Question

How does the food you eat change the absorption rate and quality of absorption of the small and large intestines? Explore cooking, temperature, parts of the food items ingested........CHEMISTRY!!! How might this info be used to keep your weight up? Down? Maintained????

Answer 1

The pancreas and gland cells of the small intestine secrete digestive enzymes that chemically break down complex food molecules into simpler ones. ... The increased contact causes more efficient food absorption. During food absorption, food molecules enter the bloodstream through the intestinal walls.

Carbohydrate Absorption

All normally digested dietary carbohydrates are absorbed; indigestible fibers are eliminated in the feces. The monosaccharides glucose and galactose are transported into the epithelial cells by common protein carriers via secondary active transport (that is, co-transport with sodium ions). The monosaccharides leave these cells via facilitated diffusion and enter the capillaries through intercellular clefts. The monosaccharide fructose (which is in fruit) is absorbed and transported by facilitated diffusion alone. The monosaccharides combine with the transport proteins immediately after the disaccharides are broken down.

Protein Absorption

Active transport mechanisms, primarily in the duodenum and jejunum, absorb most proteins as their breakdown products, amino acids. Almost all (95 to 98 percent) protein is digested and absorbed in the small intestine. The type of carrier that transports an amino acid varies. Most carriers are linked to the active transport of sodium. Short chains of two amino acids (dipeptides) or three amino acids (tripeptides) are also transported actively. However, after they enter the absorptive epithelial cells, they are broken down into their amino acids before leaving the cell and entering the capillary blood via diffusion.

Lipid Absorption

About 95 percent of lipids are absorbed in the small intestine. Bile salts not only speed up lipid digestion, they are also essential to the absorption of the end products of lipid digestion. Short-chain fatty acids are relatively water soluble and can enter the absorptive cells (enterocytes) directly. Despite being hydrophobic, the small size of short-chain fatty acids enables them to be absorbed by enterocytes via simple diffusion, and then take the same path as monosaccharides and amino acids into the blood capillary of a villus.

The large and hydrophobic long-chain fatty acids and monoacylglycerides are not so easily suspended in the watery intestinal chyme. However, bile salts and lecithin resolve this issue by enclosing them in a micelle, which is a tiny sphere with polar (hydrophilic) ends facing the watery environment and hydrophobic tails turned to the interior, creating a receptive environment for the long-chain fatty acids. The core also includes cholesterol and fat-soluble vitamins. Without micelles, lipids would sit on the surface of chyme and never come in contact with the absorptive surfaces of the epithelial cells. Micelles can easily squeeze between microvilli and get very near the luminal cell surface. At this point, lipid substances exit the micelle and are absorbed via simple diffusion.

Nucleic Acid Absorption

The products of nucleic acid digestion—pentose sugars, nitrogenous bases, and phosphate ions—are transported by carriers across the villus epithelium via active transport. These products then enter the bloodstream.

Mineral Absorption

Iron—The ionic iron needed for the production of hemoglobin is absorbed into mucosal cells via active transport. Once inside mucosal cells, ionic iron binds to the protein ferritin, creating iron-ferritin complexes that store iron until needed. When the body has enough iron, most of the stored iron is lost when worn-out epithelial cells slough off. When the body needs iron because, for example, it is lost during acute or chronic bleeding, there is increased uptake of iron from the intestine and accelerated release of iron into the bloodstream. Since women experience significant iron loss during menstruation, they have around four times as many iron transport proteins in their intestinal epithelial cells as do men.

Calcium—Blood levels of ionic calcium determine the absorption of dietary calcium. When blood levels of ionic calcium drop, parathyroid hormone (PTH) secreted by the parathyroid glands stimulates the release of calcium ions from bone matrices and increases the reabsorption of calcium by the kidneys. PTH also upregulates the activation of vitamin D in the kidney, which then facilitates intestinal calcium ion absorption.

Vitamin Absorption

The small intestine absorbs the vitamins that occur naturally in food and supplements. Fat-soluble vitamins (A, D, E, and K) are absorbed along with dietary lipids in micelles via simple diffusion. This is why you are advised to eat some fatty foods when you take fat-soluble vitamin supplements. Most water-soluble vitamins (including most B vitamins and vitamin C) also are absorbed by simple diffusion. An exception is vitamin B₁₂, which is a very large molecule. Intrinsic factor secreted in the stomach binds to vitamin B₁₂, preventing its digestion and creating a complex that binds to mucosal receptors in the terminal ileum, where it is taken up by endocytosis.

A Food is Not a Food—Estimates of the number of calories in different kinds of foods measure the average number of calories we could get from those foods based only on the proportions of fat, carbohydrates, protein and sometimes fiber they contain (In essence, calories ingested minus calories egested). A variety of standard systems exist, all of which derive from the original developed by Wilbur Atwater more than a hundred years ago. They are all systems of averages. No food is average.

Differences exist even within a given kind of food. Take, for example, cooked vegetables. Cell walls in some plants are tougher to break down than those in others; nature, of course, varies in everything. If the plant material we eat has more of its cell walls broken down we can more of the calories from the goodies inside. In some plants, cooking ruptures most cell walls; in others, such as cassava, cell walls hold strong and hoard their precious calories in such a way that many of them pass through our bodies intact.

It is not just cooked vegetables though. Nuts flagrantly do their own thing, which might be expected given that nuts are really seeds whose mothers are invested in having them escape digestion. Peanuts, pistachios and almonds all seem to be less completely digested than their levels of protein, fat, carbohydrates and fiber would suggest. How much? Just this month, a new study by Janet Novotny and colleagues at the USDA found that when the “average” person eats almonds she receives just 128 calories per serving rather than the 170 calories “on the label.”

Hence rate of absorption depends on the food we eat , as the food contains macro and micro molecule.

and hence if the rate of absorption also has a significant role in the weight . if there is a good rate of absorption then weight will be maintained but if there is fluctuation as in very increase rate will lead to decrease in weight and very lower rate will lead to increase in weight .

. Mechanical digestion includes chewing and swallowing . Chemical digestion of carbohydrates, fats Mechanical digestion includes peristaltic mixing and propulsion Esophagus . Chemical digestion of proteins, fats Absorption of lipid-soluble substances such as alcohol and aspirin Liver Gallbladder Pylorus Pancreas Mechanical digestion includes mixing and propulsion, primarily by segmentation . Chemical digestion of carbohydrates, fats, polypeptides, nucleic acids Absorption of peptides, amino acids, glucose, fructose, fats, water, minerals, and vitamins . Mechanical digestion includes segmental mixing and propulsion No chemical digestion (except by bacteria) Absorption of ions, water, Rectum minerals, vitamins, and organic molecules Anal sphincter

Starch Glycogen ← Salivary amylase Disaccharides Maltose Sucrose Lactose Maltase Sucrase Lactase Monosaccharides 2 glucose 1 glucose 1 fructose 1 glucose 1 galactose

Dietary input Food and drink 2000 mL Digestive secretions Saliva 1500 mL Gastric secretions 1500 mL 5000 mL Liver (bile) 1000 mL Pancreas (pancreatic juice) 1000 mL Intestinal secretions 9000 mL Water reabsorption 2000 mL Small intestine reabsorb:s 7800 mL 1200 mL Colonic mucous secretions 200 mL 1400 mL Colon reabsorb:s 1250 mL -150 mL lost in feces