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A Handbook of Biology

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They are reformed into small protein coated fat globules (chylomicrons).

[NEET 2013]

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They are transported into lacteals in the villi. From the lymph, the

chylomicrons enter the blood.

ÅBSØRPTÏØÑ ÏÑ DÏFFËRËÑT PÅRTS ØF ÅLÏMËÑTÅRÝ ÇÅÑÅL

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Mouth: Certain drugs.

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Stomach: Water, simple sugars, some drugs & alcohol.

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Small intestine: Almost all nutrients including minerals, vitamins etc.

Ileum is the chief area of absorption due to the presence of villi (it

increases surface area of absorption), its great length and coiled nature.

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Large intestine: Water, some minerals & drugs. The absorbed materials

are incorporated into tissues for their activities. It is called assimilation.

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The undigested substances like plant fibres, dead bacteria etc. form

faeces. It enters caecum through the ileo-caecal valve, which prevents

back flow of faeces.

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Faeces are temporarily stored in rectum and are eliminated through

anus. It is called egestion (defaecation).

ÇÅLØRÏFÏÇ VÅLÜË ØF PRØTËÏÑ, ÇÅRBØHÝDRÅTË ÅÑD FÅT (ÑØT FØR

ËVÅLÜÅTÏØÑ)

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One calorie is the amount of heat energy required to raise the

temperature of 1g of water by 1°C.

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This value is tiny amount of energy. So physiologists use kilocalorie (kcal

or Cal) or kilo joule (kJ or Joule).

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One kilo calorie is the amount of energy required to raise the temperature

of 1kg of water by 1°C.

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Amount of heat liberated from complete combustion of 1g food in a

bomb calorimeter (a closed metal chamber filled with O2) is its gross

calorific (gross energy) value.

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Actual amount of energy combustion of 1g of food is the physiologic

value of food.

Gross calorific value

Physiologic value

Carbohydrates

4.1 kcal/g

4.0 kcal/g

Proteins

5.65 kcal/g

4.0 kcal/g

Fats

9.45 kcal/g

9.0 kcal/g