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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