biochem
poorva
PHAR150GBiochemistryDayCarbohydrates.pptx
1
Objectives
Describe three classes of carbohydrates, how they are synthesized, specific examples of each (name, empirical and structural formulas) and their functions.
Describe digestion of Carbohydrates
| Disorder | Cause | Explanation |
| Lactose Intolerance | Genetic/ Environmental | Inability to digest and absorb lactose due to shortage of enzyme lactase |
Diseases discussed in this Class
Must Know
3
Carbohydrates
All carbohydrates are composed of carbon, hydrogen, and oxygen in a 1:2:1 empirical ratio.
The general empirical formula for a carbohydrate is CH2O.
Most carbohydrates end with the suffix -ose
Functions of Carbohydrates
What are the functions in a living organism?
ENERGY, STORAGE and STRUCTURE
E.g. Glucose, sucrose, starch (plant storage), glycogen (animal storage), cellulose (plant cell walls), chitin (insects)
Must Know
Classes of Carbohydrates
There are three major classes of carbohydrates:
Monosaccharides (simple sugars) These are the monomers Examples: glucose, fructose, galactose, and ribose.
Disaccharides are produced by joining two simple sugars. Examples: sucrose (table sugar), maltose, lactose
Polysaccharides (complex carbohydrates) are produced by joining many monosaccharides together forming a polymer molecule. Examples: amylose, glycogen, cellulose, and chitin
Monosaccharides
7
Monosaccharides (simple sugars)
Monosaccharides are building blocks of all CHO
Classified based on total no. of carbon atoms (3-7)
Trioses, tetroses, pentoses, hexoses and heptoses
5 carbons are called pentoses ex. Ribose
6 carbons are called hexoses ex. Glucose
They may exist in a linear molecule or in ring forms.
Structures of some monosaccharide alcohols
Must Know
Monosaccharide alcohols are very useful intermediates
Mannitol is used as an osmotic diuretic
Glycerol can be nitrated to nitroglycerin
Sorbitol can also be dehydrated to 1,4,3,6-dianhydro-D-sorbitol (isosorbide,) which can be further nitrated to isosorbide dinitrate (ISDN) and isosorbide monnitrate (ISMN ) both used in treatment of angina.
Must Know
Derivatives of Monosaccharaides
Monosaccharides can form various derivatives such as
Deoxy
Phosphate Ester
Amino Sugars
Derivatives of Monosaccharides
Must Know
Deoxy sugars: constituents of DNA, etc.
Deoxy Derivatives of Monosaccharides
Must Know
14
Sugar esters: phosphate esters like ATP are important
Phosphate Esters Derivatives of Monosaccharides
Must Know
Constituents of mucopolysaccharides
Amino: Derivatives of Monosaccharides
Must Know
Disaccharides
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Disaccharides
Several physiologically important disaccharides are sucrose (sugar cane, Glucose/Fructose), lactose (mammalian milk and formula, Galactose/Glucose) and maltose (in starch, Glucose/Glucose).
Disaccharides are formed by a covalent bond between two monosaccharide.
This is termed glycosidic bond.
Must Know
Lactose
Glucose + Galactose
Disaccharides
Condensation reaction
Must Know
O
CH
2
OH
O
O
CH
2
OH
SUCROSE
(glucose
-
fructose)
a
-
1,2
-
bond
OH
CH
2
OH
O
O
O
LACTOSE
(galactose
-
glucose)
b
-
1,4
-
bond
OH
OH
CH
2
OH
CH
2
OH
a vs b glycosidic linkage
1
2
1
4
We cannot metabolize this bond
We can metabolize this bond
Must Know
20
Carbohydrate Malabsorption
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Carbohydrate Malabsorption
Lactose intolerance (hypolactasia), Decline
lactase with age.
Lactose fermented in large intestine – Gas , Water retention – diarrhea/bloating
Not all populations
Northern European – low incidence
Asian/African Americans – High
b 1-4 linkage
Must Know
Lactose Intolerance
Inability to digest and absorb lactose due to shortage of enzyme lactase
At birth or late onset
Symptoms:
nausea
cramps
bloating
gas
diarrhea
Must Know
23
Causes:
10 lactase deficiency
20 lactase deficiency
Diagnosis
Lactose tolerance test
H2 breath test
Stool acidity test
Treatment
Lactase enzyme tablets/liquid
Consume smaller quantities
Low lactose products
Calcium and Vitamin D supplements
Lactose Intolerance
Must Know
24
Polysaccharides
25
• Polysaccharide – 100s – 1000s of monosaccharides
Two purposes:
Storage:
- plants – starch
- animals/Humans – glycogen
Structure:
- plants – cellulose (humans cannot metabolize it?)
- (animals – chitin)
Polysaccharides
Must Know
27
Complex Carbohydrates
Must Know
Animal storage - glycogen
Plant storage - starch
Polysaccharides - Storage
Must Know
28
29
Dietary Fiber
Indigestible chains of monosaccharides
Complex Carbohydrates
30
Complex Carbohydrates
Must Know
Digestion of Carbohydrates
31
Digestion of Carbohydrates
Early Digestion of Carbohydrates
Must Know
32
Digestion
Pre-stomach – Salivary amylase : a 1-4 endoglycosidase
G
G
G
G
G
G
G
G
a 1-4 link
G
G
G
G
a 1-6 link
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
maltose
G
G
G
isomaltose
amylase
maltotriose
G
G
G
G
a Limit dextrins
Must Know
33
Digestion of Carbohydrates
Must Know
34
Stomach
Not much carbohydrate digestion
Acid and pepsin to unfold proteins.
Must Know
Small Intestine
Pancreatic enzymes
a-amylase
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
amylose
amylopectin
G
G
G
G
G
a amylase
+
G
G
G
G
G
maltotriose
maltose
a Limit dextrins
G
Must Know
Brush Border Complexes
Digestion of Carbohydrates
Must Know
37
Oligosaccharide digestion..cont
G
G
G
G
G
G
G
G
G
G
G
G
Glucoamylase (maltase)
or
a-dextrinase
G
G
G
G
G
a-dextrinase
G
G
G
G
G
G
G
maltase
sucrase
a Limit dextrins
G
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Sugar
small intestine intestinal epithelial cell bloodstream
Only monosaccharides can be absorbed into intestinal epithelial cells, the rest go to the small intestine (lower part) to produce short chain fatty acids, lactate, H2 gas, methane, CO2 causes fluid secretion, increase intestinal motility and cramps.
Digestion of Carbohydrates
Must Know
Summary
Describe three classes of carbohydrates, how they are synthesized, specific examples of each (name, empirical and structural formulas) and their functions.
Describe digestion of Carbohydrates
Must Know
