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

Ch. 9: Glyconjugates/proteins/lipids Flashcards

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USMLE® Step 1 flashcards
1
Q

What is a glycoprotein?

A

Proteins w/covalently attached polysaccharide chain

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2
Q

Glycoprotein fxn: structure

Example?

A

Collagen

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3
Q

Glycoprotein fxn: lubrication and protection

Examples?

A

Epithelial mucins

Synovial fluid

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4
Q

Glycoprotein fxn: transport

A

Ceruloplasmin (copper carrier)

Transferrin (iron carrier)

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5
Q

Glycoprotein fxn: Endocrine regulation

A

Thyrotropin
Chorionic gonadotropin
Erythropoietin

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6
Q

Glycoprotein fxn: catalysis

Examples?

A

Proteases
Nucleases
Glycosidases
Hydrolases

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7
Q

Glycoprotein fxn: Membrane receptors

Examples?

A

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

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8
Q

Glycoprotein fxn: antigens

Examples?

A

Blood group substances

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9
Q

Glycoprotein fxn: defense against infection

Examples?

A 
Ig's 
Complement proteins
Interferon
Selectins
Integrins
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10
Q

Glycoprotein fxn: cell-cell recognition and adhesion

Examples?

A

Fibronectin
Laminin
Chondronectin

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11
Q

Glycoprotein fxn: miscellaneous

Examples?

A

Glycophorin (intrinsic red blood cell membrane constituent)

Intrinsic factor (absorb dietary vit B12)

Clotting factors (fibrinogen)

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12
Q

a.a. in O-linked glycosidic linkages?

Type of attachment?

A

Serine
Threonine
Hydroxylated lysine
Hydroxylated proline

Simple attachment

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13
Q

a.a. in N-linked glycosidic linkages?

Type of attachment?

A

Asparagine

Complicated attachment

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14
Q

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

Found where?

A

Wide occurrence

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15
Q

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

Found where?

A

Mucus secretions

Blood group substances

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16
Q

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

Found where?

A

Collagen

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17
Q

Beta-O-glycosidic link: xylopyranose & Ser

Found where?

A

Thyroglobulin

Proteoglycans

18
Q

Where are glycoproteins synthesized? (Glycosylation)

A

ER and Golgi

19
Q

How are glycoproteins made via glycosylation?

A

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

20
Q

Which activated sugars act as precursors for glycosylation?

A

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

21
Q

Membrane phospholipid involved in N-glycosylation?

A

Dolichol phosphate

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

22
Q

What is non-enzymatic glycation?

A

Addition of CHO residues w/out complex enzymatic pathways

23
Q

Hemoglobin A1c: linkage?

Short or long term glucose control indicator?

A

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

Long term (2-3 month lifespan)

24
Q

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

Short or long term glucose control indicator?

A

Fructosamine

Short term (1-3 week lifespan)

25
Q

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

A

Epsilon-amino groups of lys

26
Q

Fxn of fibronectin?

A

Promotes attachment & subsequent spreading of many cell types

27
Q

3 types of fibronectin?

A

Cell-surface: adhesion of cell w/ECM

Plasma: wound repair

Fetal: marker for risk for preterm delivery

28
Q

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

A

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

29
Q

What are blood group antigens?

A

Oligosaccharides on surface of human RBCs

30
Q

What determines antigenic variation of blood groups?

A

Specific glycotransferases which synthesize the specific oligosaccharides (enzymes inherited)

31
Q

A antigen: what sugar is added?

A

N-acetylgalactosamine

32
Q

B antigen: what sugar is added?

A

Galactose

33
Q

O (H antigen): what sugar added?

A

None (no enzyme)

34
Q

Blood type O: antigens present?

Antibodies in serum?

Serum type causing agglutination when mixed with RBCs?

A

H
Anti-A, Anti-B
None

35
Q

Blood type A: antigens present?

Antibodies in serum?

Serum type causing agglutination when mixed with RBCs?

A

A

Anti-B

O, B

36
Q

Blood type B: antigens present?

Antibodies in serum?

Serum type causing agglutination when mixed with RBCs?

A

B

Anti-A

O, A

37
Q

Blood type AB: antigens present?

Antibodies in serum?

Serum type causing agglutination when mixed with RBCs?

A

A, B

None

O, A, B

38
Q

All serum proteins are glycoproteins EXCEPT: ?

A

serum albumin (but can be glycated)

39
Q

How does liver recycle glycoproteins? (steps)

A

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

40
Q

What is elevated in liver disease?

A

Plasma asialoglycoproteins

41
Q

What is Guillain-Barré syndrome (GBS)?

A

Autoimmune disease (acute neuropathy)

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

42
Q

Describe molecular mimicry of C. jejuni

A

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

Medical Biochemistry (23 decks)

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