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Block 3 Week 3 Meg > Schegg: Carb Metabolism III > Flashcards

Schegg: Carb Metabolism III Flashcards

1
Q

What are complex polysaccharides?

A

an oligosaccharide with more than one type of sugar residue

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2
Q

Types of complex polysaccharides

A 
glycoproteins
GPI anchors
glycosylated lipids
GAGs
proteoglycans
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3
Q

Formation of complex polysaccharides dependent on two important classes of enzymes

A
  1. glycosyltransferases

2. glycosidases

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4
Q

These transfer a saccharide from a donor to an acceptor

donor-glycose + acceptor –> glycose-acceptor + donor

A

glycosyltransferases

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5
Q

Glycosyltransferases are very specific for these four things:

A
  1. sugar transferred
  2. acceptor
  3. the site
  4. anomeric linkage formed
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6
Q

These remove specific sugar residues

Also very specific for the bond hydrolyzed

A

glycosidases

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7
Q

Proteins which contain one or more saccharide bound covalently to protein

A

glycoproteins

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8
Q

About what percent of all eukaryotic proteins are glycosylated?

A

50%

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9
Q

Glycoproteins are all synthesized on the rER via the (blank) pathway

A

secretory

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10
Q

How much of a glycoprotein is sugar?

A

Quite variable!

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11
Q

What do the carbohydrate (sugar) portions of glycoproteins look like?

A

Usually less than 12-15 residues
Branched
Heterogeneic

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12
Q

What is the distribution of carbohydrates on glycoproteins?

A

Sometimes evenly distributed across the protein, sometimes in a defined area

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13
Q

Glycoproteins are important for four things

A
  1. cell membranes
  2. mucus constituents
  3. secreted hormones
  4. plasma proteins
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14
Q

T/F: Cell surface glycans are the first molecules encountered by anything that approaches the cell

A

True

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15
Q

Two basic types of glycoproteins

A
  1. N-linked to Asn

2. O linked to Ser or Thr

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16
Q

N-linked glycoproteins have complex structures, but all have (blank) as first sugar residue

A

GlcNAc

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17
Q

The final structure of N-linked glycoproteins can be one of three types

A

high-mannose
hybrid
complex

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18
Q

The common core from N-linked oligosaccharides is assembled on (blank) as a lipid-linked polysaccharide

A

dolichol

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19
Q

N-linked glycoproteins begin on the cytoplasmic side of the ER, accept GlcNAc, get glycosylated, and then are flipped into the (blank), where they are then transferred to a (blank) on a protein being synthesized.

A

ER lumen; Asparagine

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20
Q

After glucoses are removed in the ER, N-linked glycoproteins are moved in vesicles to the (blank) and then one of two things happens. They are either (blank) or sent to (blank).

A

golgi; secreted or in membranes; lysosomes

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21
Q

In (blank) glycoproteins, the protein is synthesized, folded, and moved to the golgi before saccharide units are added.

A

O-linked

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22
Q

Product formed in O-linked glycosylation depends on what?

A

number and type of glycosyltransferases in a cell

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23
Q

In (blank), saccharides are also O-linked to 5-OH Lys

A

collagen

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24
Q

O-linked highly glycosylated glycoproteins that are secreted or membrane-bound
They can form gels that lubricate, provide chemical barriers and hold water

A

Mucins

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25
The oligosaccharide chains of mucin are often sulfated and contain (blank)
sialic acid
26
Disorders of N-linked glycosylation
Type 1: most common, involves early steps in the synthesis of N-linked glycoproteins Type 2: enzymatic defects in N-glycan processing
27
Most common disorder of N-linked glycosylation | -involves early steps in the synthesis of N-linked glycoproteins
Type 1
28
enzymatic defects in N-glycan processing enzymes
Type 2
29
The most common defect in N-linked glycoprotein synthesis is a deficit in (blank)
phosphomannosemutase II
30
- enzymatic defects in O-mannosylation and O-fucosylation example: Walker-Warburg syndrome deficit in O-mannosyltransferase I causes α-dystroglycanopathies (congenital muscular dystrophy)
Disorders of O-linked glycosylation
31
T/F: There are also disorders with combined N- and O-glycosylation defects
True
32
Out of the 40 known CDGs, how many are autosomal recessive? What are the symptoms?
38; psychomotor retardation, malfunction of organ systems
33
There are also disorders of glycoprotein (blank)
degradation
34
If glycoproteins cannot be degraded, what happens?
incompletely degraded compounds accumulate in tissues and urine-->lysosomal storage diseases
35
Deficit in GlcNAc-P glycosyltransferase, the enzyme that marks lysosomal proteins for their destination These proteins are secreted from the cell and are found in plasma and other body fluids
I-cell disease
36
Some glycoproteins are anchored to the extracellular side of plasma membranes via (blank)
GPI (Glycosylphosphatidylinositol)
37
GPI contains a core tetrasaccharide plus additional saccharides. GPI anchors proteins and concentrates them in (blank)
lipid rafts
38
GPI synthesis begins on the (blank) side of the ER. A GlcNAc is added, 3 mannose sugars, an ethanolamine, and a protein. The protein ends up on the exterior of the plasma membrane.
cytoplasmic
39
Glycosyltransferases also synthesize glycolipids. These are mainly (blank)
sphingolipids
40
3 components of a sphingolipid
sphingosine fatty acid X (H, single monosaccharide, or more complex oligosaccharide)
41
4 classes of sphingolipids
cerebrosides sulfatides globosides gangliosides
42
Which class of spingolipids account for 15% of lipids in white matter
sulfatides
43
Globosides and gangliosides are synthesized by a series of specific (blank)
glycosyltransferases
44
What's this? | UDP-Gal + glucocerebroside → lactosyl ceramide (β (1→4))
First step in the synthesis of globosides and gangliosides
45
Disorders of glycolipid degradation mainly affect the (blank). What's the most common one?
nervous system; Tay-Sachs
46
Sphingolipids are degraded by lysosomal enzymes, so a deficiency in lysosomal glycosidases results in (blank)
sphingolipid storage disease
47
If there is a problem in the pathway for the breakdown of GM1, globoside, and sphingomyelin to ceramide, what can occur?
mental retardation, severe mental and motor deterioration
48
Autosomal recessive deficiency in hexosaminidase A A milky halo occurs around the fovea of the eye due build up of ganglioside in ganglion cells. The fovea remains red because there are no ganglion cells in the fovea.
Tay-Sachs disease
49
A, B, and O antigens on the surface of RBCs are (blank). They are erythrocyte surface (blank)
complex polysaccharides; sphingolipids
50
the acceptor for a glycosyltransferase coded for by the ABO gene (on chromosome 9). There are several allelic forms of this gene
H antigen
51
(blank) codes for N-acetylgalactosamine glycosyltransferase. The GalNAc is added to the terminal Gal in an α 1,3 linkage
The A allele
52
(blank) codes for galactosyltransferase. The Gal is added to the terminal Gal in an α 1,3 linkage
The B allele
53
(blank) codes for an inactive protein. Therefore, the O group has neither of these monosaccharides at terminus of the antigen
The O allele
54
The H gene in epithelial and secretory tissues that produces the H antigen is called (blank)
FUT2
55
Antigens are (blank) or (blank), not synthesized by RBCs
glycoproteins; sphingolipids
56
Antigens are produced in epithelial and secretory tissues, but are detected in blood. Why?
the glycosylated sphingolipids circulate in plasma and absorb to the surface of RBCs
57
Long and unbranched heteropolysaccharides Composed of disaccharide repeating units Often have sulfate groups Highly charged
Glycosaminoglycans
58
The charge patterns on (blank) provide for specific recognition by a variety of protein ligands that bind.
GAGs
59
May be attached to extracellular protein to form proteoglycans
GAGs
60
GAGs are found in extracellular spaces in (blank)
ground substance
61
Physical properties of GAGs
``` not easily compressed negatively charged (allows them to absorb water) maintain fluid and electrolyte levels ```
62
A non-sulfated GAG
hyaluronate (hyaluronan)
63
(blank) is a GAG used as an anti-coagulant for patients to reduce clotting post-surgery
heparin
64
What does heparin do reduce clotting?
speeds up the formation of the antithrombin III complex
65
GAGs are assembled using (blank) and sulfation occurs as the chain grows
glycosyltransferases
66
(blank) defect diseases can impair the formation of GAGs, and lead to short stature and bowed limbs
sulfation
67
large molecules with a central protein core and extensions of glycosaminoglycans principle component of the ground substance negatively charged
proteoglycans
68
Example of a proteoglycan with several different GAGs attached to a core protein
aggrecan
69
Proteoglycans are degraded through sequential actions of lysosomal enzymes. Deficiencies in these enzymes cause a variety of (blank).
mucopolysaccharidoses
70
Hurler and Hunter syndrome
defects in degradation of proteoglycans
71
Both proteoglycan and glycoprotein synthesis is controlled at the level of (blank) synthesis
hexosamine
72
Main regulatory step in hexosamine synthesis?
F-6-P-glutamine transaminase
73
Needed for sulfation of GAGs
PAPs
74
Sulfation defect diseases can be caused by defects in (blank) synthetase
PAPs

Block 3 Week 3 Meg (9 decks)

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