Ch. 9: Glyconjugates/proteins/lipids Flashcards Preview

Medical Biochemistry > Ch. 9: Glyconjugates/proteins/lipids > Flashcards

Flashcards in Ch. 9: Glyconjugates/proteins/lipids Deck (42):
1

What is a glycoprotein?

Proteins w/covalently attached polysaccharide chain

2

Glycoprotein fxn: structure

Example?

Collagen

3

Glycoprotein fxn: lubrication and protection

Examples?

Epithelial mucins
Synovial fluid

4

Glycoprotein fxn: transport

Ceruloplasmin (copper carrier)
Transferrin (iron carrier)

5

Glycoprotein fxn: Endocrine regulation

Thyrotropin
Chorionic gonadotropin
Erythropoietin

6

Glycoprotein fxn: catalysis

Examples?

Proteases
Nucleases
Glycosidases
Hydrolases

7

Glycoprotein fxn: Membrane receptors

Examples?

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

8

Glycoprotein fxn: antigens

Examples?

Blood group substances

9

Glycoprotein fxn: defense against infection

Examples?

Ig's
Complement proteins
Interferon
Selectins
Integrins

10

Glycoprotein fxn: cell-cell recognition and adhesion

Examples?

Fibronectin
Laminin
Chondronectin

11

Glycoprotein fxn: miscellaneous

Examples?

Glycophorin (intrinsic red blood cell membrane constituent)

Intrinsic factor (absorb dietary vit B12)

Clotting factors (fibrinogen)

12

a.a. in O-linked glycosidic linkages?

Type of attachment?

Serine
Threonine
Hydroxylated lysine
Hydroxylated proline

Simple attachment

13

a.a. in N-linked glycosidic linkages?

Type of attachment?

Asparagine

Complicated attachment

14

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

Found where?

Wide occurrence

15

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

Found where?

Mucus secretions
Blood group substances

16

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

Found where?

Collagen

17

Beta-O-glycosidic link: xylopyranose & Ser

Found where?

Thyroglobulin
Proteoglycans

18

Where are glycoproteins synthesized? (Glycosylation)

ER and Golgi

19

How are glycoproteins made via glycosylation?

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

20

Which activated sugars act as precursors for glycosylation?

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

21

Membrane phospholipid involved in N-glycosylation?

Dolichol phosphate

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

22

What is non-enzymatic glycation?

Addition of CHO residues w/out complex enzymatic pathways

23

Hemoglobin A1c: linkage?

Short or long term glucose control indicator?

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

Long term (2-3 month lifespan)

24

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

Short or long term glucose control indicator?

Fructosamine

Short term (1-3 week lifespan)

25

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

Epsilon-amino groups of lys

26

Fxn of fibronectin?

Promotes attachment & subsequent spreading of many cell types

27

3 types of fibronectin?

Cell-surface: adhesion of cell w/ECM

Plasma: wound repair

Fetal: marker for risk for preterm delivery

28

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

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

29

What are blood group antigens?

Oligosaccharides on surface of human RBCs

30

What determines antigenic variation of blood groups?

Specific glycotransferases which synthesize the specific oligosaccharides (enzymes inherited)

31

A antigen: what sugar is added?

N-acetylgalactosamine

32

B antigen: what sugar is added?

Galactose

33

O (H antigen): what sugar added?

None (no enzyme)

34

Blood type O: antigens present?

Antibodies in serum?

Serum type causing agglutination when mixed with RBCs?

H
Anti-A, Anti-B
None

35

Blood type A: antigens present?

Antibodies in serum?

Serum type causing agglutination when mixed with RBCs?

A

Anti-B

O, B

36

Blood type B: antigens present?

Antibodies in serum?

Serum type causing agglutination when mixed with RBCs?

B

Anti-A

O, A

37

Blood type AB: antigens present?

Antibodies in serum?

Serum type causing agglutination when mixed with RBCs?

A, B

None

O, A, B

38

All serum proteins are glycoproteins EXCEPT: ?

serum albumin (but can be glycated)

39

How does liver recycle glycoproteins? (steps)

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

40

What is elevated in liver disease?

Plasma asialoglycoproteins

41

What is Guillain-Barré syndrome (GBS)?

Autoimmune disease (acute neuropathy)

Caused by antecedent, acute bacterial or viral infection
Also seen in children after vaccination

42

Describe molecular mimicry of C. jejuni

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