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Pepsin / ˈ p ɛ p s ɪ n / is an endopeptidase that breaks down proteins into smaller peptides and amino acids. It is one of the main digestive enzymes in the digestive systems of humans and many other animals, where it helps digest the proteins in food. Pepsin is an aspartic protease, using a catalytic aspartate in its active site. [2]
Chronic inflammatory diseases such as rheumatoid arthritis may involve the release of lysosomal enzymes into extracellular space that break down surrounding tissues. Abnormal proteolysis may result in age-related neurological diseases such as Alzheimer 's due to the generation and ineffective removal of peptides that aggregate in cells.
Protein catabolism often begins with pepsin, which converts proteins into polypeptides. These polypeptides are then further degraded. In humans, the pancreatic proteases include trypsin, chymotrypsin, and other enzymes. In the intestine, the small peptides are broken down into amino acids that can be absorbed into the bloodstream.
Water splitting is the chemical reaction in which water is broken down into oxygen and hydrogen: [1] 2 H 2 O → 2 H 2 + O 2 Efficient and economical water splitting would be a technological breakthrough that could underpin a hydrogen economy .
Once in the more neutral duodenum, pancreatic enzymes break down the protective glycoprotein. The freed vitamin B12 then binds to intrinsic factor which is then absorbed by the enterocytes in the ileum. The stomach is a distensible organ and can normally expand to hold about one litre of food. [22]
This type of cell also secretes gastric lipase enzymes, which help digest triglycerides into free fatty acids and di- and mono-glycerides. [6] There is also evidence that the gastric chief cell secretes leptin in response to the presence of food in the stomach. Leptin has been found in the pepsinogen granules of chief cells. [7]
Absorbed amino acids are typically used to create functional proteins, but may also be used to create energy. [3] They can also be converted into glucose. [4] This glucose can then be converted to triglycerides and stored in fat cells. [5] Proteins can be broken down by enzymes known as peptidases or can break down as a result of denaturation ...
The rest of the amino acid is made up of mostly carbon and hydrogen, and is recycled or oxidized for energy. Ammonia is toxic to the human system, and enzymes convert it to urea or uric acid by addition of carbon dioxide molecules (which is not considered a deamination process) in the urea cycle , which also takes place in the liver.