Chapter 8

What do cyclic sugars have

Cyclic sugars have two anomeric forms; the a-anomer and B-anomer

Which configuration (D or L) are much more biologically abundant?

D molecules are much more abundant

Which feature of the bacterial peptidoglycan is not essential for its structural stability? L-amino acids such as lysine. D-monosaccharides. D-amino acids. N-acetylmuramic acid.

D-monosaccharides.

What are enantiomers

Enantiomers are pair of molecules that are mirror images of each other. For carbohydrates, this means that all of the sterocenters are opposite from one anther

What are polysaccharides known as

Glycans

What does the structure of glycogen allow for

Glycogen's highly branched structure , which has many nonreducing ends permits the rapid mobilzation of glucose in times of metabolic need

What is one important trait that glycoproteins have

Glycoproteins exhibit a trait called microheterogeneity. This is a result of the variable carbohydrate composition. This variability does not effect the funciton of the glycoprotein

How are carbohydrate chains generated in glycoproteins

In glycoproteins, the carbohydrate chains are enzymatically generated and covalently linked to the polypeptide without the rigid guidance of nucleic acid templates.

What is the only molecule that can simultaneously have all five of its non-H substituents in equitorial positions.

Only B-D-glucose

Bacterial cell walls are composed of _____. pectin chondroitin sulfate chains peptidoglycans heparin proteoglycans

Peptidoglycans

What holds the chains in cellulose together

Stacks of these sheets are held together by hydrogen bonds and van der Waals interactions

Which carbon is the anomeric carbon

The anomeric carbon is the carbon derived from the carbonyl carbon (the ketone or aldehyde funcional group)

What happens to the anomers in an aqueous solution

The anomers freely interconvert in aqueous solution so at equilibrium, the mixture of B-anomer is 63.6% while the a-anomer is 36.4%

What is fundamental to carbohydrates biological activity

The apparently haphazard arrangements of carbohydrates on proteins and on the surfaces of cells are the key to recognition events between proteins and between cells.

A saccharide that has free aldehyde group is called a(n) _____________. ketose nonreducing sugar reducing sugar aldohexose alditol

reducing sugar

Which of the following statements applies to all artificial sweeteners? Artificial sweeteners cannot be readily metabolized. Artificial sweeteners are peptides and provide important amino acids. Artificial sweeteners have fewer calories than sucrose. Artificial sweeteners are much sweeter than sucrose. All of the above.

Artificial sweeteners are much sweeter than sucrose.

N-linked oligosaccharides can be covalently linked to proteins at which amino acid? Gly Ser Glu Tyr Asn

Asn

Which of the following sequences represents a recognition site for N-linked glycosylation where X is any amino acid except Pro? Gln—X—Ser His—X—Ser Arg—X—Ser Asn—X—Ser Asp—X—Ser

Asn—X—Ser

What is the most common monosaccharide in nature

B-D-glucose

What are bacterial cell walls made from

Bacterial cell walls are made from peptidoglycans

What is responsible for bacteria's virulence

Bacterial cell walls are responsible for their virulence.

How many stereoisomers are possible for an aldopentose such as ribose? 2 4 8 16 32

8 aldopentose=> aldehyde with 5 carbon atoms. The first and last carbon atoms are c=0,H and CH2OH respectively. Therefore we have three sterocenters, each with two possible configurations. This leads to 2^(3), where two is the possible configurations and 3 is the number of sterocenters

What do secreted proteins and membrane-associated proteins have in common

Almost all of the secreted and membrane-associated proteins of eukaryotic cells are glycosylated

What does a glycosidic bond do

A glycosidic bond links the anomeric carbon to other compounds

What would a ketohexose look like

A ketohexose would have a total of 6 carbon atoms and would have a ketone group at the second carbon

How many stereoisomers are possible for a ketopentose such as ribulose? 2 4 8 16 32

A ketopentose has a ketone group at one of the carbons. This leads to three carbon atoms that are not able to have sterocenters as C1and C5 have formulas of CH2OH and C2 has a formula of C=O. Therefore there are only two sterocenters, each with two possible configurations. This leads to 2^(2) where the first 2 is the number of configurations and the second 2 is the number of sterocenters.

What is a reducing sugar

A reducing sugar is any sugar that is cpable of acting as a reducing agent because it has a free aldehyde group or free ketone group to react.

What type of sugars are reducing sugars

All monosaccharides are reducing sugars, along with some disaccharides, oligosaccharides and polysaccharides

In terms of structure, what is the main difference between a-amylose and amylopectin? a-Amylose has only one reducing end. a-amylose is a linear polymer with a-(1->6) glycosidic linkages, but amylopectin has a-(1->4) glycosidic linkages. Both contain a-(1->4) glycosidic linkages of D-glucose, but amylopectin also has a-(1->6) branches. a-amylose is a linear polymer with a-(1->4) glycosidic linkages, but amylopectin ias a linear polymer of a-(1->6) glycosidic linkages.

Both contain a-(1->4) glycosidic linkages of D-glucose, but amylopectin also has a-(1->6) branches.

Which of the following does not accurately describe glycosylation sites of proteins? On the surfaces of proteins In loops or turns Asn, Ser, or Thr residues Buried residues inside proteins

Buried residues inside proteins

What are the most abundant biological molecules

Carbohydrates

How are carbohydrates different from proteins and nucleic acids

Carbohydrates do not catalyze complex chemical reactions as do proteins, nor do carbohydrates replicate themselves as do nucleic acids

What molecule accounts for over half of the carbon in the biosphere

Cellulose

What are the structural polysaccharides

Cellulose and Chitin are structrual polysaccharides

What is the structure of cellulose fibers

Cellulose chains are flat ribbons in which successive glucose rings are turned over 180 degrees with respect to each other

In terms of structure, which of the following is the main difference between cellulose and chitin? Cellulose is formed by β-(1->4) glycosidic bonds, while chitin is formed by a-(1->4) glycosidic bonds. Cellulose is linear, but chitin is branched. Cellulose is a linear polymer of D-glucose, but chitin is a linear polymer of N-acetyl-D-glucosamine. Cellulose is neutral, but chitin is negatively charged.

Cellulose is a linear polymer of D-glucose, but chitin is a linear polymer of N-acetyl-D-glucosamine. Both also have β-(1->4) linkages

What is cellulose

Cellulose is a linear polymer of up to 15,000 D-glucose residues linked by B(1-4) glycosidic bonds

In terms of structure, what is the main difference between -amylose and cellulose? Cellulose is formed by β-(1->4) glycosidic bonds, but α-amylose is formed by a-(1->4) glycosidic bonds. Cellulose is a linear polymer of D-glucose, but a-amylose is a linear polymer of D-allose. Cellulose is linear, but a-amylose is branched. Cellulose is branched, but -amylose is a linear polymer.

Cellulose is formed by β-(1->4) glycosidic bonds, but α-amylose is formed by a-(1->4) glycosidic bonds. They are both polymers of D-glucose, and differ only in the anomeric form used.

What is chitin

Chitin is a homopolymer of B(1-4)-linked N-acetyl-D-glucosamine resideues. Differs chemically from cellulose only in that each C2-OH group is replaced by an acetamido function.

What are epimers

Epimers are two isomers with different configurations of atoms around ONE of several asymetirc carbon atoms present. For carbohydrates this means that the molecules are identical except around one sterocenter

Which statement about stereoisomers is false? D- and L-isomers are mirror images of each other. Epimers can interconvert rapidly in solution. Anomers freely interconvert in solution through a linear intermediate. Some hexoses can interconvert between pyranose and furanose forms.

Epimers can interconvert rapidly in solution.

What does the identification of sugar as nonreducing produce evidence of

Evidence that it is a glycoside

Alcohols react with the carbonyl groups of aldehydes and ketons to form what

Forms hemiacetals and hemiketals

A sugar with a five-membered ring is called what

Furanose

How do you determine galactose

Galactose in an aldohexos and therefore has four sterocenters. The configuration of the sterocenters starting from the top of the molecule goes D-L-L-D.

What do gram negative bacteria have

Gram negative bacteria have a thin cell wall (about 30A) covered by a complex outer membrane. Outer membrane functions in part to exclude sunbstances toxic to the bacterium including the gram stain

What do gram positive bacteria have

Gram positive bacteria have cell walls that are thicker than 250A surrounding their plasma membrane

What does Hyaluronat do

Hyaluronate (also known as Hyaluronic acid ) acts as a shock absorber and is an important glycosaminoglycan component of connective tissue

What occurs in N-linked oligosaccharides

In N-linked oligosaccharides, GlcNAc is invariably B-linked to the amide nitrogen of an Asn residue in the sequence of Asn-X-Ser or Asn-X-Thr

What happens in O-linked oligosaccharides

In O-linked oligosaccharides, B-galactosyl-(1-3)-a-N-acetylgalactosamine is linked to the OH group of of either Ser or Thr

What is an amino sugar

In an amino sugar, one or more of the OH groups have been replaced by an amino group which is often acetylated.

What is an anomer

In carbohydrate chemistry, an anomer is a special type of epimer. It is one of two stereoisomers of a cyclic saccharide that differs only in its configuration at the hemiacetal/acetal carbon, also called the anomeric carbon.

What is a heteropolysaccharide

In general, heteropolysaccharides (heteroglycans) contain two or more different monosaccharide units. Although a few representatives contain three or more different monosaccharides, most naturally occurring heteroglycans contain only two different ones and are closely associated with lipid or protein.

What does the symbol (1-4) combined with the B prefix indicate

Indicates that the B anomer links C1 of a sugar to the O4 of another sugar

Which statement about the ABO blood group antigens is false? Individuals of Type O blood have the H antigen and both anti-A and anti-B antibodies. These antigens occur at the nonreducing ends of the oligosaccharide component of glycolipids. These antigens differ because of the activity of a specific glycotransferase. Individuals of Type A blood have both the A antigen and anti-A antibodies.

Individuals of Type A blood have both the A antigen and anti-A antibodies.

What is the structure of a-amylose

It forms a left-handed helix

What will happen to a solution of pure -D-glucopyranose? It will convert completely to the linear form. It will begin converting to the -anomer, eventually reaching an equilibrium concentration of 63.6 %. It will remain in solution, as is. It will convert completely to the more stable anomer, -D-glucopyranose.

It will begin converting to the -anomer, eventually reaching an equilibrium concentration of 63.6 %.

What does the oxidation of of an aldose yield

It's aldehyde group is converted to a carboxylic acid group (COOH), yielding an aldonic acid

What elements are carbohydrates made from

Just three elements; carbon, hydrogen an oxygen combined according to the formula (C*H2O)n where n=>3

Which one of the following steps found in N-linked glycosylation is also part of O-linked glycosylation? A 14-unit oligosaccharide is attached to the protein. Monosaccharides are added while the protein is in the Golgi apparatus. Some of the sugars are removed during processing. A 3-residue sequence pattern in the protein determines the sites of glycosylation

Monosaccharides are added while the protein is in the Golgi apparatus.

What are the bonds that link D-ribose to purines and pyrimidines in nucleic acids

N-glycosidic bonds. Form between the anomeric carbon and an amine

When does N-linked glycosylation occur

N-linked glycosylation occurs cotranslationally, that is, while the peptide is being synthesided

Where does N-linked glycosylation occur

N-linked glycosylation occurs in the endoplasmic reticulum while the protein is being synthesized by a ribosome

Are furanose and pyranose planar

NO

How are oligosaccharides attached to proteins

Oligosaccharides are covalently attahced to proteins by either N-glycosidid or O-glycosidic bonds

Where are oligosaccharides usually found on proteins

Oligosaccharides are usually attached to proteins at sequences that form surface loops or tuns

How are polysaccharides different from proteins and nucleic acids

Polysaccharids form branched as well as linear polymers. This is becuase glycosidic linkages can be made to any of the hydroxyl groups of a monosaccharide

What are proteoglycans

Proteoglycans are a diverse set of macromolecues that result from the aggregation of proteins and glycosaminoglycans in the extracellular matrix

What is the structure of Proteoglycans

Proteoglycans have a bottlebrush-like molecular architecture with "bristels" noncovalently attached to a filamentus hyaluronate "backbone"

A sugar with a six-membered ring is called what

Pyranonse

What is the structure of ribose

Ribose is an aldopentose with all D configurations at the sterocenters

What is starch

Starch is a heteropolysaccharide composed of a-amylose and amylopectin

Which of the following is the most abundant disaccharide? lactose cellulose a-amylose maltose sucrose

Sucrose

What is the most abundant disaccharide and is it a reducing sugar

Sucrose; not a reducing sugar. Anomeric carbon of each sugar participates in the glycosidic bond.

Which is not a structural component of peptidoglycan? Sulfate Disaccharide Pentaglycine Tetrapeptide

Sulfate

Where are O-linked oligosaccharides synthesided

Synthesized in the Golgi appartus by the serial addition of monosaccharide units to a complted polypeptide chain

At equilibrium in solution, D-glucose consists of a mixture of its anomers. Which statement most accurately describes this solution? The solution consists of approximately equal amounts of the a- and B-anomers. The straight-chain form is present in high concentration. The a-anomer is more stable and is slightly preferred over the B-anomer. The B-anomer predominates over the a-anomer by a ratio of approximately 2:1. None of the answers above is correct.

The B-anomer predominates over the a-anomer by a ratio of approximately 2:1. The B-anomer is more stable than the a-anomer.

Difference between the a-anomer and the B-anomer

The a-anomer has the hydroxyl group on the opposite side of C6 while the B-anomer has the hydroxyl group on the same side as C6

Where does the assignment of D or L configuration come from

The assignment of D or L configuration comes from orientation of the asymmetric center furthest from the the carbonyl group. For D configurations, the asymmetric center farthest from the the carbonyl group must have the OH located on the right. For L configuration, the asymmetric center farthest from the carbonyl group must have the OH located on the left side.

Which chair conformation predominates

The confirmation that predominates is the one in which the bulkiest ring substituents occupy equitorial positions rather than the more crowded axial positions.

What is the difference between a-amylose and cellulose

The differ in their bond configurations, leading to very different structural properties. Cellulose has B(1-4) linkages while a-amylose contains a(1-4) bonds. Cellulose forms a tightly packed, fully extended conformation while a-amylose's a-glycosidic bonds cause it to adopt an irregularly aggregating helically coiled conformation.

Which of the following is not part of the systematic naming of an oligosaccharide? The anomeric configuration of each monosaccharide. The enzymes necessary for synthesis of the oligosaccharide. A description of the linkage between monosaccharides. The identity of each monosaccharide.

The enzymes necessary for synthesis of the oligosaccharide.

Where are glycosaminoglycans found and what is their structure

The extracellular spaces, particularly those of connective tissues such as cartilage, tendon, skin and blood vessel walls contain collaagen and other proteins embedded in a el-like matrix that is composed largely of glycosaminoglycans. These unbranched polysaccharides consist of alternating uronic acid and hexosamine residues.

What are the main storage polysaccharides

The main storage polysaccharides are Starch and Glycogen.

What can the pyranose ring do that the furnaose ring cannot

The pyranose ring like the cyclohexane ring, can assume a chair conformation, in which the substituents of each atom are arranged tetrahedrally

What are the most common aldoses

The six-carbon sugars glucose, mannose and galactose.

Which carbon determines the D-L stereochemical designation

The sterocenter carbon atom furthest from the aldehyde or ketone

What does the storage of glucose as starch do?

The storage of glucose as starch greatly reduces the large intracellular osmotic pressure that would result from its storage in monomeric form because somotic pressure is proportional to the number of solute molecules in a given volume

Which of the following statements about glycosaminoglycans is strictly true? They contain one or more sulfate groups per disaccharide. They are highly hydrated, negatively charged linear polymers. They have repeating units of disaccharides. They are made from modified galactose monosaccharides.

They are highly hydrated, negatively charged linear polymers.

In which way are saccharides similar to amino acids? They are formed from three elements, C, H, and O. Their polymers are not made from a template. They can be joined covalently to form polymers. They do not form polymers capable of catalysis.

They can be joined covalently to form polymers.

What is the structure of Amylopectin

This molecule consists mainly of a(1-4) linked glucose residues but is a branched molecule with a(1-6) branch points every 24 to 30 glucose residues

What is microheterogeneity

Variation in the chemical structure of substances that does not produce major changes in its properties

When does a sugar have a L configuraiton

When the carbon sterocenter furthest from the anomeric ketone/aldehyde functional group has an OH on the LEFT HAND SIDE

When does a sugar have a D configuration

When the carbon sterocenter furthest from the anomeric ketone/aldehyde functional group has an OH on the RIGHT HAND SIDE

Are sugars removed during this process

Yes, some sugars are removed during processing, but additional monosaccharide residues are added by the specifc action of glycosyltrnasferases in the golgi aoparatus

What does the treatment of aldoses and ketoses with NaBH4 yield.

Yields alditols. The aldehyde now takes the formula CH2OH

What does the oxidation of the primary alcohol group of aldoses yield

Yields uronic acid. The primary alcohol group is the alcohol group opposite the aldehyde group (at opposite end of molecule)

Cellulose is a linear copolymer of glucose and galactose. a branched polymer of glucose. a linear polymer of glucose with β(1-4) linkages. a linear polymer of glucose with a(1-4) linkages. sometimes called starch.

a linear polymer of glucose with β(1-4) linkages.

Which polysaccharide is found in a helically coiled conformation? chitin a-amylose cellulose lignin none of the above

a-amylose

Starch is a mixture of a-amylose and amylopectin. glycogen and amylopectin. glycogen and a-amylose. glycogen and cellulose. a-amylose and maltose.

a-amylose and amylopectin

What is a-amylose

a-amylose is a linear polymer of several thousand glucose residues linked by a(1-4) bonds.

What are the derivatives of monosaccharides

aldonic acids, uronic acids, alditols, deoxy sugars and amino sugars

Which of these polysaccharides is a branched polymer? chitin amylose cellulose amylopectin hyaluronic acid

amylopectin

The transformation of a monosaccharide into its ______ occurs easily and does not require the assistance of a catalyst. epimer anomer sugar alcohol diastereomer none of the above

anomer Readily transfer between a and B when in solution. B is more prominent than a

The sialic acids are important constituents of glycoproteins and glycolipids. are N-acetyl glucosamine derivatives. incorporate a succinic acid derivative. all of the above none of the above

are important constituents of glycoproteins and glycolipids.

Which of the following polysaccharides cannot be digested by mammalian salivary, gastric, or pancreatic enzymes? amylopectin amylose chitin glycogen starch

chitin

Glycoproteins are only found in bacteria. are extremely homogeneous. are typically less than 1% carbohydrate by weight. are assembled under strict genetic control. exhibit microheterogeneity.

exhibit microheterogeneity.

The bonding of alcohols to the anomeric center of a carbohydrate results in the formation of a(n) __________ bond. anomeric amide glycosidic ester hydrogen

glycosidic

Alcohols react with aldehydes to form hemiketals. lactones. lactams. glycosides. hemiacetals.

hemiacetals.

Which of the following is an example of a heteropolysaccharide? cellulose chitin starch glycogen hyaluronic acid

hyaluronic acid

What is the difference between the a-anomer and the the b-anomer

in the a-anomer, the OH substituent of the anomeric carbon is on the opposite side of the sugar ring from the CH2OH group at the chiral center that designates the D or L configuration. in the B-anomer, the OH substituent of the anomeric carbon is on the opposite side of CH2OH group of the chiral center that designates the D or or L configuration.

Proteins that bind to specific carbohydrates are called ______. pectins oligonucleotides glycosaminoglycans lectins chitins

lectins

Which of these is not an artificial sweetener? saccharine aspartame maltose acesulfame alitame

maltose

Which of the following is a disaccharide? amylose saccharin aspartame amylopectin none of the above

none of the above

Chitin differs from cellulose due to inversion of configuration at the anomeric carbon. sulfonation of the C2—OH group. a much greater prevalence of branching. replacement of the C2—OH group by an acetamido group. replacement of the C6—OH group by an amino group.

replacement of the C2—OH group by an acetamido group.

Which of the following is a mixture of two types of polymers? cellulose starch chitin glycogen amylose

starch

O-linked oligosaccharides are commonly attached to the —OH group of _____. ribose tyrosine lysine threonine glycine

threonine