Week-1 Midterms Biolec
Week-1 Midterms Biolec
Week-1 Midterms Biolec
-The most abundant are Disaccharides, • The solubility to ordinary solvents is inversely
consisting of two monosaccharide units. proportional to the complexity of their structure.
Typical in sucrose (sugar cane), which ( the lesser its complexity the more soluble it is)
consists of the six-carbon sugar D-glucose • Both mono and disaccharides are sweet, while
D-fructose. starches and cellulose are tasteless
-All common monosaccharides and Reducing and Nonreducing Sugars
Disaccharides have names ending with
the suffix "ose" • Reducing Sugars: Glucose, Maltose, Fructose,
Lactose and Galactose
TYPICAL DISACCHARIDE
SUCROSE= glucose + fructose
• The presence of a double band and a negative 4. Pentoses
charge in the enol anion makes glucose an active
• Are monosaccharides containing 5 carbon
reducing substance.
atoms.
• Sucrose is the most common nonreducing
• They are not found in nature as such they occur
sugar.
in the form of complex carbohydrates like
• Non reducing sugar do not contain active ketone pentosans, gums, xylans, and arabans which only
or aldehyde group. yield pentoses
Examples of Monosaccharides • Like hexoses they possess strong reducing
property, forming characteristic osazone crystals
1. Glucose/ Dextrose/ Grape sugar
with phenyldrazine and are optically active
• It is widely distributed in nature
• Pentoses are not however fermented by Baker's
• Together with fructose, it is found in fruit juices yeast
• It appears as white or yellowish white crystalline • On prolonged heating with mineral acids,
solid that is soluble in water pentoses yield furfural. This can be distilled off
and when brought in contact with aniline acetate
• It is one of the sweetest sugars, excelled only by paper, produces characteristic red color
fructose and sucrose
5. Desoxy sugars
• Commercially it is produced by the hydrolysis of
starch and appears as colorless or faintly yellow • are true carbohydrates but the hydrogen and
syrupy liquid oxygen in their molecules are not in such
proportion as that found in a molecule of water.
• It is readily absorbed through the digestive tract This is due to the substitution of one of the
and it is the only sugar present in the blood hydroxyl groups with hydrogen, so they contain
• In conditions where carbohydrate metabolism is one oxygen less than the sugars from which they
disturbed, as in DM (Diabetes mellitus), the are derived
amount in the blood is increased and glucose 6. Monosaccharide Esters
finds its way into the urine
• Monosaccharides form esters with phosphoric
2. Fructose/ Levulose/ Fruit sugar acid which appears to be a prerequisite to many
• It is found along with glucose in many fruits and physiological reactions
vegetables • The hydroxyl groups are esterified with
• It is commercially prepared by the hydrolysis of phosphates in the presence of appropriate
inulin enzyme
• Because of the presence of the aldehyde group, • Example: (1) Starch and glycogen which yield
it reduces alkaline metallic solutions and forms glucose (2) Inulin which yields only fructose
osazone crystals
❖ Starch
❖ Lactose/ Milk sugar
• Is found abundantly in the plant kingdom
• It is found in large amount in milk particularly in fruits, cereals, seeds, bulbs and
tubers
• In excessive secretion of the mammary gland as
in lactating women, it may appear in the urine • Occurs in the form of granules
• It may also be eliminated through the urine, in • Starch granules are made up of amylose (98%)
normal individuals after ingesting large amounts which is linear in structure, and amylopectin which
of milk or lactose, and in nursing infants suffering consists of highly branched chains
from digestive disturbances
• Raw starch is insoluble on cold water
• Like maltose it reduces alkaline metallic
• Prolonged heating or grinding causes the
solutions and forms characteristic osazone
disintegration of the granules liberating the
crystals due to the presence of the aldehyde
amylose which is slightly soluble in water
group
• This is responsible for the deep blue color
• Lactose is not acted upon by yeast but is
produced with iodine due to the formation of
fermented by Escherichia coli
starch iodine; amylopectin produces purple color
• Sour milk is formed after the conversion of
• The hydrolysis of starch either by action of
lactose into lactic acid by microorganisms like
amylolytic enzyme or acid gives rise to split
Lactobacillus acidophilus and Lactobacillus
fragments of gradually diminishing molecular size
vulgaris
and complexity with simultaneous production of
• It is not very soluble in water and is not as sweet maltose
as other sugars
• In the presence of the enzyme maltase, maltose • They are amorphous, white powder, soluble in
is converted into glucose. ordinary solvents but insoluble in alcohol and
ether
• In acid, the final product is glucose
• They are dextrorotatory and non — fermentable
• The enzymes amylases catalyzing the
by yeast
hydrolysis of starch have been divided into 2
classes: • Dextrins upon hydrolysis by amylase yield
maltose, by acids, they give glucose
α— amylases like those of the pancreatic and
salivary, split a — 1,4 — glucosidic bonds (except • They are precipitated from their clear, colorless
for those of maltose) in random fashion solution by alcohol, forming a sticky, gummy
β— amylase, such as barley and malt, attack mass which are used d mucilage
polysaccharide chains effecting successive
• They are widely used in infant feeding
removal of disaccharides
• Many of breakfast foods and malt preparations
❖ Inulin
for beverages also contain dextrin
• It is found in the bulb of onions and garlic
❖ Cellulose
• It is a white, odorless, tasteless powder, easily
• Purest source is cotton
soluble in hot water but slightly soluble in cold
water and insoluble in 60% alcohol • It forms the supporting tissues of plants
• It does not give blue color with iodine solution • It is practically insoluble, being dissolved only in
certain special reagents like Schweitzer's
• Optically active
ammoniacal cupric hydroxide and zinc chloride in
• Thru the hydrolyzing action of either acid or the HCI solution
enzyme inulase, insulin yields only fructose
• It does not give a blue color with iodine
❖ Glycogen/ Animal Starch
• It is not hydrolyzed by dilute acids
• Found mostly in the liver as storage material
• With strong nitric acid and concentrated sulfuric
• Found in the muscles as a source of energy acid, it forms nitrocellulose
• It has been found to occur also in yeast, algae • When heated for some time with concentrated
and fungi acids, it liberates a disaccharide which is
subsequently split into 2 molecules of D —
• It differs from starch in being soluble in cold glucose
water, forming an opalescent solution, from which
it can be precipitated by ethyl alcohol and in • Cellulose plays an important role in human
giving with iodine a red instead of a blue color physiology by furnishing bulk (roughage) which
stimulates peristalsis
• Like starch, glycogen upon the hydrolysis by
amylase yields maltose; with acid, the end • Under suitable conditions, cellulose is oxidized
product is glucose by nitric oxide, giving rise to substances which are
soluble in the slightly alkaline body fluids
• β - amylase hydrolyzes glycogen incompletely
into maltose and limit dextrin ❖ Hemicellulose
• Analysis of tissues for glycogen depends upon • Group of carbohydrates which differ from
solution in hot alkali, precipitation with alcohol, cellulose in that they are hydrolyzed upon boiling
acid hydrolysis of the precipitate and quantitative with mineral acids
determination of glucose
• Unlike other polysaccharides, they are not
❖Dextrins readily digested by amylase
• These are intermediary products of starch • The products of its hydrolysis are pentoses and
hydrolysis hexoses
• Pentosans is a class of hemicellulose liberates Glycolysis- conversion of
pentose on hydrolysis. They are widely distributed pyruvate/lactate + ATP from glucose
in the plant kingdom. Example: Gum Arabic Glycogenolysis- (glycogen + lysis)
breakdown of stored glycogen to
• Hexosans is represented by the galactans,
glucose
which are widely distributed in plants. Upon
Glycogenesis- (glycogen + genesis)
hydrolysis, they give galactose. Example: Agar
conversion/formation of excess
Agar
glucose into glycogen stored in liver
• Hexo— pentosans this group is represented by and/ skeletal muscles.
pectins which are colloidal carbohydrates. They Lipogenesis- (lipid + genesis)
are responsible for the jellying properties of fruits. conversion of carbohydrate to fatty
On hydrolysis, pectin yield arabinose, galactose, acids (small units of lipids)
acetic acid, methyl alcohol, and galacturonic acid Gluconeogenesis- conversion of non-
carbohydrate substances such as
❖Dextrans amino acids, fatty acids, glycerol into
glucose.
• Polysaccharides produced by certain
microorganisms when grown on sugar media A. Adsorption
• Made up of units of D — glucose molecules • After thorough digestion, carbohydrates are
having glycosidic linkages reduced into simple monosaccharides
• Dextrans , synthesized by Leuconostoc • Simplified monosaccharides take places in the
dextranicium has been recommended as blood small intestine and they are carried by the portal
extenders due to their high viscosity, low osmotic circulation to the liver
pressure, low disintegration and utilization
• The different monosaccharides are absorbed at
2. Heteropolysaccharides different speed
• These are polysaccharides which on hydrolysis • Galactose and glucose are actively absorbed
yields mixtures products of monosaccharides and
derived products • Active absorption of D — glucose requires the
mediation of specific transport protein in the
• The nitrogen containing heteropolysaccharides membrane of the brush border of the intestinal
may be divided into 2 main groups mucosal cells
(1) Neutral mucopolysaccharides • Potassium and lithium ions are inhibitory to
glucose absorption
✓ Made up of N — acetyl — hexosamine and
hexose • D — fructose and D — mannose is absorbed by
facilitated transport
✓ Example: those found in bacteria and the so —
called " immunological, specific blood group • Other sugars like pentose are passively
substances absorbed by diffusion