Deck 7: Carbohydrates and Glycobiology

Question 1

From the abbreviated name of the compound Gal( $\beta$ 1 $\rightarrow$ 4)Glc,we know that:

A)C-4 of glucose is joined to C-1 of galactose by a glycosidic bond.
B)the compound is a d-enantiomer.
C)the galactose residue is at the reducing end.
D)the glucose is in its pyranose form.
E)the glucose residue is the $\beta$ anomer.

Answer 1

C-4 of glucose is joined to C-1 of galactose by a glycosidic bond.

Question 2

Hemoglobin glycation is a process where is attached to hemoglobin.

A)glycerol;covalently
B)glucose;enzymatically
C)glucose;non-enzymatically
D)N-acetyl-galactosamine;enzymatically
E)galactose;non-enzymatically

Answer 2

glucose;non-enzymatically

Question 3

When forming the disaccharide maltose from two glucose monosaccharides:

A)water is eliminated.
B)a hemiacetal is converted to an acetal.
C)the resulting dissacharide is no longer a reducing sugar.
D)Both A and B
E)A,B,and C above

Answer 3

Both A and B

Question 4

Following complete hydrolysis of a sample of glycogen and a sample of cellulose,which of the following must be true?

A)The glycogen sample is more soluble than the cellulose sample.
B)The cellulose sample is more soluble than the glycogen sample.
C)Both samples consist of a mixture of $\alpha$ -d-glucose and $\beta$ -d-glucose.
D)The glycogen sample has a higher ratio of $\alpha$ -d-glucose than the cellulose sample.
E)The cellulose sample contains only $\beta$ -d-glucose.

Question 5

Which of the following is an epimeric pair?

A)d-glucose and d-glucosamine
B)d-glucose and d-mannose
C)d-glucose and l-glucose
D)d-lactose and d-sucrose
E)l-mannose and l-fructose

Question 6

When the linear form of glucose cyclizes,the product is a(n):

A)anhydride.
B)glycoside.
C)hemiacetal.
D)lactone.
E)oligosaccharide.

Question 7

To possess optical activity,a compound must be:

A)a carbohydrate.
B)a hexose.
C)asymmetric.
D)colored.
E)D-glucose.

Question 8

The reference compound for naming D and L isomers of sugars is:

A)fructose.
B)glucose.
C)glyceraldehyde.
D)ribose.
E)sucrose.

Question 9

Which of the following monosaccharides is not an aldose?

A)Erythrose
B)Fructose
C)Glucose
D)Glyceraldehyde
E)Ribose

Question 10

When two carbohydrates are epimers:

A)one is a pyranose,the other a furanose.
B)one is an aldose,the other a ketose.
C)they differ in length by one carbon.
D)they differ only in the configuration around one carbon atom.
E)they rotate plane-polarized light in the same direction.

Question 11

Which of the following is not a reducing sugar?

A)Fructose
B)Glucose
C)Glyceraldehyde
D)Ribose
E)Sucrose

Question 12

Which of the following statements about hydrogen bonding in glycogen and cellulose is true?

A)Glycogen forms more internal H-bonds than cellulose.
B)Extensive internal hydrogen bonding makes cellulose more water soluble than glycogen.
C)Extensive hydrogen bonding with water makes cellulose more soluble than glycogen.
D)Glycogen primarily forms hydrogen bonds within a single chain.
E)The hydrogen bonding in cellulose favors a helical conformation.

Question 13

Which of the following monosaccharides is not a carboxylic acid?

A)6-Phospho-gluconate
B)Gluconate
C)Glucose
D)Glucuronate
E)Muramic acid

Question 14

The basic structure of a proteoglycan consists of a core protein and a:

A)glycolipid.
B)glycosaminoglycan.
C)lectin.
D)lipopolysaccharide.
E)peptidoglycan.

Question 15

Which of the following pairs is interconverted in the process of mutarotation?

A)d-glucose and d-fructose
B)d-glucose and d-galactose
C)d-glucose and d-glucosamine
D)d-glucose and l-glucose
E)( $\alpha$ -d-glucose and $\beta$ -d-glucose)

Question 16

Starch and glycogen are both polymers of:

A)fructose.
B)glucose1-phosphate.
C)sucrose.
D)( $\alpha$ -d-glucose.)
E)( $\beta$ -d-glucose.)

Question 17

Which of the following is a heteropolysaccharide?

A)Cellulose
B)Chitin
C)Glycogen
D)Hyaluronate
E)Starch

Question 18

Which of the following statements about starch and glycogen is false?

A)Amylose is unbranched;amylopectin and glycogen contain many ( $\alpha$ 1 $\rightarrow$ 6)branches.
B)Both are homopolymers of glucose.
C)Both serve primarily as structural elements in cell walls.
D)Both starch and glycogen are stored intracellularly as insoluble granules.
E)Glycogen is more extensively branched than starch.

Question 19

d-Glucose is called a reducing sugar because it undergoes an oxidation-reduction reaction at the anomeric carbon.One of the products of this reaction is:

A)d-galactose.
B)d-gluconate.
C)d-glucuronate.
D)d-ribose.
E)muramic acid.

Question 20

Which of following is an anomeric pair?

A)d-glucose and d-fructose
B)d-glucose and l-fructose
C)d-glucose and l-glucose
D)( $\alpha$ -d-glucose and $\beta$ -d-glucose)
E)( $\alpha$ -d-glucose and $\beta$ -l-glucose)

Question 21

(a)Define "reducing sugar."
(b)Show the reaction product of glucose after it is used as a reducing sugar.
(c)Explain why fructose is also considered a reducing sugar.(Hint: It must first undergo a chemical conversion. )
(d)Sucrose is a disaccharide composed of glucose and fructose
(Glc( $\beta$ 1 $\rightarrow$ 2)Fru).Explain why sucrose is not a reducing sugar,even though both glucose and fructose are.

Question 22

Which of the following statements concerning sialic acid residues on glycoproteins is true?

A)Sialic residues on erythrocytes are recognized by lectins,leading to removal of the erythrocytes.
B)Sialic residues on ceruloplasmin are recognized by lectins,leading to removal of ceruloplasmin.
C)Sialic residues are removed by neuraminidases.
D)The anti-viral drug oseltamavir accelerates the removal of sialic acid residues.
E)Both A and B above

Question 23

The biochemical property of lectins that is the basis for most of their biological effects is their ability to bind to:

A)amphipathic molecules.
B)hydrophobic molecules.
C)specific lipids.
D)specific oligosaccharides.
E)specific peptides.

Question 24

In glycoproteins, the carbohydrate moiety is always attached through the amino acid residues:

A)asparagine,serine,or threonine.
B)aspartate or glutamate.
C)glutamine or arginine.
D)glycine,alanine,or aspartate.
E)tryptophan,aspartate,or cysteine.

Question 25

Why is it surprising that the side chains of tryptophan residues in lectins can interact with sugars?

A)Because the side chain of tryptophan is hydrophilic and sugars are hydrophobic
B)Because the side chain of tryptophan is (-)charged and sugars are generally (+)charged or neutral
C)Because the side chain of tryptophan can make hydrogen bonds and sugars cannot.
D)Because the side chain of tryptophan is hydrophobic and sugars are generally hydrophilic
E)None of the above

Question 26

Which of the following is not a reason that it is difficult to study oligosaccharide composition from biological systems?

A)Oligosaccharides are often branched.
B)Oligosaccharides often have a high negative charge density.
C)Oligosaccharides have a variety of linkages .
D)Oligosaccharides have too much conformational flexibility.
E)There are no specific glycosidase enzymes that can be used to selectively digest oligosaccharides.

Question 27

Which of the following statements about heparan sulfate is not true?

A)Sulfation of heparan sulfate to form NS domains is important for its role as an anti-coagulant.
B)Heparan sulfate can promote protein-protein interactions via the NS domains.
C)The secondary structure of heparan sulfate is completely random.
D)The NA domains of heparan sulfate contain no sulfation.
E)The core repeating structure of heparan sulfate is made up of alternating GlcNAc and GlcA.

Question 28

Define each in 20 words or fewer:
(a)anomeric carbon
(b)enantiomers
(c)furanose
(d)pyranose
(e)glycoside
(f)epimers
(g)aldose
(h)ketose

Question 29

The number of structurally different polysaccharides that can be made with 20 different monosaccharides is far greater than the number of different polypeptides that can be made with 20 different amino acids if both polymers contain an equal number (say 100)of total residues.Explain why.

Question 30

Categorize each of the following as an aldose,a ketose,or neither.

Question 31

Which of the following techniques is not commonly used to study oligosaccharide structures?

A)X-ray crystallography
B)Matrix-assisted laser desorption/ionization mass spectroscopy (MALDI-MS)
C)Nuclear magnetic resonance (NMR)
D)Complete chemical synthesis
E)Oligosaccharide microarrays

Question 32

In the following structure: (a)How many of the monosaccharide units are furanoses and how may are pyranoses?
(b)What is the linkage between the two monosaccharide units?
(c)Is this a reducing sugar?

Question 33

This compound is l-glyceraldehyde.Draw a stereochemically correct representation of C-1 and C-2 of d-glucose.

Question 34

Explain why all mono- and disaccharides are soluble in water.

Question 35

Which of the following is a dominant feature of the outer membrane of the cell wall of gram negative bacteria?

A)Amylose
B)Cellulose
C)Glycoproteins
D)Lipopolysaccharides
E)Lipoproteins

Question 36

Explain how it is possible that a polysaccharide molecule,such as glycogen,may have only one reducing end,and yet have many nonreducing ends.

Question 37

Describe one biological advantage of storing glucose units in branched polymers (glycogen,amylopectin)rather than in linear polymers.

Question 38

(a)Draw the structures of both anomers of glucose in the pyranose ring form.
(b)How many asymmetric carbons (chiral centers)does each of these structures have?
(c)How many stereoisomers of the glucose are theoretically possible?

Question 39

Match these molecules with their biological roles.
(a)glycogen __ viscosity,lubrication of extracellular secretions
(b)starch __ carbohydrate storage in plants
(c)trehalose __ transport/storage in insects
(d)chitin __ exoskeleton of insects
(e)cellulose __ structural component of bacterial cell wall
(f)peptidoglycan __ structural component of plant cell walls
(g)hyaluronate __ extracellular matrix of animal tissues
(h)proteoglycan __ carbohydrate storage in animal liver

Question 40

In measuring long-term glucose levels in the bloodstream,glycated hemoglobin must be separated from unmodified hemoglobin to determine the percentage of glycated hemoglobin.Suggest a simple chromatographic method by which this separation can be performed.

Question 41

Identify all the epimeric pairs in the structures shown below.

Question 42

Briefly explain the procedure involved in using an oligosaccharide microarray to identify the binding specificity for a potential lectin.

Question 43

Describe the process by which "old" serum glycoproteins are removed from the mammalian circulatory system.

Question 44

Sketch the principal components of a typical proteoglycan,showing their relationships and connections to one another.

Question 45

How do oligosaccharide portions of glycoproteins change the properties of the proteins?

Question 46

What are lectins? What are some biological processes that involve lectins?

Question 48

Describe the structure of a proteoglycan aggregate such as is found in the extracellular matrix.

Question 49

What is the biological advantage to an organism that stores its carbohydrate reserves as starch or glycogen rather than as an equivalent amount of free glucose?

Question 50

Explain in molecular terms why humans cannot use cellulose as a nutrient,but goats and cattle can.

Question 51

Briefly explain how the drugs Tamiflu and Relenza work to prevent the flu.

Question 52

Draw the structure of the repeating basic unit of (a)amylose and (b)cellulose.

Question 53

Describe the differences between a proteoglycan and a glycoprotein.

Question 54

The glycosaminoglycans are negatively charged at neutral pH.What components of these polymers confer the negative charge?