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FTM Exam 1 > DLA Before Lecture 27 > Flashcards

DLA Before Lecture 27 Flashcards

1
Q

N-glycosylation of proteins

A

Protein synthesis begins and the polypeptide chain is extruded into the rER

A mamnose-rich oligosacharide is synthesized on lipid dolichol-PP=pyrophosphate, dolichol has many isoprene units which anchor it in the rER membrane

The oligosacharide is transferred from dolichol to amide N of an asparagine of polypeptide

Trimming of the carbo chain begins as he protein moves thru rER

In Golgi, further trimming and/or addition of monosaccharides, form complex glycoproteins and high-mannose glycoproteins

N-glycosylated glycoproteins are transported into lysosomes, secreted into the blood, or incorporated into the PM

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2
Q

I-cell disease

A

Caused by a deficiency to phosphorylate mannose

Characterized by skeletal abnormalities, restricted joint movement, coarse facial features, and severe phychomotor impairment

Death usually occurs by 8yo

Different molecules are not degraded and accumulate forming inclusion bodies

Diagnosis: detection of inclusions in lymphocytes or cultured skin fibroblasts, released lysosomal enzyme into blood

Mucolipidosis type II

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3
Q

Lysosomal enzymes

A

N-linked glycoroteins the receive in the cid-Golgi a mannose 6-P marker > formed by a specific phosphotransferase which recognizes all potential lysosomal enzymes

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4
Q

Mannose 6-P receptors

A

In the trans-Golgi bind the marked enzymes and package them into vesicles for transport into lysosomes

Recycled and enzyme is active inside lysosomes after cleavage of the phosphate of the M6P marker

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5
Q

Proteoglycan

A

Contain mainly GAGs (up to 95%) and a small amount of protein

O-glycosylation of the core protein

Part of ECM

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6
Q

Glycoprotein

A

Mainly protein and a small amount of sugar which are often branched

O- and N-glycosylation

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7
Q

Residues for O-linked glycosylation

A

Serine of threonine

Hydroxy-lysine in collagen

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8
Q

Steps for O-glycosylation of proteins

A

Protein is synthesized on the rER and extrudes into its lumen

The first sugar is enzymatically transferred and linked directly to OH or ser and thr or hydroxylysine

Sugars in O-linkage are added individually directly to the protein mainly in the Golgi by glycosyl transferase bound to the Golgi membrane

Enzyme recognize actual structure and add individually the appropriate sugar

used in synthesis of proteoglycans, glycocalyx, blood group, and mucins

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9
Q

Blood types

A

O-linked glycoproteins

H substance = Fuc-Gal-GlcNAc-R (R is protein or ceramide = lipid)

Type O: no sugar linked to Gal of H substance

Type A: GalNAc linked to Gal

Type B: galactose linked to Gal

Type AB: mixture of type A and B

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10
Q

Mucins

A

Special glycoproteins that contain 50% carbohydrates

Protein is rich in ser and thr for O-linkage

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11
Q

Salivary mucins

A

1 N-acetylglucosamine linked to ser or thr

This sugar binds to sialic acid (NANA) > mucins with many negative charges

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12
Q

Mucus

A

Mucins and water, protect and lubricates many internal body surfaces

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13
Q

Glycocalyx of endothelial cells components and functions

A

Glycoproteins and glycolipids

Cell-cell recognition
Sieving barrier
Inhibition of platelet adherence
Prevention of leukocyte adhesion

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14
Q

Unwanted binding and adherence by viruses and bac

A

Viruses that infect animal cells (influnza virus) bind to glycoproteins on the cell surface as the first step of infection

Bac adhere and colonize or infect
Bac toxin bind to a surface glycolipid before entering cell

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15
Q

E. coli attaches to

A

Mannose residue on PM of human cheek cells

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16
Q

Helicobacter pyloci attaches to

A

The gastric surface

This bac leads to ulcers by interact with a specific blood gp antigen of the gastric epothelium

17
Q

Structure of glycosaminoglycans = GAGs

A

Long, branched chains of negatively charged sugars, often sulfated

Repeating disaccharide units:
Position 1: acidic sugar > glucouronic acid or iduronic acid
Position 2: amino sugar > glucosamine of galactosamine, can be acetylated

18
Q

Resilience of GAGs

A

Strong negative charges from the carboxyl and sulfate gps

Bind large amounts of water producing a gel-link matrix, part of ECM

React to compression with squeezing water out and to relaxation with absorbing water

19
Q

Functions of GAGs

A

Flexible support of ECM

Molecular sieve

Lubricants

Shock-absorber

20
Q

Chondroitin sulfates

A

Most abundant GAGs in the body

Sulfated in position 4 or 6

Found in:
Cartilage
Bone
Ligaments
Aorta

Glucuronic acid > beta 1-3 > N-acetyl galactosamine

21
Q

Keratan sulfates = KS

A

Contain sulfated galactose in position 1

Most heterogenous regarding their sugar

Found in:
Cartilage
Cornea, where need transparence

Gla > beta 1-4 > GlcNAC

22
Q

Dermatan sulfates

A

Found in:
Skin
Blood vessel
Heart valve

IdUA > beta 1-3 > GalNAC

23
Q

Heparan sulfate

A

Found in:
BM
Cell surface for recognition

Sulfated glucuronic acid or iduronic acid
GlcUA > alpha 1-4 > GlcN

24
Q

Heparin

A

Anticoagulant: facilitate inhibition of thrombin

Contain many iduronyl sulfates
GAG with the largest amount of sulfates and negative charges

Not in ECM, in mast cells that line arteries of lung, liver, and spleen

Released from intracellular granules

25
Q

Hyaluronic acid is a special GAG that is

A

Not sulfated

Not colavently attached to a protein

Synthesized step by step directly into the extracellular space

Provides extracellularly the central strand in proteoglycan aggregates

Connected to core protein via link proteins

26
Q

Locations and functions of hyaluronic acid

A 
Found in:
Vitreous humor of the eye
Synovial fluid of the joints
Cartilage
Loose connective tissues

Facilitates cell migration in:
Embryogenesis (neural tube closure)
Morphogenesis
Wound repair

27
Q

Proteoglycan aggregates

A

Assembled in ECM using hyaluronic acid and proteoglycans

Proteoglycans are formed intracellularly by O-glycosylation of the core protein and are then released into the ECM

Shock absorber and lubricant

28
Q

GAG linkage region

A

Core protein-serine side chain-trihexoside linker region-GAGs

FTM Exam 1 (23 decks)

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