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enzymes on the outer surface of the _____ _______ cleave common disaccharides
intestinal epithelium
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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.
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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.
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why is cellulose important for humans?
- Although mammals cannot digest
- cellulose and other plant fibers, soluble fibers, such as polygalacturonic
- acid, aid in digestion.
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what are the three classes of glycoproteins?
glycoproteins, proteoglycans, and mucins/mucoproteins
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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.
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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.
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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.
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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).
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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.
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what are Mucopolysaccahridoses?
Mucopolysaccahridoses, such as Huler’s disease, are pathological conditions that result from the inability to degrade proteoglycans.
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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.
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Proteoglycans are key components of the _______ _____ and serve as ________.
extracellular matrix, lubricants
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