AP BIOLOGY

Detailed explanation-1: -In our digestive system, most of the absorbtion and digestion take place in the small intestine but water, salts and minerals are only absorbed in the large intestine. Apart from that, the large intestine stores and removes undigested waste materials by expelling them through the anus.

Detailed explanation-2: -Absorption of Water and Electrolytes Sodium is actively absorbed in the colon by sodium channels. Potassium is either absorbed or secreted depending on the concentration in the lumen.

Detailed explanation-3: -The colon helps to absorb a small volume of water from the lumen (400ml/day). As the chyme is very concentrated by the time it reaches here, the colon must work against a larger osmotic pressure gradient than in the rest of the GIT. In other words, it must move water against the gradient for osmosis.

Detailed explanation-4: -Minerals can be absorbed from any portion of the GI tract. However, the bulk of absorption for most minerals takes place in the small intestine, so the general processes used for mineral absorption will be illustrated using the small intestine as the model.

Detailed explanation-5: -Absorption of ingested water and most solutes occurs in the proximal small intestine, therefore the rate at which beverages are emptied from the stomach is an important factor in determining the rate of water absorption.