Biochem Final Glycoconjugates

Question 1

definition of glyconjugates
main types
functions

Answer 1

carbohydrates covalently linked to other, non carbohydrate biomolecules

proteoglycans (containing glycosaminoglycans), glycoproteins and glycosphingolipids

cell to cell communication/signaling, labeling of proteins (ex. for destruction), recognition sites for extracellular molecules

Question 2

proteoglycans where and what

Answer 2

molecule on the cell surface or ECM (secretory) containing one or move covalently linked glycosaminoglycans

glycosaminoglycans can bind to extracellular proteins through electrostatic interactions (they are negatively charged due to sulfur)

Question 3

glycoproteins where and what

Answer 3

found on outer surface of plasma membrane or in ECM and blood

contain 1 or more oligosaccharides joined covalently to protein

specific for recognition and high-affinity binding by lectins

Question 4

lectins

Answer 4

carb binding proteins

Question 5

glycosphingolipids

Answer 5

components of plasma membrane with oligosaccharide heads (for lectin recognition)

function in nerve conduction and myelin formation, and signal transduction

Question 6

proteoglycan structure

Answer 6

rod shaped with projections of covalently linked glycosaminoglycans

Question 7

GAGs structure

Answer 7

linear polymers of repeating disaccharide units of either: N-acetyl-glucosamine/N-acetyl-galactosamine and uronic acid

Question 8

uronic acid structure

Answer 8

negatively charged due to C6 oxidation forming carboxylate ion

Question 9

GAG function

Answer 9

forms network with fibrous proteins to form ECM in connective tissues and lubrication of joints

Question 10

hyaluronate

Answer 10

GAG with no sulfate group
found in articular cartilage and synovial fluid
~50,000 units, forms large aggregates with aggrecan core protein (bottle brush)

Question 11

glucuronic acid

Answer 11

type of uronic acid

Question 12

chondroitin 4-sulfate

Answer 12

GAG
1 sulfate containing, glucuronic acid containing
found in cartilage around joints

Question 13

keratan sulfate

Answer 13

GAG
no uronic acid/no sugar acid
1 sulfate
found in cornea, cartilage and bone

Question 14

Heparin

Answer 14

GAG
contains iduronic acid, sometimes glucuronic acid
contains 2-3 sulfates
acts as anticoagulant

Question 15

heparane sulfate vs heparin structure

Answer 15

heparane sulfate: found in all cells, contains higher proportion of glucuronic acid, contains less sulfate groups (1)
polysaccharide attached to proteoglycan proteins

heparin: found in specific cells like mast cells, contains higher proportion of iduronic acid
3 sulfate groups
polysaccharide

both are highest negatively charged biomolecules

Question 16

heparane sulfate/heparin function

Answer 16

prevents blood clotting by activating protease inhibitor antithrombin
- antithrombin inhibits coagulation activity of thrombin

binding to cells regulates development and formation of blood vessels

can bind to viruses and bacteria to decrease virulence

Question 17

tetrasaccharide bridge and core protein

Answer 17

4 unit sugar with xylose on the end attached to GAG which links to core protein on proteoglycan protein

core protein is: Ser-Gly-X-Gly
xylose anomeric carbon on bridge links to Ser hydroxyl
ex. aggrecan studied most

Question 18

syndecans vs glypicans

Answer 18

glycosaminoglycans vareties

syndecans: single transmembrane domain (integral membrane protein)

glypicans: protein anchored to lipid membrane with GPI anchor in membrane

Question 19

proteoglycans in ECM structure

Answer 19

proteoglycans interact with receptors from neighboring cells to regulate growth
tissue organizers, influence cellular activity, growth factor activation and adhesion
binds to EC proteins through electrostatic interactions
create structure of cell

Question 20

proteoglycans in articular cartilage

Answer 20

attracts water to reduce friction, provide lubrication and balance load
assemblies of aggrecan core proteins attached to hyaluronan
looks like a bottle brush

Question 21

ECM functions

Answer 21

strength, elasticity and physical barrier
components: proteoglycans, collagen fibers, elastin (fibrous protein)
barrier for cancerous cells trying to invade new tissues - secrete heparinase to degrade ECM

Question 22

integrins vs syndecans
functions

Answer 22

integral receptor protein for extracellular proteoglycans

vs. syndecans which are integral proteoglycans themselves

regulate apoptosis, cell growth, mobility and wound healing

Question 23

glycoproteins definition

Answer 23

protein with one or more small branched or unbranched oligosaccharides attached via anomeric carbon to either Ser, Thr, or Asn
make up 50% mammalian proteins

few bacteria have them, but viral proteins are heavily glycosylated to avoid detection

Question 24

glycoprotein linkages

Answer 24

O-linkages on Ser or Thr hydroxyl, N-linkages to Asn amide

Question 25

glycolipids definition

Answer 25

lipids with covalently bound oligosaccharides, plants and animals
ex. glycosphingolipids - oligosaccharides bound to sphingolipid in membrane
oligosaccharides act as recognition sites for lectins
nerve conduction, myelin formation and signal transduction

Question 26

blood type

Answer 26

oligosaccharide determines blood type, can be attached to protein or lipid
A: N-acetylgalactosamine glycosyltransferase transport of A antigen
B: galactose glycosyltransferase transport of B antigen
O: neither transferase

Question 27

gram negative bacteria

Answer 27

lipopolysaccharides cover peptidoglycan layer
lipid A: region can be endotoxic in some species (toxic effects for host)
core region
O-specific chain region recognized by host immune system

Question 28

mass spectrometry on sugar motifs in gram-negative bacteria

Answer 28

identify types and amounts of sugar motifs to track virulence and how pathogens invade the body

Question 29

in order for informational carb to be bioactive it must

Answer 29

be covalently joined to a protein or lipid