Nutrient Absorption in Human Digestive System

Transportation of galactose is most rapid as it attaches with sodium ion and easily dragged by the protein carries so it is very easy to transport it while glucose and fructose require energy to transport as they are transported by active transport.

Active absorption occurs against the concentration gradient which requires energy. $Na^+$ which transports by facilitated transport that means it is taken by a protein carrier which has a peculiarity. It drags glucose with sodium ion from the lumen of the intestine to blood and helps in its absorption.

Absorption of nutrients and drugs is mainly carried out by the small intestine but the stomach also absorbs certain drugs, water, and alcohol while mouth absorbs a very little amount of water and drugs and breaks down starch.

• After food is being swallowed, from the mouth it is transported to the stomach. No absorption of nutrients takes place in the mouth and oesophagus. Hence, No absorption of food takes place in the mouth and oesophagus.
• Active glucose absorption is thought to depend on a gradient of sodium ion concentration across the brush border membrane of intestinal epithelial cells. Specifically, glucose absorption was minimally reduced when intraluminal sodium concentration was reduced. Hence, Absorption of glucose depends on sodium ion.
• Pinocytosis is the absorption of liquids, whereas phagocytosis is the absorption of solid objects which are essentially food for the cell. Phagocytosis engulfs whole particles, which are later broken down by enzymes, such as cathepsins, and absorbed into the cells. Hence, Whole protein particles cannot be engulfed by pinocytosis.

1. Brush bordered epithelium is microvilli covered Epithelial surface found in the body.
   2. The columnar and cuboidal epithelium of small intestine and PCT have the surface covered with microvilli for increasing absorption.
   3. Cilia are meant for the movement of fluid while microvilli function to increase the absorption and secretion.
   4. Microvilli are microscopic cellular membrane protrusions that increase the surface area for diffusion and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction.
   So, the correct option is 'Increase absorption of food.

Maximum absorption of water occurs in the large intestine, that is, in the colon. Certain drugs and metals are also absorbed here. 

 The absorption of digested carbohydrates, proteins and fats  is done in the small intestine with the help of villi which helps increase the surface area of the intestine. Villi are finger like projections on the intestinal wall that absorbs digested food material. Carbohydrates and proteins are absorbed into blood, while fats are absorbed into the lymph

The absorption is done in the small intestine with the help of villi which helps increase the surface area of the intestine, so as to store more digested food.

The correct answer is (a).

Diffusion is a process in which the molecules intermingle due to their kinetic energy and movement of molecules is from higher concentration to lower concentration. Osmosis is a process in which the water molecules move from lower solute concentration to higher solute concentration through a semi-permeable membrane. Digested food can pass into the blood vessels in the wall of the small intestine through the process of diffusion and water present in the ingested food is absorbed by the process of osmosis. 

The small intestine is meant for the reabsorption of water. Major absorption of water takes place in the intestine and further in the large intestine.

Intrinsic factors which are released by the stomach are used in the ileum of the small intestine for the absorption of vitamin $B _{12}$. These are majorly made up of glycoproteins.

Vitamin D helps in the absorption of calcium ion from the walls of the duodenum to the bloodstream and also maintains its level in the body.

Glucose and galactose transport against the concentration and hence require energy and carrier which transport them from lumen of the intestine to cell and are co transported with sodium ion.

Initiation of protein digestion starts in the stomach by pepsin but around 90-95% of protein is digested and absorbed in duodenum and jejunum of the small intestine in the form of amino acids by the action of enzymes trypsin, chymotrypsin and carboxypeptidases.

Water-soluble vitamins are directly absorbed into the intestine and transported to water as they do not require any emulsification because water is free to move in and out but fat soluble liquids absorb into lymph due to their insolubility in water and they need to emulsify before absorption.

• Absorption is the process by which the products of digestion are absorbed by the blood to be supplied to the rest of the body. 
• During absorption, the digested products are transported into the blood or lymph through the mucous membrane. Hence, Absorption is defined as the passage of nutrients from the gastrointestinal tract into the bloodstream.

Fructose and amino acids are absorbed in the small intestine via facilitated diffusion or secondary active transport, often coupled with Na+ ions. Option A is incorrect as salivary amylase hydrolyzes only about 30% of starch, and option B is incorrect because oxyntic cells secrete HCl.

Fatty acids and glycerol are insoluble in water and are incorporated into micelles, then resynthesized into chylomicrons. These chylomicrons are transported into the lacteals, which are lymphatic vessels located within the intestinal villi.

The primary function of the large intestine regarding absorption is the reabsorption of water and electrolytes, specifically the active transport of sodium ions from the lumen into the blood, which creates an osmotic gradient for water absorption.