Transcript Polysaccharide

Carbohydrate
Aulanni’am
Laboratory of Biochemistry
Brawijaya University
Six Classes of Nutrients
1.
2.
3.
4.
5.
6.
Carbohydrate
Protein
Fat
Vitamins
Minerals
Water
Carbohydrates and Relation to
Health
1. Dietary fiber and prevention of chronic diseases
2. Carbohydrates and dental health
3. Carbohydrates and diabetes
Carbohydrates and weight loss???
1.
Carbohydrates and Prevention of Chronic Diseases
Health Benefits of Fiber
Reduce the risk of
• Heart disease
• Diabetes
• Diverticular disease (gastrointestinal / GI)
Other
• Relieves Constipation
• Hemorrhoids
• Lowers the GI/GL
• Makes you feel full
Complex Carbohydrates
Starch
digestible plant polysaccharide
Fiber
indigestible polysaccharide residues of food
• Cannot be broken down by human digestive enzymes
• some broken down by bacteria in the digestive tract
• few, if any, calories because not digested
• Examples: cellulose, hemicellulose, pectin, gums
Polysaccharide: long chain of 10 or more glucose molecules linked together; the
chains can be straight or branched; another term for complex carbohydrates
Dietary Fiber
• Components of the cell walls of plants
• cereal grains, fruits, vegetables
• Polymer of monosaccharides
• Human digestive enzymes cannot break down
• Cellulose = ~3000 glucose
Dietary Fiber - Two groups
1. Insoluble
•
•
fibers that mostly do not dissolve in water
not digested by bacteria in the large intestine
2. Soluble
•
•
fibers that either dissolve or swell in water or
are metabolized by bacteria in the large intestines
Fiber Sources
Soluble Fiber - Heart
Insoluble Fiber – GI tract
● Oatmeal
● Whole grains
● Nuts and seeds
● Wheat bran
● Legumes
• dried peas
• beans
● Vegetables
● Fruits
• apples
• pears
•
•
carrots
celery
Degree of polymerization
• Monosaccharides
• Storage, energy modules, metabolic intermediates
• Disaccharides, trisaccharides
• Storage
• Oligosaccharides
• Molecular Recognition
• Polysaccharides
• Structure, storage
Fisher Projections
of chiral monosaccharides
• Next-to-bottom carbon hydroxyl extends to the right --- a D
sugar; cf. with L amino acid
CHO
H
OH
CH 2OH
D-glyceraldehyde
COOH
H2N
H
CH3
L-valine
fig 9-3a
fig 9-3b
Hemiacetal/-ketal structures of
monosaccharides
• Reaction of an aldehyde or ketone with an alcohol
• favorable intramolecular reaction
fig 9-5
Intramolecular hemiacetals/ketals of
monosaccharides are RINGS
OH
O
HO
stereo
CHO
H
HO
H
H
HO
OH
OH
OH
H
OH
OH
OH
CH 2OH
open chain
O H
H
H
H
OH
H
HO
OH
H
O
HO
HO
H
OH
Haworth
chair
OH
H
H
H
OH
OH
Anomers
• Sugars that vary in configuration about the anomeric
(aldehydic or ketonic) carbon
• Convention:  = hydroxyl down,
 = hydroxyl up
fig 9-6
Fig 9-7
Hexose derivatives
• Amino sugars
• Acetamido sugars
• Deoxy sugars
• Fucose, rhamnose, abequose
• Other glycosidic additives
• Lactic acid
• Oxidized sugars
• Sugar phosphates
Fig 9-9
Reducing sugars
• Aldehydes are oxidized by mild agents
• Cu2+ + aldehyde (or -hydroxyketone)  Cu+ + acid
• Disaccharides react more slowly
Fig 9-10
Disaccharides
• Glycosidic linkage
• Acetal (or ketal) formed. 2nd monosaccharide acts as an alcohol
Fig 9-5 (repeat)
• Reducing
• one anomeric C not glycosidically linked
• Nonreducing
• Both anomeric C’s linked (fructose, trehalose)
Disaccharide nomenclature
• Nonreducing end on left
• Linkage –(nm)• Reducing end
Note that nonreducing end configuration is fixed
Reducing end can mutarotate, thus 1st component given as - or -, 2nd
ambiguous (next slide)
Fig 9-11
Table 9-1
Important disaccharides
•
•
•
•
Maltose
Lactose
Sucrose
Trehalose
Fig 9-12
Table 9-2
Storage polysaccharides
• Plants
• Starch
• Amylose – llinear polyglucose, -1,4 linked (-Dglucopyranosyl-(14)-…), M ~ 106
• Amylopectin –polyglucose, -1,4 linked, -1,6 branched 1 per
24-30, M ~ 108
• Animals
• Glycogen
• polyglucose, -1,4 linked, -1,6 branched 1 per 24-30, M ~
106
Fig 9-15 b
Fig 9-14
1.0 m
0.10 m
fig 9-15
Structural Polysaccharides
• Plants
• Cellulose – linear polyglucose
•  1,4 linked
• M ~ 106
• Certain exoskeletons
• Chitin – linear poly(N-acetyl-D-glucosamine)
•  1,4 linked
Fig 9-17a and 9-18
Cellulose
Chitin
Structural polysaccharides, cont
• Bacterial cell walls – peptidoglycans
• Extracellular matrix of multicellular animals glycosaminoglycans
Fig 9-19
Fig 9-20
Sugar-protein and sugar-lipid
conjugates
• Glycoconjugates
• Proteoglycans
• Glycosaminoglycans bound to proteins
• Glycoproteins
• Oligosaccharides bound to proteins
• Glycolipids
• Oligosaccharides bound to lipids (heads of membrane lipids)
Fig 9-29
Fig 9-27
2. Carbohydrates and Dental
Health
Dental Caries (Cavities)
Bacterial + Sugars
Cavities
MECHANISM
• Bacterial acid dissolves enamel
• Carbohydrate serves as food for bacteria
• Plaque on teeth – sugars stay in but acids don’t go out
CARIOGENIC FOOD FACTORS
• Fermentable – contains sugars
• Sticky
• Stays in mouth a long time (think taffy)
3. Carbohydrates and Diabetes
Diabetes: An inability to regulate blood glucose levels
• A disease in which an individual does not produce or properly use insulin
Results in:
• abnormally high levels of glucose in blood
Because of:
• lack or ineffectiveness of insulin
 hormone that is needed to convert sugar, starches and other food
into energy needed for daily life
the true cause continues to be a mystery,
although both genetics and environmental factors
such as obesity and lack of exercise play roles
Type I vs. Type II Diabetes
Type 1 – Insulin Dependent
Type 2 – Non- Insulin Depend
Incidence
Insulin
5-10% of cases
Pancreas unable to make
insulin to meet needs
Risk factor
Genetic predisposition +
environmental factors
90-95% of cases
Maybe insufficient insulin or cells
maybe unresponsive to insulin
Genetic predisposition + obesity
Dietary intervention
Weight loss intervention
Treatment
Insulin injections
Dietary Intervention
• Reduce the amount of simple
sugars
• Eat foods w/ dietary fiber
Person will lose weight
Person is always hungry
Increase in obesity
Carbohydrates role in blood
glucose
Glycemic Index
• A numerical system
• Measures extent of rise in circulating blood sugar a carbohydrate
triggers
•
GI number,
blood sugar response
Glycemic Index
estimate of how quickly food affects your blood sugar
Glycemic Index
High GI
Low GI
> 70
< 55
potatoes, white bread
pasta, whole grain bread
Not just about individual foods
it’s about our diet
Factors Influencing GI
1.
2.
3.
4.
5.
Biochemical structure of the carbohydrate
Absorption process
Size of the food particle
Contents and timing of the previous meal
Co-ingestion of fat, fiber, or protein
Carbohydrates and Weight
Loss??
• Low carb diets
• ‘Diet’ and low calorie foods
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