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Bchem 393 > Glycoprotiens > Flashcards

Glycoprotiens Flashcards

1
Q

What are the two ways that carbs are attached to protiens

A

O linked and N linked glycosylation

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2
Q

What is o linked glycosylation

A

The carbs are attached to the oh on the side chains of serine or threonine residues

The glycosidic bond forms between the anomeric carbon of the carb and the O of the oh in the side chain

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3
Q

What is N linked glycosylation

A

The carbs attache to the side chain amine nitrogen (NH2) of Asparagine (N) residues

The glycosidic bond forms between the anomeric carbon of the carb and the Nitrogen of the side chain

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4
Q

How are the bonds between carbs and protiens formed

A

The reaction is catalyzed by enzymes called glycosyltransferases

Originally the carb is attached to a activated sugar nucleotide (UDP)

The bond it broken and the new bond between the protiens nucleotide and the carb is formed

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5
Q

What are N linked olgigoraccharides

A

The oligosaccharides acts as a chemical tag on the protiens

There’s high mannose type and complex type

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6
Q

What feature of carb make them good information rich molecules

A

They vary in the identity and number of monosaccharides joined together

The have different types of linkages (alpha 1 6, beta 1,4)

The have either beta or alpha anomers

They have either o or n linked glycosidic bonds to protiens

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7
Q

How does being glycosylation (adding a carb) change the properties of a protien

A

It increases the amount of chemical info and functionally of the protiens

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8
Q

50 % of protiens are

A

Glycosylated

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9
Q

What are the three classes of glycoproteins

A

Glycoprotien

Proteoglycan

Mucin

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10
Q

What is the class glycoprotien

A

There more protien than carbs by weight

They have diverse roles in function

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11
Q

What is the class proteoglycan

A

More carb than protien

Has structural and lubricant roles

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12
Q

What is the class mucin

A

More carb than protien

Role as lubricants and barriers

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13
Q

What is erythropoietin (EPO)

A

A glycoprotien

A hormone that stimulate the produciton of red blood cells and is 40% carb

It’s made of 3 N linked (to asn) and 1 o linked (to serine)

Being glycosylated enhances stability and function of the protien

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14
Q

What is special about recombinants EPO

A

They have diff glycosylation than the ones in naturally in the body

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15
Q

What are proteoglycans function

A

They are lubricants and have roles as structural components in connective tissues

The adhere cells to the extracellular matrix

The protiens are attached to glycosaminoglycans (which make up 95% by weight)

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16
Q

What is cartilage made of

A

The Proteoglycan aggrecan and collagen

17
Q

What are glycosaminoglycans structure and function

A

They are repeating disaccharide with negatively charged coo- and sulphate (SO3-)

They bind water very well because of the - charge

In proteoglycans

18
Q

What is aggrecan

A

A Proteoglycan

Repeating disaccharides of chondrotin and keratin sulphate (which are glycosaminoglycans) that are extending from the protiens polypeptide chain

Each of these protein carb complexes are attached to a strand called hyaluronate

The aggrecan acts as a sponge, when there is pressure it releases water and if less pressure it absorbs water due to the negative charges

19
Q

What are mucins structure and function

A

They are components in mucus , ex MUC2

Are made up of VNTRs (variable number of tandem repeats)

They’re 80% of carbs by weight, o linked glycosylation

Act as a lubricant in saliva and as a protective barrier when attached to epithelial cells in the intestine (covered by mucus to protect the cells)

20
Q

What are lectins

A

Protiens that recognize and bind to specific carbs by noncovalent interactions

Ex. Selectin

21
Q

What are selectins

A

A class of lectin

Recruits immune system cells to bind to the site of an injury

22
Q

What is hemagglutinin

A

A type of lectin that promotes interactions between cells

Ex. hemagglutinin is on influenza and help it bind to the surface or tester cell and the virus do endocytosis

The virus then need to leave the cell and when it’s released it’s stil bound to the host cell because of hemagglutinin so the enzyme neuraminadase cleaves the carbs and lets the virus leave

Bchem 393 (31 decks)

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