Digestion is the chemical or mechanical breakdown of the product into such small molecules that they can be absorbed by the cells of the small intestine.
Fat-breaking enzymes are lipases, proteins are proteases and carbohydrates are amylases.
There is a proverb that digestion begins even before eating, because the thought, smell or sight of food arouses, for example, salivary diarrhea.
Digestion begins with the oral cavity. Salivary secreted by the salivary glands, which contains salivary amylase and salivary lipase.
Salivary Amylase breaks the long chains of sugars into a shorter, while salivary lipase only affects milk fat and this is the minimum effect due to the exposure time of the enzyme to the substrate.
The mouth also comes to mechanical digestion by chewing food. This process allows easier access of enzymes to substrates in further parts of the digestion.
The food passes through the esophagus and goes to the stomach. The stomach is mainly digested proteins, despite the fact that there is a stomach lipase, its effect on the digestion of fats is really not great, because lipases work in alkaline environments, and in the stomach is strongly acidic (only in young children stomach ph 6.0 and the beginning of digestion of fats starts right here).
Let’s get to the proteins. In the stomach, the polypeptide chains are broken down into shorter chains, then the peristaltic contractions of the stomach are moved further to the small intestine. There, proteases break down proteins into tri and dipeptides (a tripeptide is a combination of 3 amino acids, and d and 2, etc.) and subsequently into single amino acids. Finally, the amino acids are absorbed by the villi of the small intestine into the circulatory system.
While returning to fat; the main role in their digestion is played by pancreatic lipase secreted into the small intestine. Lipase breaks down fats into glycerols and fatty acids so that they are sequentially absorbed by the villi of the intestine and then into the lymphatic system.
Carbohydrates, as it was written at the beginning, the process of digesting them begins in the oral cavity, then goes into the small intestine and under the influence of amylases breaks down to disaccharides and then, depending on the substrate (eg sucrose, maltose) by appropriate enzymes (e.g. . saccharase, maltase) to glucose – the simplest sugar. The final effect is that glucose is absorbed in the villi of the small intestine and absorbed into the circulatory system.
Digestion also takes place in the colon, it is anaerobic digestion with the help of bacteria. The by-products are toxic and neurotoxic. They cause discomforts from the parts of the digestive system (eg diarrhea) and are most often caused by too large amounts of protein. In the large intestine there is the formation of faeces and absorption of water and vitamins produced by the bacterial flora.
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