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enzymes on the outer surface of the _____ _______ cleave common disaccharides
name some enzymes on the intestinal epithelium that break down disaccharides
- Sucrase cleaves sucrose (table sugar),
- lactase cleaves lactose (milk sugar), and maltase cleaves maltose.
describe the structure of cellulose
Cellulose is a homopolymer of glucose units linked by β-1, 4-glycocidic bond. The β linkage yields a straight chain capable of interacting with other cellulose molecules to from strong fibrils.
why is cellulose important for humans?
- Although mammals cannot digest
- cellulose and other plant fibers, soluble fibers, such as polygalacturonic
- acid, aid in digestion.
what are the three classes of glycoproteins?
glycoproteins, proteoglycans, and mucins/mucoproteins
what are glycoproteins?
A carbohydrate attached to a protein. The protein is the largest component by weight. Glycoproteins play a variety of roles including as membrane proteins.
what are proteoglycans?
The protein is attached to a particular type of polysaccharide called a glycosaminoglycan. By weight, proteoglycans are mainly carbohydrate. Proteoglycans play structural roles or act as lubricants.
what are mucins/mucoproteins?
Like proteoglycans, mucins are predominantly carbohydrate. The protein is characteristically attached to the carbohydrate by N-acetylgalactosamine. Mucins are often lubricants.
carbohydrates may be linked to which amino acid residues?
In all classes of glycoproteins, carbohydrates are attached to the nitrogen atom in the side chain of asparagine (N-linkage) or to the oxygen atom of the side chain of serine or threonine (O-linkage).
what do all N-linked polysaccharides have in common?
All N-linked polysaccharides consist of a common pentasaccharide core, consisting of three mannoses, a six-carbon sugar, and two N-acetylgalactosamine units.
Additional monosaccharides may be attached to the core.
what are Mucopolysaccahridoses?
Mucopolysaccahridoses, such as Huler’s disease, are pathological conditions that result from the inability to degrade proteoglycans.
what are glycosaminoglycans?
Glycosaminoglycans are composed of repeating units of a disaccharide, one of which is a derivative of an amino sugar and one of which carries a negative charge, either as a carboxylate or sulfate.
Proteoglycans are key components of the _______ _____ and serve as ________.
extracellular matrix, lubricants