Test 3C

Question 1

1. Which of the following is not a reason why collagen fibrils form extracellulary rather than intracellulary during the biosynthesis and transport of collagen from the endoplasmic reticulum through the Golgi apparatus to the cell surface
   a. Type 1 procollagen cannot form the triple helical oligomers that are the core structure of any collagen oligomer
   b. Type 1 procollagen contains hydroxylated proline and lysine residues that prevent polypeptide chain oligomerization within the cell
   c. Procollagen must be soluble and small enough to fit within the intracellular transport machinery
   d. Type 1 procollagen synthesized in cells contains nonhelical segments at each end of the polychain that limit their ability to oligomerize into collagen fibrils

Answer 1

a. Type 1 procollagen cannot form the triple helical oligomers that are the core structure of any collagen oligomer

Question 2

2. A major function of tight junctions is to
   a. Create a strong adherence between cells
   b. Promote the intermixing of proteins between the apical and basolateral surfaces of cells
   c. Sort cells on the basis of adhesion during cell migration in embryos
   d. Seal the space between adjacent cells to provide, for example, a barrier to sugar diffusion across an epithelial cell layer

Answer 2

d. Seal the space between adjacent cells to provide, for example, a barrier to sugar diffusion across an epithelial cell layer

Question 3

3. In hemidesmosomes, integrins are indirectly linked to
   a. Lamin-rich intermediate filaments within the nucleus
   b. Microtubules
   c. Actin microfilaments
   d. Cytoplasmic intermediate filaments

Answer 3

d. Cytoplasmic intermediate filaments

Question 4

4. Homophilic interactions between cells involve interactions between
   a. Adhesion molecules of different molecular classes
   b. Between integrins and ICAMs
   c. Cadherins and -catenin
   d. Adhesion molecules of the same molecular class

Answer 4

d. Adhesion molecules of the same molecular class

Question 5

5. The major function of adhesion proteins such as fibronectin is to
   a. Link collagen, proteoglycans, and cells containing integrins
   b. Support communication between adjacent cells
   c. Link epithelial cell layers
   d. Seal cell layers at tight function

Answer 5

a. Link collagen, proteoglycans, and cells containing integrins

Question 6

6. ____, although structurally different from gap junctions in animal cell tissues, may be thought of as the functional equivalent of gap junctions in plants
   a. hemidesmosomes
   b. desmosomes
   c. plasmadesmata
   d. adherens junctions

Answer 6

c. plasmadesmata

Question 7

7. the cell-cell interactions mediated by the selectins, integrins, and most members of the Ig superfamily are ___ interactions in which the cytoskeletons of adjacent cells are not linked to one another
   a. nonspecific
   b. stable
   c. physiologically unimportant
   d. transient

Answer 7

d. transient

Question 8

8. proteins of the ___ family link transmembrane proteins of the tight junctions to actin
   a. catenin
   b. plakin
   c. zonula occludens
   d. plectin

Answer 8

c. zonula occludens

Question 9

9. cellulose, chitin, and hyaluronan are all deposited extracellulary by
   a. ABC transporters
   b. Transmembrane enzyme complexes
   c. Exocytosis
   d. Secretion

Answer 9

b. Transmembrane enzyme complexes

Question 10

10. Which of the following statements about collagen is false?
    a. It is the most abundant protein in animal tissues
    b. It forms a double helix, with two collagen molecules wrapped around one another in a ropelike structure
    c. It contains an amino acid called hydroxyproline
    d. It is a secreted protein

Answer 10

b. It forms a double helix, with two collagen molecules wrapped around one another in a ropelike structure

Question 11

11. The major transmembrane proteins in tight junctions include all of the following except
    a. Thrombospondin
    b. Occludin
    c. Claudin
    d. JAM

Answer 11

a. Thrombospondin

Question 12

12. The junctions between animal cells that allow the free passage of molecules smaller than approximately 1000 daltons are called
    a. Hemidesmosomes
    b. Gap junctions
    c. Tight junctions
    d. Plasmodesmata

Answer 12

b. Gap junctions

Question 13

13. The basic structural polysaccharide of fungal cell walls, crab shells, and insect exoskeletons is
    a. Chitin
    b. Collagen
    c. Hemicellulose
    d. Cellulose

Answer 13

a. Chitin

Question 14

14. Primary plant cells walls are cross-linked by
    a. Lignin
    b. Turgin
    c. Pectin
    d. Hemicellulose

Answer 14

c. Pectin

Question 15

15. Adherens junctions and desmosomes may be distinguished from each other on the basis of
    a. The linkage of cadherins either to actin filaments or to intermediate filaments
    b. Whether the linkage is between two cells or between a cell and the extracellular environment
    c. The presence of cadherins versus ICAMs
    d. Whether the cadherins are linked directly or indirectly to the cytoskeletal elements

Answer 15

a. The linkage of cadherins either to actin filaments or to intermediate filaments

Question 16

16. Adherens junctions link to cytoplasmic
    a. Actin filaments
    b. Intermediate filaments
    c. Microtubules
    d. Myosin filaments

Answer 16

a. Actin filaments

Question 17

17. Which of the following signal molecules binds to nuclear receptors?
    a. Thyroid hormone
    b. Vitamin D3
    c. Retinoic acid
    d. Steroid
    e. All of the above

Answer 17

e. All of the above

Question 18

18. What is the difference between Gram-positive and Gram-negative bacteria?
    a. Gram-positive bacteria make gramicidin A and Gram-negative bacteria do not
    b. Gram-positive bacteria are motile and Gram-negative are not
    c. Gram-positive bacteria are surrounded by a single membrane and Gram-negative by two membranes, with an inner membrane that is porous to small molecules and ions
    d. Gram-positive bacteria are surrounded by a single membrane, whereas Gram-negative bacteria are surrounded by a double membrane, with an outer membrane that is porous to ions and small molecules

Answer 18

d. Gram-positive bacteria are surrounded by a single membrane, whereas Gram-negative bacteria are surrounded by a double membrane, with an outer membrane that is porous to ions and small molecules

Question 19

19. Animal cells are embedded in a(n)
    a. Extracellular matrix
    b. Hemicellulose-rich hyaluronan layer
    c. Pectin-rich basal lamina
    d. Cell wall

Answer 19

a. Extracellular matrix

Question 20

20. Integrins link extracellular matrix proteins either directly or indirectly to all of the following intracellular proteins except
    a. Talin
    b. Laminin
    c. Actin
    d. -actinin

Answer 20

b. Laminin

Question 21

21. fibrous structural proteins of the extracellular matrix are embedded in gels formed from polysaccharides called
    a. fibronectin
    b. glycosaminoglycans (GAGs)
    c. elastin
    d. laminin

Answer 21

b. glycosaminoglycans (GAGs)