biochem test 3 Flashcards

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1

Polysaccharides cannot be used by cells:

a. as fuel storage molecules.

b. for structural elements in cell walls.

c. for structural elements in animal exoskeletons.

d. for the extracellular matrix in animal cells.

e. All of the answers are correct.

e

2

_____ is the systematic characterization of all carbohydrate components of a given cell or tissue.

a. Genomics
b. Proteomics
c. Glycomics
d. Metabolomics

e. Lipidomics

c

3

In a(n) _____, the carbonyl group is at the end of the carbon chain, but in a(n) _____, the carbonyl group can be at any other position.

a. aldose; ketose

b. ketose; aldose

c. hexose; heptose

d. aldose; hexose

e. ketose; tetrose

a

4

Which is the MOST plausible reason why most hexoses of living organisms are D isomers?

  1. D isomers are more energetically favorable.
  2. D isomers are also used by amino acids. – L amino acids are used to synthesize proteins
  3. Sugars must be opposite isomers from amino acids. – both sugars and amino acids can be D and L conformations, if there is a stereogenic center there are D and L enantiomers
  4. Evolving enzymes were made to remain with an initial preference.
  5. Evolving enzymes switch preference often to find the best isomer.

d

5

Which answer choice is the BEST description of the benefits that are provided by the extended conformation that the heteropolysaccharide glycosaminoglycans assume in solution?

  1. The repulsive forces of densely packed negative charges are minimized.
  2. The hydrophobic portions of the molecules may pack closely together to maximize van der Waals forces.
  3. The patterns of sulfated and nonsulfated sugar residues are more easily recognized by their respective ligands.
  4. The repulsive forces of densely packed negative charges are minimized, and the hydrophobic portions of the molecules may pack closely together to maximize van der Waals forces.
  5. The repulsive forces of densely packed negative charges are minimized, and the patterns of sulfated and nonsulfated sugar residues are more easily recognized by their respective ligands.

e

6

Which monosaccharide is NOT a hexose?

a. fructose

b. ribose

c. mannose

d. glucose

e. galactose

b

7

Which statement is NOT true regarding phosphorylated sugar?

a. It is trapped inside the cell.

b. It is relatively stable at neutral pH.

c. It is activated for subsequent chemical transformation. This is true it is destabilized for further reactions.

d. It can be a component of a nucleotide.

e. All of the statements are true.

e

8

When drawing a Haworth perspective formula from a Fisher projection, which statement is true regarding anomers?

  1. It is α if the hydroxyl group on the anomeric carbon is up.
  2. It is α if the hydroxyl group on the anomeric carbon is down.
  3. It is α if the hydroxyl group on the anomeric carbon is on the same side of the ring as the C-6.
  4. It is α if the hydroxyl group on the anomeric carbon is on the opposite side of the ring as the C-6.
  5. None of the answers is correct.

d

9

Which disaccharide has an anomeric carbon available for oxidation?

a. Glc(α1↔1α)Glc

b. Glc(α1↔2β)Fru
c. Fru(β2↔1α)Glc
d. both Glc(α1↔2β)Fru and Fru(β2↔1α)Glc

e. None of the answers is correct.

e

10

During which process are chemical bonds NOT broken?

a. mutarotation

b. interconverting between two configurations

c. interconverting between two conformations

d. interconverting between two anomers

e. None of the answers is correct: all involve breaking a chemical bond.

c

11

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

  1. The glycogen sample is more soluble than the cellulose sample.
  2. The cellulose sample is more soluble than the glycogen sample.
  3. Both samples consist of a mixture of α-D-glucose and β-D-glucose.
  4. The glycogen sample has a higher ratio of α-D-glucose than the cellulose sample.
  5. The cellulose sample contains only β-D-glucose.

c

12

Which modification cannot be made to a sugar molecule by an organism?

a. oxidation of the carbonyl carbon
b. replacing a hydroxyl group with an amino group
c. oxidizing a carbon atom to a carboxyl group

d. replacing a hydroxyl group with a hydrogen atom

e. All of the answer choices are possible sugar derivatives.

e

13

Which is a heteropolysaccharide?

a. cellulose

b. chitin
c. glycogen
d. glycosaminoglycan

e. starch

d

14

Which statement about dextrans is false?

a. Dextrans are bacterial extracellular adhesives.
b. Dextrans can be branched.
c. Dextrans can have (α1→3) and (α1→6) linkages.
d. Dextrans are heteropolysaccharides.

e. All of the statements are true.

d

15

Which factor is NOT a part of determining the complete structure of an oligosaccharide or polysaccharide?

a. determination of linear sequence

b. determination of lectin partners

c. determination of branching positions
d. determination of glycosidic linkages
e. determination of monosaccharide configuration

b

16

Which statement about cellulose is true?

  1. Cellulose is the main storage polysaccharide of animal cells.
  2. Cellulose is a highly branched polysaccharide.
  3. Cellulose is a homopolysaccharide.
  4. Cellulose glucose residues contain the same configuration as amylose glucose residues.
  5. Cellulose cannot be broken down by invertebrate animals.

c

17

Which polysaccharide is NOT a homopolysaccharide?

a. glycogen

b. chitin
c. amylose
d. hyaluronan – part of the feather complex

e. dextran

d

18

Which glycosaminoglycan is found in the synovial fluid of joints?

  1. chondroitin sulfate
  2. dermatan sulfate
  3. hyaluronan
  4. keratin sulfate
  5. heparan sulfate

c

19

The polysaccharide chitin is MOST chemically similar to:

  1. cellulose.
  2. dextran.
  3. glycogen.
  4. starch.
  5. amylose.

a

20

Which pair are NOT digestible by vertebrates?

  1. cellulose and amylose
  2. amylose and glycogen
  3. cellulose and chitin
  4. chitin and amylopectin
  5. amylose and amylopectin

c

21

In amylose, the MOST stable structure is a _____, which is stabilized by _____.

  1. coiled helix; interchain hydrogen bonds
  2. coiled helix; interchain covalent branching
  3. coiled helix; hydrogen bonds to surrounding water molecules
  4. straight, extended chain; interchain hydrogen bonds
  5. straight, extended chain; hydrogen bonds to surrounding water molecules

a

22

The hydrogen bonding in cellulose has what effect?

  1. Extensive intrachain and interchain hydrogen bonding yields a low water content in cellulose.
  2. The hydrogen bonding yields cellulose chains that make straight, stable supramolecular fibers.
  3. Hydrogen bonding gives cellulose a high tensile strength.
  4. Hydrogen bonding enables cellulose to perform well as plant cell walls.
  5. All of the answers are correct.

e

23

Which statement about starch and glycogen is false?

  1. Amylose is unbranched; amylopectin and glycogen contain many (α1 → 6) branches.
  2. Both are homopolymers of glucose.
  3. Both serve primarily as structural elements in cell walls.
  4. Both starch and glycogen are stored intracellularly as insoluble granules.
  5. Glycogen is more extensively branched than starch.

c

24

Which statement about hydrogen bonding in glycogen and cellulose is true?

  1. Glycogen forms more internal hydrogen bonds than cellulose.
  2. Extensive internal hydrogen bonding makes cellulose more water soluble than glycogen.
  3. Extensive hydrogen bonding with water makes cellulose more soluble than glycogen.
  4. Glycogen is stabilized by interchain hydrogen bonds.
  5. The hydrogen bonding in cellulose favors a helical conformation.

d

25

In most cases, in order for an informational carbohydrate to become a biologically active molecule it must:

  1. be an asymmetric molecule.
  2. contain a reducing sugar.
  3. contain an O-glycosidic bond.
  4. be covalently joined to a protein or lipid.
  5. be present in the extracellular matrix.

d

26

Several types of human joint and skeletal defects are a result of a defect in a biosynthetic enzyme responsible for synthesis of:

  1. glycosaminoglycans.
  2. glycoproteins.
  3. glycolipids.
  4. lipopolysaccharides.
  5. glycosphingolipids.

a

27

Which statement about heparan sulfate is NOT true?

  1. Sulfation of heparan sulfate to form NS domains is important for its role as an anticoagulant.
  2. Heparan sulfate can promote protein-protein interactions via the NS domains.
  3. The secondary structure of heparan sulfate is completely random.
  4. The NA domains of heparan sulfate contain no sulfation.
  5. The core repeating structure of heparan sulfate is made up of alternating GlcNAc and GlcA.

c

28

Which type of protein interaction is NOT one with the NS domains of heparan sulfate?

  1. conformational activation
  2. cell-surface localization/concentration
  3. enhanced protein-protein interaction
  4. binding extracellular signaling molecules
  5. All of the answer choices are types of protein interaction with heparan sulfate.

e

29

Which statement accurately describes the interactions between the molecules thrombin, antithrombin, and heparan sulfate?

  1. In the absence of heparan sulfate, antithrombin binds tightly to thrombin, inhibiting blood coagulation.
  2. In the absence of heparan sulfate, antithrombin cannot bind to thrombin, inhibiting blood coagulation.
  3. In the presence of heparan sulfate, antithrombin binds tightly to thrombin, inhibiting blood coagulation.
  4. In the presence of heparan sulfate, antithrombin cannot bind to thrombin, enabling blood coagulation.
  5. In the presence of heparan sulfate, antithrombin binds tightly to thrombin, enabling blood coagulation.

c

30

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

  1. glycolipid.
  2. glycosaminoglycan.
  3. lectin.
  4. lipopolysaccharide.
  5. peptidoglycan.

b

31

Which statement is false regarding proteoglycans?

  1. Both syndecans and glypicans can be shed into the extracellular space.
  2. Proteoglycan shedding is unregulated in cells.
  3. A protease or phospholipase is responsible for releasing proteoglycans.
  4. Proteoglycan shedding is activated in cancerous cells.
  5. Cell features such as proteoglycans can be changed quickly.

b

32

Oligosaccharides differ from nucleic acids and proteins in that oligosaccharides are commonly:

  1. branched.
  2. polymeric.
  3. acidic.
  4. basic.
  5. None of the answers is correct.

a

33

Under what circumstance might an organism's patterns of glycosylation NOT be altered?

  1. development
  2. genetic diseases
  3. cancer
  4. cell differentiation
  5. All of the answers are correct.

e

34

_____ are secreted or membrane proteins that contain large numbers of O-linked oligosaccharide chains.

a. Gangliosides

b. Mucins

c. Glycins
d. Aminoglycans
e. Immunoglobulins

b

35

_____ could be used to determine human blood group type.

a. Lipopolysaccharides
b. Gangliosides
c. Glycoproteins

d. Lipoproteins

e. Mucins

b

36

Which description of a ganglioside is MOST accurate?

  1. the dominant surface feature of gram-negative bacteria
  2. the dominant surface feature of gram-positive bacteria
  3. an oligosaccharide chain attached to a newly synthesized protein in the ER
  4. a membrane lipid in which the polar head group is a complex oligosaccharide containing at least one sialic acid
  5. a membrane lipid in which the oligosaccharide is attached to a mucin

d

37

About what percentage of mammalian proteins are glycosylated?

a. 5%

b. 15%

c. 50%

d. 90%

e. 95%

c

38

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.

a

39

Which compound(s) is a dominant feature of the outer membrane of the cell wall of gram-negative bacteria?

  1. amylose
  2. cellulose
  3. glycoproteins
  4. lipopolysaccharides
  5. lipoproteins

d

40

Which statement is NOT a reason that it is difficult to study oligosaccharide composition from biological systems?

  1. Oligosaccharides are often branched.
  2. Oligosaccharides often have a high charge density.
  3. Oligosaccharides have a variety of linkages (e.g., α1→6 or β1→4).
  4. Glycosaminoglycan oligosaccharides have extremely stable sulfate esters.
  5. There are no specific glycosidase enzymes that can be used to selectively digest oligosaccharides.

d

41

A glycoconjugate may include a carbohydrate as well as a(n):

  1. amino acid.
  2. lipid.
  3. saccharide.
  4. protein or lipid.
  5. amino acid, a lipid, or a saccharide.

d

42

_____ are secreted or membrane proteins that contain large numbers of O-linked oligosaccharide chains.

a. Gangliosides
b. Mucins
c. Glycins
d. Aminoglycans
e. Immunoglobulins

b