Polysaccharides Flashcards
what are polysaccharides also called
glycans
Some Homopolysaccharides Are Stored Forms of ____
Fuel
why are starch and glycogen heavily hydrated
because they have many exposed hydroxyl groups available to hydrogen-bond with water
what does amylose and amylopectin contain
amylose consists of long, unbranched chains of D-glucose residues connected by (α1→4) linkages and Amylopectin has glycosidic linkages joining successive glucose residues (α1→4); the branch points are (α1→6) linkages
describe the structure of glycogen
is a polymer of (α1→4) -linked subunits of glucose, with (α1→6) -linked branches
what is more branched and compact, starch or glycgen
glycogen
where is glycogen in the body
abundant in the liver, it is also present in skeletal muscle
glycogen molecule has as many__________ ends as it has branches, but only one ________ end
nonreducing
reducing
how is glycogen broken down as an energy source
glucose units are removed one at a time from the nonreducing ends
how are starch and glycogen ingested in the diet
hydrolyzed by α-amylases, enzymes in saliva and intestinal secretions that break (α1→4) glycosidic bonds between glucose units
what is the structure of cellulose
linear, unbranched homopolysaccharide, consisting of 10,000 to 15,000 D-glucose units
how are the glucose residues in cellulose linked
by (β1→4) glycosidic bonds
This difference gives cellulose and amylose very different structures and physical properties
what is the structure of chitin
linear homopolysaccharide composed of N-acetylglucosamine residues in β linkage
what is the chemical difference between cellulose and chitin
replacement of the hydroxyl group at C-2 with an acetylated amino group in chitin
what is the rigid component of bacterial cell walls
heteropolymer of alternating (β1→4)-linked N-acetylglucosamine and N-acetylmuramic acid residues
how does lysozyme kill bacteria
by hydrolyzing the (β1→4) glycosidic bond between N-acetylglucosamine and N-acetylmuramic acid
Lysozyme is notably present in ______, presumably as a defense against bacterial infections of the_____
tears
eye
how do penicillin and other antibiotics kill bacteria
by preventing synthesis of the cross-links, leaving the cell wall too weak to resist osmotic lysis
what are glycosaminoglycans
heteropolysaccharides of linear polymers composed of repeating disaccharide units
what are the are the two monosaccharides contained in glycosaminoglycans
- either N-acetylglucosamine or N-acetylgalactosamine
* other is in most cases a uronic acid, usually D-glucuronic or L-iduronic acid
In some glycosaminoglycans what are the hydroxyls of the amino sugar esterified with
sulfate
what forms proteoglycans
Glycosaminoglycans attached to extracellular proteins
what is hyaluronic acid
a glycosaminoglycan containing alternating residues of D-glucuronic acid and N-acetylglucosamine
what is the functions of hyaluronic acid
serve as lubricants in the synovial fluid of joints and give the vitreous humor of the vertebrate eye its jelly like consistency
also in extracellular matrix of cartilage and tendons for tensile strength
what secretes Hyaluronidase and what does it do
it is an enzyme secreted by some pathogenic bacteria and it can hydrolyze the glycosidic linkages of hyaluronate, rendering tissues more susceptible to bacterial invasion
a similar enzyme to Hyaluronidase in sperm hydrolyzes ____________
an outer glycosaminoglycan coat around the ovum, allowing sperm penetration
how do other glycosaminoglycans differ from hyaluronate
they are generally much shorter polymers and they are covalently linked to specific proteins
what are other glycosaminoglycans and where are they present
- Chondroitin sulfate- tensile strength in cartilage, tendons, aorta walls
- Dermatan sulfate- pliability of skin, in blood vessels and heart valves
- Keratan sulfates- cornea, cartilage, horny structures and bones
- Heparin- anticoagulant from mast cells
what are glucuronate (GlcA) residues present in chondroitin sulfate replaced by in dermatin
by their epimer, iduronate (IdoA)
Keratan sulfates have no ________ and their sulfate content is variable
uronic acid
variable
what has the highest negative charge density of any known biological macromolecule
Heparin
what is heparin added to for clinical analysis
added to blood samples and to blood donated for transfusion, to prevent clotting
