7. Proteins
• Made up of polymers of amino acids.
• 20 primary amino acids exist.
• A polymer of 3 or more amino acids
forms a polypeptide.
8. Proteins
• Primary Structure
– Linear sequence of amino acids.
• Secondary Structure
– Form helices or sheets due to their structure.
• Tertiary Structure
– A folded protein.
• Quaternary Structure
– 2 or more polypeptide chains bonded together.
11. Enzymes
• Are proteins.
• Are considered
biological catalysts.
– Speed up a chemical
reaction without being
altered.
• Names often end in “-
ase.”
– Ex. Lipase, carbohydrase.
• Act on a substrate.
• Proteins, including
enzymes, can be
denatured.
12. Nucleic Acids
• DNA and RNA.
– (DNA - deoxyribonucleic acid,
– (RNA - ribonucleic acid).
• Is the “hereditary molecule.”
• Contains genes that code for a certain product.
• DNA is translated into RNA which is used to produce a
protein or other product.
13. Nucleic Acid Structure
• DNA nucleotides
– Building blocks of DNA.
• RNA nucleotides
– Building blocks of RNA.
19. The term carbohydrate is derived from the French term : hydrate de carbone
Compounds composed of C, H, and O
Empirical formula (CH2O)n when n = 5 then C5H10O5
Not all carbohydrates have this empirical formula: e.g. deoxysugars, amino
sugars etc
Carbohydrates are the most abundant compounds found in nature (cellulose:
100 billion tons annually).
CARBOHYDRATES
20. A - Methods of Classification:
1-One method of classification is based on whether the
carbohydrate can be broken down into smaller units.
Monosaccharides: simple sugars cannot be broken down
into smaller units by hydrolysis.
1. Disaccharides: can be broken down into two
monosaccharide units.
2. Oligosaccharides: can be broken into three to six
monosaccharide units.
3. Polysaccharides: composed of 7 or more
monosaccharide units.
21. Carbohydrates Classification
2-Another method is based on the number of carbons found in a
simple sugar.
If it has 3 carbons it is called a triose.
If it has 4 carbons it is called a tetrose.
If it has 5 carbons it is called a pentose.
If it has 6 carbons it is called a hexose.
23. Stereoconfigurations of simple sugars
-Asymmetric carbon atom: It Is the carbon atom that is
attached to 4 different groups.
- All monosaccharides have it except dihydroxyacetone.
- Different isomers are possible based on the presence of
number of asymmetric carbon atoms
24. Optical Isomerism
The presence of asymmetric
carbon atoms also confers optical
activity on the compound. When
a beam of plane-polarized light is
passed through a solution of an
optical isomer, it rotates either to
the right, dextrorotatory (+),
or to the left, levorotatory (–).
• Isomerism in Monosaccharides
25. Carbohydrate Anomers
Anomers are carbohydrates that differ by the stereo-configuration of
the carbon involved in ring formation.
The α anomer always has the OH group oriented in a downward
fashion on the anomeric carbon of a D-sugar.
β anomer always has the OH group oriented in an upward fashion on
the anomeric carbon of a D-sugar.
26. Important Carbohydrates
Monosaccharides: composed of three
to seven carbon atoms.
1- Glucose: The most abundant
hexose in our diet.
•The building block of complex
carbohydrates.
•Component of the disaccharides:
sucrose, maltose and lactose.
•Found in the polysaccharides: starch,
cellulose and glycogen.
27. Diabetes mellitus (DM)
Clinical correlate: Diabetes mellitus (DM) in which a person
has high blood glucose level.
There are three main types of diabetes mellitus.
1. Type 1 DM results from the body's failure to produce
insulin.
2. Type 2 DM results from insulin resistance, a condition in
which cells fail to use insulin.
3. Gestational diabetes
28. Glucose determination using urine dipstick
• The dipstick has the enzyme glucose oxidase on its
surface – this oxidises the glucose into hydrogen
peroxide and gluconic acid.
• The hydrogen peroxide will oxidise an indicator
chemical on the dipstick, which changes color.
• The exact color change is related to the
concentration of glucose in the urine sample.
• The color can be compared with a color chart to
give a reading for the glucose concentration.
29. • Fasting and postprandial or random blood sugar
• Glycated hemoglobin: It is formed in a non-
enzymatic pathway by hemoglobin's exposure to
plasma glucose.
• In diabetes mellitus, higher amounts of glycated
hemoglobin, indicating poorer control of blood
glucose levels.
Blood Glucose determination
30. Galactose
• Galactose is the C-4 epimer of glucose.
• Found in the disaccharide, lactose.
C
C
C
C
CHO
OH
H
OH
HO
H
H
HO
H
CH2OH
H,OH
O
H
H
OH
CH2OH
H
OH
HO
H
Clinical correlate: Galactose is a component of the antigens
present on blood cells that determine blood type within
the ABO blood group system. In O and A antigens, there are
two monomers of galactose on the antigens, whereas in the B
antigens there are three monomers of glucose.
31. Fructose
Fructose is a keto sugar.
Fructose is sweetest of the
carbohydrates (Fructose is
regarded as being 1.73 times as
sweet as sucrose).
Fructose is the energy source for
sperm motility
32. 1-Amino sugars: They are formed by replacing the hydroxyl
group (at C2 usually) of monosaccharides by amino group.
Important derivatives of monosaccharides
33. -Are formed by removal of an oxygen atom usually
from 2 nd carbon atom
-one quite ubiquitous deoxy sugar is 2’-deoxy ribose
which is the sugar found in DNA
2-Deoxy sugars
34. Sugar acids are formed by the oxidation of
aldehyde C1 (Aldonic acid) or terminal hydroxyl
group at C6 of aldose sugar (uronic acid)
-or both (saccharic) to form carboxylic group.
-L-ascorbic acid(vitamin C) is a sugar acid.
Note: Glucuronic acid is involved in detoxification
of bilirubin and other foreign compounds.
3-Sugar acids
35. Are formed by the reduction of the carbonyl group
(aldehyde or ketone ) of monosaccharide
4-Sugar alcohols
36. - Hydroxyl groups of sugars can be esterified to form Acetates,
phosphates, benzoates etc.
-Sugars are phosphorylated at terminal C1 hydroxyl group or at
other places .
At terminal hydroxyl: Glucose-6-P or ribose-5-P.
At C1 hydroxyl group: Glucose-1-P .
At both places: Fructose 2,6 bisphosphate
- Metabolism of sugars inside the cells starts with phosphorylation.
-Sugar phosphates are also components of nucleosides and
nucleotides.
5-Sugar Esters
37. They are formed by the reaction of the hydroxyl group of
anomeric carbon with the hydroxyl group of any other
molecule with the elimination of water.
A glycosidic bond is formed.
6-Glycosides
38. 1. Osazone formation
2. Reduction
3. Oxidation
4. Action of alkali
5. Action of acid
6. Glycoside formation
7. Ester formation
Reactions of monosaccharides
39. -Used for the identification of sugars
-Consists of reacting the monosaccharide with phenyl hydrazine
-A crystalline compound with a sharp melting point and a
characteristic shape is obtained
D-fructose and D-mannose give the same needle shaped osazone
crsytals as D-glucose
-Seldom used these days for identification
-HPLC or mass spectrometry is used now a days for the
identification of sugars
Formation of osazones
41. Aldoses may be oxidized to 3 types of acids
1. Aldonic acids: aldehyde group is converted to a
carboxyl group e.g. Glucose --- Gluconic acid
2. Uronic acids: aldehyde is left intact and primary
alcohol at the other end is oxidized to COOH e.g.
Glucose --- Glucuronic acid
3) Saccharic acids: (glycaric acids) – oxidation at both
ends of monosaccharide) e.g. Glucose ---- Gluco
saccharic acid
Oxidation reactions
42. -Either done catalytically (hydrogen and a catalyst) or
enzymatically
-The resultant product is a polyol or sugar alcohol
-Glucose forms sorbitol (glucitol)
-Mannose forms mannitol
-Fructose forms a mixture of mannitol and sorbitol
-Glyceraldehyde forms glycerol
Reduction
43. -Monosaccharides are normally stable to dilute acids, but are
dehydrated by strong acids
-D-ribose when heated with concentrated HCl yields furfural
-D-glucose under the same conditions yields 5-hydroxymethyl furfural
- Forms the basis of Molisch test, Seliwanoff test and Bial’s Test
Action of strong acids on monosaccharides
44. -In mild alkaline conditions Enediols are formed
- Enediols are highly reactive sugars and are powerful reducing agents.
-This allows the interconversion of D-mannose, D-fructose and D-glucose
- Strong alkalis cause Decomposition of sugars.
Action of Alkalies on sugars
45. Important Carbohydrates
Disaccharides*
composed of 2 monosaccharide units.
1. Maltose - malt sugar.
• Used in cereals, candies and the brewing of
beverages.
• Composed of two D-glucose sugars joined by an α-
1,4 linkage.
O OHH
H
HH
H
O
H
OHOH H H
OH OH
OH
OH
CH2OH CH2OH
H
46. Important Carbohydrates
Disaccharides*
composed of 2 monosaccharide units.
2. Lactose - milk sugar.
• Found in milk and milk products.
• Composed of one galactose and one glucose unit
joined by a β-1,4 linkage.
OH
H
H
OH H
OH
OH
CH2OH
H
O
CH2OH
OH
HOH
H
H
OH
H
O
47. Important Carbohydrates
Disaccharides*
composed of 2 monosaccharide units.
3. Sucrose - table sugar.
• Product of sugar cane and sugar beets.
• Composed of one glucose and one fructose unit.
• Linkage is at both anomeric carbons.
O O
OH
H
OH
H
H
O
H
H
H
OH H
HOH
CH2OHOH
CH2OH
CH2OH
48. Important Carbohydrates
Polysaccharides*
composed of many (more than 10) monosaccharide units.
• 1- Cellulose:
• Major structural material of plant cells.
• Consists of many glucose units joined by β-1,4
linkages.
49. Important Carbohydrates
Polysaccharides*
composed of many (more than 10) monosaccharide units.
2. Starch:
• Storage form of glucose found in rice wheat, potatoes, grains
and cereals.
• Consists of many glucose units joined by α-1,4 linkages.
• Maltose is the disaccharide starting material.
50. Important Carbohydrates
Polysaccharides*
composed of many (more than 10) monosaccharide units.
3. Glycogen:
• Animal starch. Storage form of glucose found in the liver and
muscle of animals.
• Contains many highly branched glucose units.
• Joined by α-1,4 linkages and branched by α-1,6 linkages.
51. Important Carbohydrates
Polysaccharides*
composed of many (more than 10) monosaccharide units.
4. Dextrin:
• Mixture of branched and un-branched soluble
polysaccharides produced by partial hydrolysis of
starch by acids or amylases.
52. Reducing sugars
• Any sugar that contains either:
1- A free aldehyde group.
2- An α-hydroxy ketone group.
3- A hemiacetal linkage
• The presence of any of these groups allows the
carbohydrate to undergo easy oxidation.
• If the sugar gets oxidized it causes reduction.
• Thus the name “reducing sugar”.
54. Molisch Test1Exp.
• It is the general test for all carbohydrates.
• Monosaccharides give a rapid positive test.
Disaccharides and polysaccharides react
slower.
55. Molisch Test1Exp.
• The Molisch reagent dehydrates
pentoses to form furfural.
• dehydrates hexoses to form 5-
hydroxymethyl furfural.
• The furfurals further react with -
naphthol present in the test
reagent to produce a purple
product.
56. Molisch Test1Exp.
Method:
• 1ml test solution + 2 drops of α-naphthol
• mix well
• add conc. H2SO4 down the side of the tube to form the
ring at the interface of the two layers.
- ve + ve
57. Fehling's Test2Exp.
• This test is used to differentiate between reducing
and non reducing sugars.
• A reducing sugar reacts with Fehling's reagent in
alkaline medium to form an orange to red
precipitate.
• Fehling's reagent is commonly used for reducing
sugars but is known to be not specific for aldehydes.
• Positive result is detected by reduction of the deep
blue solution of cupric (II) to a red precipitate of
insoluble cuprous oxide (Cu2O).
58. Fehling's Test2Exp.
• Positive result is detected by reduction of the
deep blue solution of cupric (II) to a red
precipitate of insoluble cuprous oxide (Cu2O).
59. Fehling's Test2Exp.
• The sucrose does not react with Fehling's reagent. Sucrose is a
disaccharide of glucose and fructose. Most disaccharides are
reducing sugars (e.g. lactose and maltose)
• Sucrose is non-reducing sugar because the anomeric carbon of
glucose is involved in the glucose- fructose bond and hence is
not free to form the aldehyde in solution.
60. Fehling's Test2Exp.
• Fehling's Reagent: 2solutions are required:
*Fehling's “A"
uses 7 g CuSO4.5H2O dissolved in distilled water
containing 2 drops of dilute sulfuric acid.
*Fehling's "B"
uses 35g of potassium tartrate and 12g of NaOH in 100
ml of distilled water. .
62. Exp. 3 Benedict's Test
• This test is used also to differentiate between
reducing and non reducing sugars.
• It works on the same principle but Benedict is more
stable than Fehling's reagent.
• Benedict's reagent contains blue copper(II) sulfate
(CuSO4) · 5H2O which is reduced to red copper(I)
oxide by aldehydes, thus oxidizing the aldehydes to
carboxylic acids.
• The copper oxide is insoluble in water and so
precipitates. The colour of the final solution ranges
from green to brick red depending on how many of
the copper (II) ions are present.
64. Exp. 4 Barfoid Test
• It is a test used to differentiate between monosaccharides
and disaccharides. This reaction will detect reducing
monosaccharides in the presence of disaccharides. This
reagent uses copper ions to detect reducing sugars in an
acidic solution. Barfoed's reagent is copper acetate in
dilute acetic acid (pH 4.6)
• Reducing monosaccharides are oxidized by the copper
ions in a weak acidic medium to form a carboxylic acid
and a reddish ppt of Cu2O (cuprous oxide).
• Reducing disaccharides (lactose but not sucrose) undergo
the same reaction but at slower rate.
65. Exp. 4 Barfoid Test
Method:
• 1 ml of the solution to be tested + 2 ml of freshly
prepared Barfoed's reagent.
• Place test tubes into a boiling water bath and heat for
2 minutes.
• Remove the tubes from the bath and allow to cool.
• Formation of a green, red, or yellow precipitate is a
positive test for reducing monosaccharides.
• Do not heat the tubes longer than 3 minutes, as a
positive test can be obtained with disaccharides if
they are heated long enough.
66. Exp. 5 Seliwanoff Test
• The test reagent dehydrates
ketohexoses to form 5-
hydroxymethylfurfural.
• 5-hydroxymethylfurfural
further reacts with resorcinol
present in the test reagent to
produce a red product within
two minutes.
• Aldohexoses react to form the
same product, but do so more
slowly.
67. Exp. 5 Seliwanoff Test
Method:
• 1/2 ml of a sample + 2ml of Seliwanoff's reagent (a solution of
resorcinol and HCl) is added.
• The solution is then heated in a boiling water bath for two minutes.
• A positive test is indicated by the formation of a red product.
• In case of sucrose, avoid over-boiling because sucrose may be
hydrolyzed to its component (glucose and fructose) and gives false
positive result.
+ ve- ve
68. Exp. 6 Hydrolysis Test
• Sucrose is the only non-reducing sugar so it
does not reduce the alkaline Cu solutions
(Fehling and Benedict). Sucrose must first be
hydrolyzed to its component and then test for.
69. Exp. 6 Hydrolysis Test
Method:
• 6 ml of 1% sucrose in a test tube + 2 drops of
concentrated hydrochloric acid (HCl).
• Heat the tube in a boiling water bath for 15
minutes.
• Then test for Fehling, Benedict and all the
previous tests.
70. Exp. 7 Iodine Test
(Test for Polysaccharides)
1- Starch:
• 1/2 mL of the fresh starch solution + 1 drop of
the iodine solution.
• A dark blue color indicates a positive test for
starch.
• If the yellow color of the iodine reagent simply
becomes diluted, no starch is present.
• Record the observation as positive (blue) or
negative (yellow).
71. Exp. 7 Iodine Test
(Test for Polysaccharides)
2- Dextrin:
• 1/2 mL of the fresh dextrin solution + 1 drop
of the iodine solution.
• A violet color indicates a positive test for
dextrin.
• If the yellow color of the iodine reagent simply
becomes diluted, no dextrin is present.
• Record the observation as positive (violet) or
negative (yellow).
72. Exp. 8 The preparation of osazone
• Phenyl hydrazine reacts with normal carbonyls
to produce phenyl hydrazones.
RCR
O
NHNH2
H+
RCR
N
N
H
73. The preparation of osazone8Exp.
• 1- Sugars undergo a variation of this reaction in
which 3 molecules of phenylhydrazine react with the
sugar to produce a 1,2-diphenylhydrazone.
• These 1,2-diphenylhydrazones are known as
osazones.
C
OH
C
C
C
C
CH2OH
OHH
HO H
OHH
OHH
glucose
NHNH2
CNNH
C
C
C
CH2OH
H
HO H
OHH
OHH
CNNH
3
osazone
74. The preparation of osazone8Exp.
• Because both carbons 1 and 2 are involved in
the reaction C-2 epimers produce the same
osazone.
C
OH
C
C
C
C
CH2OH
OHH
HO H
OHHO
OHH
glucose
NHNH2
CNNH
C
C
C
CH2OH
H
HO H
OHHO
OHH
CNNH
3
osazone
C
OH
C
C
C
C
CH2OH
HHO
H
OH
OHH
HO
H
NHNH2
3
mannose
75. The preparation of osazone8Exp.
• Ketoses with configurations identical to aldoses
below C-2 give the same osazones e.g. glucose
and fructose.
• Explain glucose and fructose form the same
osazone?
C
OH
C
C
C
C
CH2OH
OHH
HO H
OHH
OHH
glucose
NHNH2
CNNH
C
C
C
CH2OH
H
HO H
OHH
OHH
CNNH
3
osazone
CH2OH
C
C
C
C
CH2OH
O
H
OHH
OHH
HO
NHNH2
3
fructose
76. The preparation of osazone8Exp.
Characteristics of osazones:
• Have a characteristic shape.
• Have characteristic melting points.
• Specific time and whether the osazone is
formed from hot solutions or only on cooling.
79. The preparation of osazone8Exp.
Method:
• 1/2 g of phenyl hydrazine +
1 spoon sodium acetate +
2ml of glucose solution
• BWB (45 min) until yellow
crystals appear
• cold and examine a sample of
crystals under microscope.
• Compare the crystal shapes with
the supplied photographs.
