactose, galactose, and glucose. This syrup is used as
a sweetener in biscuits, confectionery, and some dairy
desserts. Thus, small amounts of lactose and galactose can
appear in nondairy foods
What is lactose intolerance?

Lactose intolerance is a condition in which you have digestive

symptoms—such as bloating, diarrhea, and gas—after you
consume foods or drinks that contain lactose. Lactose is a
sugar that is naturally found in milk and milk products, like
cheese or ice cream.

In lactose intolerance, digestive symptoms are caused

by lactose malabsorption. Lactose malabsorption is a
condition in which your small intestine cannot digest, or
break down, all the lactose you eat or drink.
Not everyone with lactose malabsorption has digestive
symptoms after they consume lactose. Only people who have
symptoms are lactose intolerant.
Most people with lactose intolerance can consume some
amount of lactose without having symptoms. Different
people can tolerate different amounts of lactose before
having symptoms.
Lactose intolerance is different from a milk allergy. A milk
allergy is an immune system disorder.

 Sucrose
There are many different types of sugars, the most common
of which is sucrose, otherwise known as table
sugar, granulated sugar or just plain “sugar.” If you use
sugar to bake or sweeten coffee or tea, sucrose
is probably the type of sugar you are using. Scientifically
speaking, sucrose is a type of carbohydrate, a disaccharide
made of equal parts of two monosaccharides: glucose and
fructose.
Where does sucrose come from?

Sucrose is a naturally occurring sugar found in various

amounts in plants like fruits, vegetables and
nuts. Sucrose is also produced commercially from sugar cane
and sugar beets. According to the U.S. Department of
Agriculture, the top producing regions for sugar beets in the
U.S. are western Minnesota, eastern North Dakota and
Idaho. U.S. sugar cane is produced in southern Florida, the
Mississippi Delta region of Louisiana and southern Texas.

 Maltose

 Maltose is a sugar made out of two glucose molecules

bound together.

 Even though maltose is less sweet than table sugar and

fructose, it has long been used in hard candy and frozen
desserts because of its unique tolerance to heat and
cold.

 Plant seeds also produce enzymes to release sugar from

starch as they sprout.

 People have long taken advantage of this natural process

for food production.
 The sugars and proteins in malt are very nourishing for
yeast, so malt has become important in brewing beer,
whisky and malt vinegar.

 Malted grains are also used in candies and desserts as

sweeteners.

2. Trisaccharide

 Raffinose

Raffinose is a trisaccharide composed

of galactose, glucose, and fructose. It can be found
in beans, cabbage, brussels
sprouts, broccoli, asparagus, other vegetables, and
whole grains. Raffinose can be hydrolyzed to D-
galactose and sucrose by the enzyme α-
galactosidase (α-GAL), an enzyme which in the
lumen of the human digestive tract is only
produced by bacteria in the large intestine. α-GAL
also hydrolyzes other α-galactosides such
as stachyose, verbascose, and galactinol, if present.
The enzyme does not cleave β-linked galactose, as
in lactose.

 Gentianose

 Molecular Formula C18H32O16

3. Tetrasaccharide
  Stachyose

Stachyose is a tetrasaccharide consisting

of sucrose having an alpha-D-galactosyl-(1->6)-alpha-
D-galactosyl moiety attached at the 6-position of
the glucose. It has a role as a plant metabolite and a
mouse metabolite. It is a raffinose family
oligosaccharide and a tetrasaccharide. It is
functionally related to a sucrose and a raffinose.
 Stachyose is a natural product found in Amaranthus
cruentus, Salacia oblonga, and other
organisms with data available.
 Molecular Formula C24H42O21

Polysaccharides
Polysaccharides or polycarbohydrates, are the most
abundant carbohydrates found in food. They are long-
chain polymeric carbohydrates composed
of monosaccharide units bound together by glycosidic
linkages. This carbohydrate can react with water (hydrolysis)
using amylase enzymes as catalyst, which produces
constituent sugars (monosaccharides, or oligosaccharides).
They range in structure from linear to highly branched.
Examples include storage polysaccharides such
as starch, glycogen and galactogen and structural
polysaccharides such as cellulose and chitin.
Amylose is a linear polymer of glucose mainly linked with
α(1→4) bonds. It can be made of several thousands of
glucose units. It is one of the two components of starch, the
other being amylopectin.
Polysaccharides are often quite heterogeneous, containing
slight modifications of the repeating unit. Depending on the
structure, these macromolecules can have distinct properties
from their monosaccharide building blocks. They may
be amorphous or even insoluble in water.[1]
When all the monosaccharides in a polysaccharide are the
same type, the polysaccharide is called
a homopolysaccharide or homoglycan, but when more than
one type of monosaccharide is present, they are
called heteropolysaccharides or heteroglycans.[2][3]

 Starch

 Pure starch is a white, tasteless and odorless

powder that is insoluble in cold water or
alcohol. It consists of two types of molecules:
the linear and helical amylose and the
branched amylopectin. Depending on the
plant, starch generally contains 20 to 25%
amylose and 75 to 80% amylopectin by
weight.[4] Glycogen, the energy reserve of
animals, is a more highly branched version of
amylopectin.
 In industry, starch is often converted into
sugars, for example by malting. These sugars
may be fermented to produce ethanol in the
manufacture of beer, whisky and biofuel. In
 addition, sugars produced from processed
starch are used in many processed foods.
 Mixing most starches in warm water produces
a paste, such as wheatpaste, which can be
used as a thickening, stiffening or gluing agent.
The principal non-food, industrial use of starch
is as an adhesive in the papermaking process.
A similar paste, § clothing starch, can be
applied to certain textile goods before ironing
to stiffen them.

 Glycogen

 Glycogen is the stored form of glucose that’s

made up of many connected glucose
molecules.
 Glucose (sugar) is your body’s main source of
energy. It comes from carbohydrates (a
macronutrient) in certain foods and fluids you
consume. When your body doesn’t
immediately need glucose from the food you
eat for energy, it stores glucose primarily in
your muscles and liver as glycogen for later
use.
 Your body creates glycogen from glucose
through a process called glycogenesis. Your
body breaks down glycogen for use through a
process called glycogenolysis. Several
different enzymes are responsible for these
two processes.
  An enzyme is a type of protein in a cell that
acts as a catalyst and allows certain bodily
processes to happen. There are thousands of
enzymes throughout your body that have
important functions

 Cellulose

Cellulose is an organic compound with the formula (C6H10O5)

n, a polysaccharide consisting of a linear chain of several
hundred to many thousands of β(1→4) linked D-
glucose units.[3][4] Cellulose is an important structural
component of the primary cell wall of green plants, many
forms of algae and the oomycetes. Some species
of bacteria secrete it to form biofilms.[5] Cellulose is the most
abundant organic polymer on Earth.[6] The cellulose content
of cotton fiber is 90%, that of wood is 40–50%, and that of
dried hemp is approximately 57%.[

 Chitin

Chitin based aerogels have been synthesized by many

researchers for various biological uses. Electron microscopic
analysis revealed that pore size of the chitin matrixes varied
with the freezing method employed before lyophilization. In
another study, same procedure was adopted and Chitin
aerogels were fabricated by extracting methanol or propanol
(solvents) with carbon dioxide under super critical conditions.
The prepared nano-porous aerogels demonstrated high
surface area and low density [13]. Aerogels of high porosity
were obtained after freeze drying the hydrogels
 Inulin

 Inulin is a type of prebiotic. It's not digested or

absorbed in the stomach. It stays in the bowel
and helps certain beneficial bacteria to grow.

Inulin is a starchy substance found in a wide

variety of fruits, vegetables, and herbs,
including wheat, onions, bananas, leeks,
artichokes, and asparagus. The inulin that is
used in supplements most commonly comes
from soaking chicory roots in hot water.


People commonly use inulin by mouth for
weight loss, constipation, and diabetes. It's also
used for high blood fats, including cholesterol
and triglycerides, and many other conditions,
but there is no good scientific evidence to
support most of these uses