Carbohydrates: Structure, and Function Flashcards by Geno Sadaya | Brainscape

Q

The most abundant biomolecule on earth

A

Carbohydrates

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Q

All carbohydrates have the empitical formula (CH2O)n. T/F

A

F

Some also contain nitrogen, phosphorus, or sulfur

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Q

Most abundant monoscaccharide in nature

A

D-glucose or dextrose

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Q

All common monosaccharides and disaccharides have names ending with the suffix “-ose.” T/F

A

T

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Q

Polysaccharides have 20 or more monosaccharide units. T/F

A

T

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Q

What’s the difference between an aldose and a ketose?

A

An aldose has its carbonyl group at the end of the carbon chain while a ketose has it at any other position

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Q

The simplest monosaccharides

A

Glyceraldehyde and dihydrooxyacetone

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Q

All monosaccharides contain one or more chiral carbons. T/F

A

F

Dihydroxyacetone is the one exception.

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Q

How is D isomer and L isomer differentiated?

A

Look for the chiral carbon furthest from the carbonyl group. If the hydroxyl group attached to it is on the left, it is an L isomer; if on the right, a D isomer.

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Q

In the Fischer projection, to which direction of projection do the horizontal and the vertical bond represent?

A

Horizontal : toward the reader Vertical: away from the reader

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Q

Most of the hexoses of living organisms are which enantiomer?

A

D isomer

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Q

Which monosaccharide does not have a chiral carbon?

A

Dihydroxyacetone

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Q

Which of the following sugars is an aldohexose?

A. Erythrose

B. Arabinose

C. Fructose

D. Mannose

A

D

Erythrose is an aldotetrose; Arabinose is an aldopentose; Fructose is a ketohexose.

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Q

What is the process by which alpha and beta forms of D-glucose interconvert in aqueous solutions?

A. Mutarotation

B. Enolization

C. Racemization

D. Isomerization

A

A

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Q

Which of the following is the characteristic feature of sugar enantiomers?

A. One would be a pyranose, the other a furanose

B. They are mirror images of each other

C. They differ by the orientation of one hydroxyl group

D. One exists in the boat conformation, the other in the chair conformation

A

B

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Q

d-glyceraldehyde and dihydroxyacetone

a. Anomer
b. Epimer
c. Aldose Ketose Pair

A

C

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Q

d-glucose and d-mannose

a. Anomer
b. Epimer
c. Aldose Ketose Pair

A

B

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Q

d-galactose and d-glucose

a. Anomer
b. Epimer
c. Aldose Ketose Pair

A

B

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Q

d-ribose and d-ribulose

a. Anomer
b. Epimer
c. Aldose Ketose Pair

A

C

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Q

d-a-glucose and d-b-glucose

a. Anomer
b. Epimer
c. Aldose Ketose Pair

A

A

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Q

The smallest of monosaccharides contain “n=3”,meaning in (CH2O)3. Called trioses, these cannot be further hydrolysed to more simpler sugars. Which of the following is NOT a triose?

A. D-glucose

B. Dihydroxyacetone

C. D-glyceraldehyde

D. L-glyceraldehyde

A

A

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Q

Glucose undergoes mutarotation in solution. Which of the following is the MOST predominant isomeric form of glucose in solution?

A. Alpha-glucopyranose

B. Beta-glucopyranose

C. Alpha-glucofuranose

D. Beta-glucofuranose

A

B

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Q

Which is true about glucose?

a) it is a ketohexose
b) it is an enantiomer of mannose
c) it results from hydrolysis of lactose
d) its preferred and most stable conformation is Haworth projection

A

C

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Q

Classify according to number of carbons:

D -Fructose

A

Hexose

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Q

Aldose?

D -Fructose

D -Galactose

D- Glucose

D- Glyceraldehyde

D - Erythrulose

Dihydroxyalcetone

L - Xylose

L - Ribose

D - Ribulose

A

D -Galactose

D- Glucose

D- Glyceraldehyde

L - Xylose

L - Ribose

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Q

D-galactose and D-mannose are epimers. T/F

A

F

They are epimers of glucose, but not epimers of each other.

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Q

D-glucose and D-galactose are epimers at which carbon?

A

C-4

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Q

D-glucose and D-mannose are epimers at which carbon?

A

C-2

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Q

What are epimers?

A

Sugars that differ only in the configuration around one carbon atom

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Q

How are carbons of a sugar numbered?

A

C-1 begins at the end of the chain nearest the carbonyl group

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Q

Tetroses have ring conformations in aqueous solution. T/F

A

F Only sugars with 5 or more carbons form rings in aqueous solution.

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Q

Sugars with eight carbons are called octose. T/F

A

F

There are no sugar with 8 carbons

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Q

Reducing sugars oxidise this ion

A

Cupric (Cu^2+)

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Q

Bond that joins disaccharides

A

O-Glycosidic bond

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Q

Glycosidic bonds are readily hydrolyzed by base but resist cleavage by acid. T/F

A

F

They are hydrolyzed by acid but resist cleavage by base

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Q

When the anomeric carbon of a sugar is involved in a glycosidic bond, that sugar residue cannot take the linear form and therefore becomes a reducing sugar. T/F

A

F

It becomes a non-reducing sugar. Oxidation of a sugar by a cupric ion occurs only when sugar is in linear form.

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Q

Is maltose a reducing sugar or non-reducing? Why?

A

Reducing,

it has a free anomeric carbon

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Q

Monosaccharide components of maltose

A

Two D-glucose molecules

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Q

Monosaccharide components of lactose

A

D-galactose and D-glucose

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Q

Monosaccharide components of sucrose

A

Glucose and fructose

Q

Reducing or non-reducing: Maltose Lactose Sucrose

A

Maltose: Reducing

Lactose: Reducing

Sucrose: Non-reducing

Q

Haworth perspective is linear or cyclic?

A

Cyclic

Q

Polysaccharides are also called glycans. T/F

A

T

Q

Glucose polymers in starch

A

Amylose and amylopectin

Q

What is/are fxns of the glycosaminoglycans?

A. extra cellular matrix material

B. membrane receptors

C. anticoagulants

D. all of the above

E. A and B only

A

D

Q

What is true of sugars?

a. They contain polyhydroxyl functional groups making them hydrophobic.
b. They mainly function as an energy source for the cell.
c. The sugar molecules can form biopolymers by a hydrolytic reaction.
d. Most common form in the cell is sucrose.

A

B

Q

Which is the most stable conformation that the sugar above can form?

a. Fisher projection
b. Haworth projection
c. Chair
d. Boat
e. Envelope

A

C

Q

Which of the following carbohydrates does not contain glucose as a structural unit?

a. Lactose
b. Mannose
c. Sucrose
d. Maltodextrin
e. Cellulose

A

B

Q

Which of the following is/are epimer/s of glucose?

a. Galactose
b. Fructose
c. Mannose
d. A and B only
e. A and C only

A

E

Q

Which of the following is NOT an aldohexose?

a. Galactose
b. Glucose
c. Fructose
d. Mannose

A

C

Q

Which of the following BEST describes the structure of glycogen?

a. Glucose in α (1,6) linkages and α (1,4) branches
b. Glucose in α (1,4) linkages and α (1,6) branches
c. Glucose in α (1,4) linkages and β (1,6) branches
d. Glucose in β (1,4) linkages and α (1,6) branches

A

B

Q

What is the principal difference between amylose and cellulose?

a. Amylose is found internally in plant cells while cellulose makes up the cell wall.
b. Amylose is a branched polysaccharide while cellulose is unbranched/linear.
c. Amylose has α (1,4) glycosidic linkages while cellulose has β (1,4) linkages.
d. There is an enzyme in man that digests amylose but none for cellulose.

A

C

Q

Which of the following is NOT a monosaccharide derivative?

a. Amygdalin
b. Mucin
c. Sorbitol
d. D-glucosamine
e. D-glucuronic acid

A

B

Q

Which of the following is NOT a component of a proteoglycan?

a. Glycosaminoglycan
b. Protein core
c. Trisaccharide link composed of Gal-Gal-Xyl
d. Disaccharide link composed of an acidic and an amino sugar

A

D

Q

Which of the following glycosidic bonds is NOT typical of glycoproteins?

a. O-linked if the glycosidic bond is between a carbohydrate and threonine
b. O-linked if the glycosidic bond is between a carbohydrate and serine
c. O-linked if the glycosidic bond is between a carbohydrate and tyrosine
d. N-linked if the glycosidic bond is between a carbohydrate and asparagines

A

C

Q

Which glycosaminoglycan is responsible for increasing the viscosity of the synovial fluid?

a. Chondroitin sulfate
b. Dermatan sulfate
c. Heparan sulfate
d. Hyaluronic acid
e. Keratan sulfate

A

D

Q

Which is the prevalent glycosaminoglycan in basement membranes and also associated with cell surfaces?

a. Chondroitin sulfate
b. Dermatan sulfate
c. Heparan sulfate
d. Hyaluronic acid
e. Keratan sulfate

A

C

Q

Which of the following interactions do NOT contribute to intermolecular binding which involves carbohydrates?

a. Adhesion of leukocytes to endothelial cells
b. Binding of antibody to antigen
c. Clumping of red blood cells
d. Binding of a macrolide antibiotic to its intracellular target
e. Sperm cell recognition of egg cells of their own species

A

C

Q

What carbohydrate disease is related to phosphorylation?

a. Glycogen storage disease
b. Lactose intolerance
c. Diabetes
d. Fructosemia

A

A

Q

Which of the following holds true for both glycogen and amylopectins?

a) Both are storage forms of glucose in animal cells
b) Both serve as dietary fibers
c) Both have branching after every 8-10 residues
d) Both contain glucose in α-1-4 and α-1-6 glycosidic linkages

A

D

Q

Why is glycogen the known storage form of carbohydrates?

a) highly branched
b) highly compacted
c) able to store high amounts of energy
d) all of the above

A

D

Q

N- and O- glycosidic linkages help in naming disaccharides, oligo- and polysaccharides. Which of the following is INCORRECT of regarding glycosidic linkages?

A. Lactose contains an O-glycosidic beta 1,4 bond.

B. Amylopectin and glycogen have similar O-glycosidic linkages as well as function.

C. Both cellulose and amylopectin have alpha 1,6 bonds forming branched chains.

D. The beta linkage in cellulose is not digestible by mammalian enzymes.

A

C

Q

Which of the following is the basic repeating unit of chitin?

A. Alpha-D-glucopyranose

B. N-acetyl-D-glucosamine

C. N-acetyl-D-galactosamine

D. Beta-D-glucofuranose

A

B

Q

Which of the following statements is INCORRECT about glycosaminoglycans?

A. Glycosaminoglycans do not exist in free form.

B. Hyaluronic acid consists of disaccharide units of N-acetylglucosamine and glucuronic acid.

C. Hyaluronic acid molecules appear coiled like a helix.

D. Hyaluronic acid’s hydrophilic carboxylate groups of glucuronic acid residues bind calcium ions.

A

A

Q

Which of the following areas has the LEAST amount of hyaluronic acid?

A. Vitreous body of the eye

B. Joints and skin

C. Heart valves

D. Liver

A

D

Q

Glycogen

A. RBCs

B. Sialic acid

C. Stored in liver

D. Inulin

E. Dextrin

A

C

Q

What is the difference between amylose and amylopectin?

a. Amylose is a linear polymer of glucose linked by alpha 1-6 bonds
b. Amylose is a branched polymer of glucose linked by alpha 1-4 bonds
c. Amylose is not branched
d. Amylose is branched
e. Amylose is much larger than amylopectin

A

C

Q

Which is NOT a homopolysaccharide?

A. Inulin

B. Heparin

C. Cellulose

D. Amylose

A

B

Q

Which glycosidic bonds are present in glycogen?

A. a(1,6) linkages in the linear chain, a(1,4) at the branches

B. a(1,4) linkages in the linear chain, a(1,6) at the branches

C. b(1,4) linkages in the linear chain, a(1,6) at the branches

D. a(1,4) linkages in the linear chain, b(1,6) at the branches

A

B

Q

Which of the following is NOT true for glycogen and amylopectin?

A. Both are storage forms of glucose

B. Both are homopolysaccharides

C. Both are branched polymers of glucose

D. Branching occurs every 8-10 residues in both

A

D

Q

Why can’t humans utilize cellulose as source of energy?

A. It is very insoluble

B. It has no nutritive value

C. The bacterial enzyme that degrades cellulose is not present in the human gut

D. The acidic pH in the stomach inactivates the enzyme responsible for its digestion

A

C

Q

Which is not a component of a proteoglycan?

a. repeating disaccharide unit composed of an acidic and an amino group
b. polysaccharide chains covalently bound to a protein core
c. N-glycosidic bond between sugar and asparagine
d. trisaccharide link composed of Gal-Gal-Xyl

A

C

Q

What is the main structural difference between proteoglycans and glycoproteins?

a. the sugar moieties in proteoglycans does not form glycosidc bonds
b. N-glycosidic bonds are only present in glyco proteins
c. the protein part serves as anchor to the plasma membrane
d. there are more protein than sugar units in glycoprotein’s than in proteoglycans

A

D

Q

carbohydrate-related disease; deficiency of phosphorylation enzyme

a. glycogen storage disease
b. lactose intolerance
c. diabetes mellitus
d. fructosuria

A

D

Q

Which of the ff molecular interactions does NOT involve carbohydrates?

a. Roleaux formation
b. Adhesion of leukocytes to endothelial cells
c. Sperm cell recognition of egg cell
d. Binding of an aminogylcoside antibiotic to its cellular target

A

A

Q

Which of the following biomolecules DOES NOT have a sugar moiety?

a. ATP
b. NADH
c. Sphingosine
d. Mucin

A

C

Q

Sorbitol

A. Enzymatic oxidation

B. Linkage of amino group

C. Reduction of carbonyl group

D. Covalent interaction of sugar and alcohol

A

D

Q

Which of the following carbohydrates in the peptidoglycan layer is unique to the bacterial cell wall?

A. N-acetyl glucosamine

B. N-acetyl galactosamine

C. N-acetyl muramic acid

D. N-acetyl neuraminic acid (Sialic acid)

A

C

Q

Which statement describes how beta-lactam antibiotics manifest their action against certain bacteria?

A. They bind to the D-alanyl-D-alanine enzyme catalytic site

B. They intercalate between peptidoglycan monomers

C. They prevent transpeptidation of peptidoglycan units

D. They prevent translocation of peptidoglycan subunits to the cell exterior.

A

A

Q

What is the role of the oligosaccharide moieties in the different blood groups?

A. binds cells to the endothelial lining

B. serves as antigenic determinant

C. prevents RBC clumping

D. enables intercellular communication

A

B

Q

A

A
B
D

Q

A

A
B
C
D

Q

A

C
A
B
D

Q

ABO antigen

A. RBCs

B. Sialic acid

C. Stored in liver

D. Inulin

E. Dextrin

A

D

Q

Glomerular filtration rate

A. RBCs

B. Sialic acid

C. Stored in liver

D. Inulin

E. Dextrin

A

A

Q

Formed by hydrolyzing starch

A. RBCs

B. Sialic acid

C. Stored in liver

D. Inulin

E. Dextrin

A

E

Q

Important component of gangliosides

A. RBCs

B. Sialic acid

C. Stored in liver

D. Inulin

E. Dextrin

A

B

Q

Sialic Acid

A. Enzymatic oxidation

B. Linkage of amino group

C. Reduction of carbonyl group

D. Covalent interaction of sugar and alcohol

A

B

Q

Glucuronic Acid

A. Enzymatic oxidation

B. Linkage of amino group

C. Reduction of carbonyl group

D. Covalent interaction of sugar and alcohol

A

A

Q

Classify according to number of carbons:

D -Galactose

A

Hexose

Q

Classify according to number of carbons:

D- Glucose

A

Hexose

Q

Classify according to number of carbons:

D- Glyceraldehyde

A

Triose

Q

Classify according to number of carbons:

D - Erythrulose

A

Tetrose

Q

Classify according to number of carbons:

Dihydroxyalcetone

A

Triose

Q

Classify according to number of carbons:

L - Xylose

A

Pentose

Q

Classify according to number of carbons:

Sialic acid

L - Ribose

A

Nonose

Q

Classify according to number of carbons:

L - Ribose

A

Pentose

Q

Ketose?

D -Fructose

D -Galactose

D- Glucose

D- Glyceraldehyde

D - Erythrulose

Dihydroxyalcetone

L - Xylose

L - Ribose

D - Ribulose

A

D -Fructose

D - Erythrulose

Dihydroxyalcetone

D - Ribulose