Carbohydrate
Aulanni’amLaboratory of BiochemistryBrawijaya University
Six Classes of Nutrients
1. Carbohydrate2. Protein3. Fat4. Vitamins 5. Minerals 6. Water
Carbohydrates and Relation to Health
1. Dietary fiber and prevention of chronic diseases2. Carbohydrates and dental health3. Carbohydrates and diabetes
Carbohydrates and weight loss???
1. Carbohydrates and Prevention of Chronic DiseasesHealth 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 CarbohydratesStarch
digestible plant polysaccharide
Fiberindigestible 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 SourcesSoluble Fiber - Heart Insoluble Fiber – GI tract
● Oatmeal
● Nuts and seeds
● Legumes • dried peas • beans
● Fruits • apples • pears
● Whole grains
● Wheat bran
● Vegetables• carrots• celery
Degree of polymerization
• Monosaccharides• Storage, energy modules, metabolic intermediates
• Disaccharides, trisaccharides • Storage
• Oligosaccharides• Molecular Recognition
• Polysaccharides • Structure, storage
Fisher Projectionsof chiral monosaccharides
• Next-to-bottom carbon hydroxyl extends to the right --- a D sugar; cf. with L amino acid
CHO
CH2OH
OHH
D-glyceraldehyde
CH3
NH2 H
COOH
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
CHO
CH2OH
OHH
HOH
OHH
OHH
O OH
OH
OH
OH
OH
O
OH
HH
H
OH
OH
H OH
H
OH
O
OHOH
HH
H
H
HOHOH
OH
open chain
stereo
Haworth
chair
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 –(nm)-
• Reducing endNote 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 (-D-glucopyranosyl-(14)-…), 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 HealthDental Caries (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)
CavitiesBacterial + Sugars
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
5-10% of casesPancreas unable to make
insulin to meet needs
Genetic predisposition + environmental factors
Insulin injections Dietary Intervention• Reduce the amount of simple
sugars • Eat foods w/ dietary fiber Person will lose weight
90-95% of casesMaybe insufficient insulin or cells
maybe unresponsive to insulinGenetic predisposition + obesity
Dietary intervention
Weight loss intervention
Person is always hungryIncrease in obesity
IncidenceInsulin
Risk factor
Treatment
Type 1 – Insulin DependentType 2 – Non- Insulin Dependent
Carbohydrates role in blood glucose
• A numerical system
• Measures extent of rise in circulating blood sugar a carbohydrate triggers
• GI number, blood sugar response
Glycemic Index
Glycemic Index estimate of how quickly food affects your blood sugar
Glycemic Index
High GI > 70 potatoes, white bread Low GI < 55 pasta, whole grain bread
Not just about individual foodsit’s about our diet
Factors Influencing GI
1. Biochemical structure of the carbohydrate2. Absorption process3. Size of the food particle4. Contents and timing of the previous meal5. Co-ingestion of fat, fiber, or protein
Carbohydrates and Weight Loss??• Low carb diets• ‘Diet’ and low calorie foods
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