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The seven major classes of nutrients are carbohydrates, fats, fiber, minerals, proteins, vitamins, and water. [7] Nutrients can be grouped as either macronutrients or micronutrients (needed in small quantities). Carbohydrates, fats, and proteins are macronutrients, and provide energy. [7]
Aside from water, proteins are the most abundant kind of molecules in the body. Protein can be found in all cells of the body and is the major structural component of all cells in the body, especially muscle. This also includes body organs, hair and skin. Proteins are also used in membranes, such as glycoproteins.
In molecular biology, protein catabolism is the breakdown of proteins into smaller peptides and ultimately into amino acids. Protein catabolism is a key function of digestion process. Protein catabolism often begins with pepsin, which converts proteins into polypeptides. These polypeptides are then further degraded.
Trypsin is an enzyme in the first section of the small intestine that starts the digestion of protein molecules by cutting long chains of amino acids into smaller pieces. It is a serine protease from the PA clan superfamily, found in the digestive system of many vertebrates, where it hydrolyzes proteins.
The liver is the second largest organ (after the skin) and is an accessory digestive gland which plays a role in the body's metabolism. The liver has many functions some of which are important to digestion. The liver can detoxify various metabolites; synthesise proteins and produce biochemicals needed for digestion.
It is the most abundant protein in mammals, [1] making up 25% to 35% of protein content. Amino acids are bound together to form a triple helix of elongated fibril [ 2 ] known as a collagen helix . It is mostly found in cartilage , bones , tendons , ligaments , and skin .
Proteins may be classified as to their three-dimensional structure (also known a protein fold). The two most widely used classification schemes are: [2] CATH database [3] Structural Classification of Proteins database (SCOP) [4] Both classification schemes are based on a hierarchy of fold types.
Through digestion, proteins are broken down by proteases back into free amino acids. Fats consist of a glycerin molecule with three fatty acids attached. Fatty acid molecules contain a -COOH group attached to unbranched hydrocarbon chains connected by single bonds alone ( saturated fatty acids ) or by both double and single bonds ( unsaturated ...