L13- Carbohydrate Conjugation

Question 1

Which carbon of monosaccharides is chemically reactive?

Answer 1

The anomeric carbon.

Question 2

What is a glycoside?

Answer 2

The product of the condensation of a sugar with a hydroxyl-containing molecule.

Question 3

What is the difference between a glucoside and a galactoside?

Answer 3

Glucosides are glycosides that have a glucose, whereas galactosides have a galactose.

Question 4

What is a glycosidic bond?

Answer 4

A covalent bond that joins a sugar to the hydroxyl group of another molecule.

Question 5

Maltose is composed of which sugars bound in what linkage?

Answer 5

Two molecules of glucose in an alpha(1->4)-linkage.

Question 6

Lactose is composed of which sugars bound in what linkage?

Answer 6

Galactose and glucose in a beta(1->4)-linkage.

Question 7

Sucrose is composed of which sugars bound in what linkage?

Answer 7

Glucose and fructose in an alpha(1->2)-linkage.

Question 8

What is the composition and structure of amylose?

Answer 8

Amylose is a starch composed of glucose molecules in alpha(1->4)-linkages. Its structure is that of an unbranched polymer that typically forms a helical coil within cells.

Question 9

What is the composition and structure of amylopectin?

Answer 9

Amylopectin is a starch composed of glucose polymers arranged in alpha(1->4)-linkages. It has branches in alpha(1->6)-linkages every 10-12 residues.

Question 10

What is the composition and structure of glycogen?

Answer 10

Glycogen is a carbohydrate composed of glucose polymers arranged in alpha(1->4)-linkages. It has branches in alpha(1->6)-linkages every 8-10 residues and it exists as spherical particles in cells.

Question 11

What is the composition and structure of cellulose?

Answer 11

Cellulose is composed of glucose polymers arranged in beta(1->4)-linkages. It is typically unbranched.

Question 12

What is the composition and structure of dextrans?

Answer 12

Dextrans are composed of glucose polymers arranged in alpha(1->6)-linkages. They have some branches in alpha(1->3)-linkages.

Question 13

What are glycosaminoglycans (GAGs)?

Answer 13

They are long unbranched polysaccharides of repeating anionic disaccharides. They may be sulfated and are an important component of connective tissues.

Question 14

What is a proteoglycan?

Answer 14

Glycosaminoglycans that are covalently linked to a protein.

Question 15

Which glycosaminoglycan (GAG) is not linked to a core protein?

Answer 15

Hyaluronic acid.

Question 16

Alpha(1->4)- vs. beta(1->4)-linkages. Which can we NOT digest?

Answer 16

Beta(1->4)-linkages.

Question 17

What is the composition and location of hyaluronic acid?

Answer 17

Hyaluronic acid is composed of repeating disaccharides of D-glucuronic acid and N-acetylglucosamine. It is typically found in connective tissue like synovial fluid in joint spaces and in the vitreous fluid of the eye.

Question 18

Which chemical reaction involves the formation of a Schiff base between the aldehyde of a sugar and the amino group of a protein to generate a ketoamine?

Answer 18

Glycation.

Question 19

True or False. Glycation is a form of tissue damage.

Answer 19

True.

Question 20

What is the clinical significance of hemoglobin A1c (HbA1c)?

Answer 20

HbA1c provides a 3-month ‘history’ of blood glucose levels.

Question 21

What is aggrecan?

Answer 21

It is a proteoglycan (composed of chondrotoin sulfate attached to collagen type II) that acts as a shock absorber by cycling water in and out of cartilage.

Question 22

Which nucleotide is NOT involved in the activation of sugars?

Answer 22

Adenine.

Question 23

Which amino acids are involved in N-linked glycosylation?

Answer 23

Asparagine (almost always).

Question 24

Which amino acids are involved in O-linked glycosylation?

Answer 24

Serine and threonine.

Question 25

What is glycosylation?

Answer 25

An enzymatic reaction for secreted or extracellular protein (including proteins that are meant to be stored in the ER lumen).

Question 26

Which glycoprotein is typically NOT secreted from cells?

Answer 26

O-linked N-acetylglucosamine (O-GlcNac).

Question 27

In which cellular compartment are O-linked glycoproteins usually glycosylated?

Answer 27

The Golgi apparatus.

Question 28

Which class of enzymes adds sugars to a growing O-linked glycoprotein?

Answer 28

Glycosyltransferases.

Question 29

True or False. O-links of glycoproteins have carbohydrate molecules first added as a pre-assembled 14 sugar block.

Answer 29

False. The statement is true for N-linked glycoproteins.

Question 30

What lipid carrier molecule is used for the synthesis of the branched oligosaccharide of N-linked glycoproteins?

Answer 30

Dolichol phosphate.

Question 31

Which sugars are used for the synthesis of the initial branched chain oligosaccharide of N-linked glycoproteins?

Answer 31

N-acetylglucosamine, mannose and glucose.

Question 32

Where in the cell are sugars added to proteins to form N-linked glycoproteins?

Answer 32

The ER membrane.

Question 33

Which antibiotic inhibits the addition of N-acetylglucosamine-phosphate to dolichol phosphate?

Answer 33

Tunicamycin.

Question 34

What class of enzymes is responsible for degradation of glycoproteins?

Answer 34

Glycosidases.

Question 35

Deficiency of acid glucosidase results in what storage disease?

Answer 35

Pompe's syndrome.

Question 36

What is the enzymatic defect in Hunter syndrome?

Answer 36

Iduronate sulfatase.

Question 37

What are proteoglycans?

Answer 37

Macromolecules consisting of polysaccharide glycosaminoglycan chains that are attached to core proteins.

Question 38

What is the most abundant glycosaminoglycan in the human body?

Answer 38

Condrotoin sulfate.

Question 39

Where is keratan sulfate type I typically found in the human body?

Answer 39

The cornea.

Question 40

Where is keratan sulfate type II typically found in the human body?

Answer 40

Cartilage.

Question 41

Which class of proteins bind carbohydrates?

Answer 41

Lectins.

Question 42

What is the difference between the terminal sites of Type A, B and O blood groups?

Answer 42

Type A blood has UDP-N-acetylgalactosamine as a terminal residue, Type B has UDP-galactose and Type O has neither.

Question 43

H-pylori preferentially binds to gastric epithelial cells of individuals with which blood type?

Answer 43

O-type.