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Med 105 > Polysaccharides > Flashcards

Polysaccharides Flashcards

1
Q

what are polysaccharides also called

A

glycans

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2
Q

Some Homopolysaccharides Are Stored Forms of ____

A

Fuel

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3
Q

why are starch and glycogen heavily hydrated

A

because they have many exposed hydroxyl groups available to hydrogen-bond with water

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4
Q

what does amylose and amylopectin contain

A

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

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5
Q

describe the structure of glycogen

A

is a polymer of (α1→4) -linked subunits of glucose, with (α1→6) -linked branches

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6
Q

what is more branched and compact, starch or glycgen

A

glycogen

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7
Q

where is glycogen in the body

A

abundant in the liver, it is also present in skeletal muscle

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8
Q

glycogen molecule has as many__________ ends as it has branches, but only one ________ end

A

nonreducing

reducing

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9
Q

how is glycogen broken down as an energy source

A

glucose units are removed one at a time from the nonreducing ends

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10
Q

how are starch and glycogen ingested in the diet

A

hydrolyzed by α-amylases, enzymes in saliva and intestinal secretions that break (α1→4) glycosidic bonds between glucose units

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11
Q

what is the structure of cellulose

A

linear, unbranched homopolysaccharide, consisting of 10,000 to 15,000 D-glucose units

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12
Q

how are the glucose residues in cellulose linked

A

by (β1→4) glycosidic bonds

This difference gives cellulose and amylose very different structures and physical properties

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13
Q

what is the structure of chitin

A

linear homopolysaccharide composed of N-acetylglucosamine residues in β linkage

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14
Q

what is the chemical difference between cellulose and chitin

A

replacement of the hydroxyl group at C-2 with an acetylated amino group in chitin

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15
Q

what is the rigid component of bacterial cell walls

A

heteropolymer of alternating (β1→4)-linked N-acetylglucosamine and N-acetylmuramic acid residues

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16
Q

how does lysozyme kill bacteria

A

by hydrolyzing the (β1→4) glycosidic bond between N-acetylglucosamine and N-acetylmuramic acid

17
Q

Lysozyme is notably present in ______, presumably as a defense against bacterial infections of the_____

A

tears

eye

18
Q

how do penicillin and other antibiotics kill bacteria

A

by preventing synthesis of the cross-links, leaving the cell wall too weak to resist osmotic lysis

19
Q

what are glycosaminoglycans

A

heteropolysaccharides of linear polymers composed of repeating disaccharide units

20
Q

what are the are the two monosaccharides contained in glycosaminoglycans

A
  • either N-acetylglucosamine or N-acetylgalactosamine

* other is in most cases a uronic acid, usually D-glucuronic or L-iduronic acid

21
Q

In some glycosaminoglycans what are the hydroxyls of the amino sugar esterified with

A

sulfate

22
Q

what forms proteoglycans

A

Glycosaminoglycans attached to extracellular proteins

23
Q

what is hyaluronic acid

A

a glycosaminoglycan containing alternating residues of D-glucuronic acid and N-acetylglucosamine

24
Q

what is the functions of hyaluronic acid

A

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

25
Q

what secretes Hyaluronidase and what does it do

A

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

26
Q

a similar enzyme to Hyaluronidase in sperm hydrolyzes ____________

A

an outer glycosaminoglycan coat around the ovum, allowing sperm penetration

27
Q

how do other glycosaminoglycans differ from hyaluronate

A

they are generally much shorter polymers and they are covalently linked to specific proteins

28
Q

what are other glycosaminoglycans and where are they present

A
  1. Chondroitin sulfate- tensile strength in cartilage, tendons, aorta walls
  2. Dermatan sulfate- pliability of skin, in blood vessels and heart valves
  3. Keratan sulfates- cornea, cartilage, horny structures and bones
  4. Heparin- anticoagulant from mast cells
29
Q

what are glucuronate (GlcA) residues present in chondroitin sulfate replaced by in dermatin

A

by their epimer, iduronate (IdoA)

30
Q

Keratan sulfates have no ________ and their sulfate content is variable

A

uronic acid

variable

31
Q

what has the highest negative charge density of any known biological macromolecule

A

Heparin

32
Q

what is heparin added to for clinical analysis

A

added to blood samples and to blood donated for transfusion, to prevent clotting

Med 105 (16 decks)

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