CARBOHYDRATE METABOLISM

1/3 of body’s glycogen is stored in liver released as glucose to bloodstream

1. eat – intake glucose2. liver condenses extra glucose to glycogen3. blood glucose falls4. liver hydrolyzes glycogen to glucose

Glycogen is bulky, so we store only so much: short term energy supply

Fat is the long term energy supply.

CARBOHYDRATES

CARBOHYRATES OCCURENCE

EFFICIENT ENERGY:NECESSARY NUTRIENT

CARBOHYDRATES COMPOSITION

A carbohydrate is an organic compound comprising only carbon, hydrogen, and oxygen, usually with a hydrogen : oxygen atom ratio of 2:1 (as in water); in other words, with the empirical formula Cm(H2O)n 

CARBOHYDRATES CLASSIFICATIONS

SIMPLE CARBOHYDRATES

SIMPLE(sugars)

COMPLEX CARBOHYDRATES

COMPLEX(polysaccharidesStarch/Fiber)

CLASSIFICATION

SIMPLE COMPOUND

MONOSACCHARIDES GLUCOSE FRUCTOSE GALACTOSE

OLIGOSACCRIDES Glucose +Fructose +Galactose =RAFFINOSE Two alpha D-galactose = STACHYOSE

DISACCHARIDES Glucose + Fructose = SUCROSE Galactose+ glucose = LACTOSE Glucose +glucose = MALTOSE

POLYSACCHARIDES Large no. Of glucose + join + glycosidic bond= STARCH

CLASSIFICATION OF CARBOHYDRATES

Monosaccharides- glucose, fructose,galactose Oligosaccharides

Di, tri, tetra, penta, up to 9 or 10 Most important are the disaccharides-lactose,

sucrose,maltose Polysaccharides or glycans

Homopolysaccharides-starch, glycogen, cellulose Heteropolysaccharides

STRUCTURE OF TYPES OF CARBOHYDRATES

oligosaccharides

SIMPLE CARBOHYDRATES

1. MONOSACCHARIDES

GLUCOSE FRUCTOSE GALACTOSE

Monosaccharidesall are 6 carbon hexes6 carbons12 hydrogens6 oxygensarrangement differsaccounts for varying sweetnessglucose, fructose, galactose

GLUCOSE mild sweet flavor known as blood sugar essential energy source found in every disaccharide

and polysaccharide

FRUCTOSE sweetest sugar found in fruits and honey added to soft drinks, cereals,

deserts

GALACTOSE hardly tastes sweet rarely found naturally

as a single sugar

2. DISACCHARIDES

DISACCHARIDES pairs of the monosaccharides

glucose is always present 2nd of the pair could be fructose, galactose or another

glucose taken apart by hydrolysis put together by condensation hydrolysis and condensation occur with all energy

nutrients maltose, sucrose, lactose

CONDENSATION

making a disaccharidechemical reaction linking

2 monosaccharides

MALTOSE 2 glucose units produced when starch breaks down not abundant

SUCROSE

fructose and glucose tastes sweet

fruit, vegetables, grains table sugar is refined

sugarcane and sugar beets

brown, white, powdered

LACTOSE

glucose and galactose

main carbohydrate in milkknown as milk

sugar

COMPOUND CARBOHYDRATES

1. OLIGOSACCHARIDES

RAFFINOSE STACHYOSE

2.POLYSACCHARIDES

STARCH

CELLULOSE

GLYCOGEN

POLYSACCHARIDES(COMPLEX CARBOHYDRATES)

homoglycans (starch, cellulose, glycogen, inulin)

heteroglycans (gums, mucopolysaccharides)

characteristics: polymers (MW from 200,000) White and amorphous products (glassy) not sweet not reducing; do not give the typical aldose or ketose

reactions) form colloidal solutions or suspensions

STARCH most common storage polysaccharide in plants composed of 10 – 30% -a amylose and 70-90%

amylopectin depending on the source Common sources are grains , potatoes, peas,

beans, wheat

GLYCOGEN also known as animal starch stored in muscle and liver present in cells as granules (high MW) contains both a(1,4) links and a(1,6)

branches at every 8 to 12 glucose unit complete hydrolysis yields glucose

FIBERS Found in food derived from plants Includes polysaccharides such as cellulose,

hemicellulose, pectins, gums and mucilages Also includes non-polysaccharides such as

lignin, cutins and tannins Fibers are not a source of energy because

Human digestive enzymes cannot break down fibers

The bacteria in human GI tract can breakdown some fibers.

way of classifying food according to their ability to raise blood glucose

much controversy

GLYCEMIC INDEX

Glycemic index is defined as the area under the blood glucose curves seen after ingestion of a meal with carbohydrate-rich food, compared with the area under the blood glucose curve observed after a meal consisting of the same amount of carbohydrate in the form of glucose or white bread.

REQUIREMENTS FOR CARBOHYDRATE

The RDA for carbohydrate is set at 130 g/day for adults and children, based on the amount of glucose used by carbohydrate-dependent tissues, such as the brain and erythrocytes.

Adults should consume 45–65 percent of their total calories from carbohydrates.

It is recommended that added sugar represent no more than 25% of total energy because of concerns that sugar may displace nutrient-rich foods from the diet, potentially leading to deficiencies of certain micronutrients.

PROPERTIES

1. MONOSACCHARIDE - These are crystalline compounds, soluble in water, sweet to taste, and needsdigestion in order to be absorbed into the blood stream. They may contain either five carbons (pentose)or six carbons (hexose).2. DISACCHARIDES -These are crystalline, water-soluble, sweet to the taste, and must be digested tomonosaccharides before they can be absorbed and used for energy. These are a combination of twomonosaccharides.3. POLYSACCHARIDES -These are not water soluble and are not crystalline. They form colloidalsuspensions instead of solutions. They are not sweet and must be digested before being absorbed.They are made up of many polysaccharides joined together.The water solubility obviously depended on the molecular weight of carbohydrates in water.

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