Ch. 9: Glyconjugates/proteins/lipids

Question 1

What is a glycoprotein?

Answer 1

Proteins w/covalently attached polysaccharide chain

Question 2

Glycoprotein fxn: structure

Example?

Answer 2

Collagen

Question 3

Glycoprotein fxn: lubrication and protection

Examples?

Answer 3

Epithelial mucins

Synovial fluid

Question 4

Glycoprotein fxn: transport

Answer 4

Ceruloplasmin (copper carrier)

Transferrin (iron carrier)

Question 5

Glycoprotein fxn: Endocrine regulation

Answer 5

Thyrotropin
Chorionic gonadotropin
Erythropoietin

Question 6

Glycoprotein fxn: catalysis

Examples?

Answer 6

Proteases
Nucleases
Glycosidases
Hydrolases

Question 7

Glycoprotein fxn: Membrane receptors

Examples?

Answer 7

hormones (insulin)
Ach
Cholera toxin
Electromagnetic radiation (rhodopsin)

Question 8

Glycoprotein fxn: antigens

Examples?

Answer 8

Blood group substances

Question 9

Glycoprotein fxn: defense against infection

Examples?

Answer 9

Ig's 
Complement proteins
Interferon
Selectins
Integrins

Question 10

Glycoprotein fxn: cell-cell recognition and adhesion

Examples?

Answer 10

Fibronectin
Laminin
Chondronectin

Question 11

Glycoprotein fxn: miscellaneous

Examples?

Answer 11

Glycophorin (intrinsic red blood cell membrane constituent)

Intrinsic factor (absorb dietary vit B12)

Clotting factors (fibrinogen)

Question 12

a.a. in O-linked glycosidic linkages?

Type of attachment?

Answer 12

Serine
Threonine
Hydroxylated lysine
Hydroxylated proline

Simple attachment

Question 13

a.a. in N-linked glycosidic linkages?

Type of attachment?

Answer 13

Asparagine

Complicated attachment

Question 14

Beta-N-glycosidic link: N-acetylglucosamine and Asn

Found where?

Answer 14

Wide occurrence

Question 15

Alpha-O-glycosidic link: N-acetylgalactosamine and ser/thr

Found where?

Answer 15

Mucus secretions

Blood group substances

Question 16

Beta-O-glycosidic linkage: galactose & OH-lys

Found where?

Answer 16

Collagen

Question 17

Beta-O-glycosidic link: xylopyranose & Ser

Found where?

Answer 17

Thyroglobulin

Proteoglycans

Question 18

Where are glycoproteins synthesized? (Glycosylation)

Answer 18

ER and Golgi

Question 19

How are glycoproteins made via glycosylation?

Answer 19

Sequential addition of monosaccharide units to non-reducing end ➡️ CHO chain

Question 20

Which activated sugars act as precursors for glycosylation?

Answer 20

UDP-sugars
GDP-mannose
GDP-L-fructose
CMP-NANA

Question 21

Membrane phospholipid involved in N-glycosylation?

Answer 21

Dolichol phosphate

sugars added to dolichol (ER membrane) ➡️ CHO chain transferred to Asn

Question 22

What is non-enzymatic glycation?

Answer 22

Addition of CHO residues w/out complex enzymatic pathways

Question 23

Hemoglobin A1c: linkage?

Short or long term glucose control indicator?

Answer 23

N-glycosidic link to N-terminal amino group of valine (each beta chain)

Long term (2-3 month lifespan)

Question 24

Human serum albumin (HSA): produces what condensation product?

Short or long term glucose control indicator?

Answer 24

Fructosamine

Short term (1-3 week lifespan)

Question 25

Human lens proteins (alpha, beta, gamma-crystallins): age-dependent, non-enzymatic glycation at?

Answer 25

Epsilon-amino groups of lys

Question 26

Fxn of fibronectin?

Answer 26

Promotes attachment & subsequent spreading of many cell types

Question 27

3 types of fibronectin?

Answer 27

Cell-surface: adhesion of cell w/ECM Plasma: wound repair Fetal: marker for risk for preterm delivery

Question 28

Binding sites of fibronectin? (NH2 ➡️ S-S)

Answer 28

Fibrin, collagen, (3X), cells, heparin, fibrin

Question 29

What are blood group antigens?

Answer 29

Oligosaccharides on surface of human RBCs

Question 30

What determines antigenic variation of blood groups?

Answer 30

Specific glycotransferases which synthesize the specific oligosaccharides (enzymes inherited)

Question 31

A antigen: what sugar is added?

Answer 31

N-acetylgalactosamine

Question 32

B antigen: what sugar is added?

Answer 32

Galactose

Question 33

O (H antigen): what sugar added?

Answer 33

None (no enzyme)

Question 34

Blood type O: antigens present? Antibodies in serum? Serum type causing agglutination when mixed with RBCs?

Answer 34

H Anti-A, Anti-B None

Question 35

Blood type A: antigens present? Antibodies in serum? Serum type causing agglutination when mixed with RBCs?

Answer 35

A Anti-B O, B

Question 36

Blood type B: antigens present? Antibodies in serum? Serum type causing agglutination when mixed with RBCs?

Answer 36

B Anti-A O, A

Question 37

Blood type AB: antigens present? Antibodies in serum? Serum type causing agglutination when mixed with RBCs?

Answer 37

A, B None O, A, B

Question 38

All serum proteins are glycoproteins EXCEPT: ?

Answer 38

serum albumin (but can be glycated)

Question 39

How does liver recycle glycoproteins? (steps)

Answer 39

Neuraminidase (sialidase) removes terminal sialic acid ➡️ exposes galactose (asialoglycoprotein) ➡️ binding to hepatocyte receptors ➡️ taken up ➡️ receptor-mediated endocytosis ➡️ lysosomal degradation

Question 40

What is elevated in liver disease?

Answer 40

Plasma asialoglycoproteins

Question 41

What is Guillain-Barré syndrome (GBS)?

Answer 41

Autoimmune disease (acute neuropathy) Caused by antecedent, acute bacterial or viral infection Also seen in children after vaccination

Question 42

Describe molecular mimicry of C. jejuni

Answer 42

Lipopolysaccharides have terminal tetrasaccharides similar to human gangliosides GM1 ➡️ immune system confused ➡️ immune-mediated destruction of nerve fibers