Essential Cell Biology 5th edition

Questions
733
KEY TERMS
adherens junction
apical
basal
basal lamina
cadherin
cancer
cell junction
cell wall
cellulose microfibril
collagen
connective tissue
desmosome
differentiated cell
embryonic stem (ES) cell
epithelium (plural epithelia)
extracellular matrix
fibroblast
fibronectin
gap junction
genetic instability
glycosaminoglycan (GAG)
hemidesmosome
induced pluripotent stem (iPS) cell
integrin
metastasis
oncogene
organoid
plasmodesma
(plural plasmodesmata)
pluripotent
proteoglycan
proto-oncogene
stem cell
tight junction
tissue
tumor suppressor gene
Wnt protein
QUESTIONS
QUESTION 20–9
Which of the following statements are correct? Explain your
answers.
A. Gap junctions connect the cytoskeleton of one cell to
that of a neighboring cell or to the extracellular matrix.
B. A wilted plant leaf can be likened to a deflated bicycle
tire.
C. Because of their rigid structure, proteoglycans can
withstand a large amount of compressive force.
D. The basal lamina is a specialized layer of extracellular
matrix to which sheets of epithelial cells are attached.
E. Epidermal cells in the skin are continually shed and are
renewed every few weeks; for a tattoo to be long-lasting,
it is therefore necessary to deposit pigment below the
epidermis.
F. Although stem cells are not differentiated, they are
specialized in the sense that they give rise only to specific
cell types.
QUESTION 20–10
Which of the following substances would you expect to
spread from one cell to the next through (a) gap junctions
and (b) plasmodesmata: glutamic acid, mRNA, cyclic AMP,
Ca 2+ , proteins, and plasma membrane phospholipids?
QUESTION 20–11
Discuss the following statement: “If plant cells contained
intermediate filaments to provide the cells with tensile
strength, their cell walls would be dispensable.”
QUESTION 20–12
Through the exchange of small metabolites and ions, gap
junctions provide metabolic and electrical coupling between
cells. Why, then, do you suppose that neurons communicate
primarily through chemical synapses (as shown in Figure
12−40) rather than through gap junctions?
QUESTION 20–13
Gelatin is primarily composed of collagen, which is
responsible for the remarkable tensile strength of
connective tissue. It is the basic ingredient of jello; yet,
as you probably experienced many times yourself while
consuming the strawberry-flavored variety, jello has virtually
no tensile strength. Why?
QUESTION 20–14
“The structure of an organism is determined by the genome
that the fertilized egg contains.” What is the evidence on
which this statement is based? Indeed, a friend challenges
you and suggests that you replace the DNA of a stork’s egg
with human DNA to see if a human baby results. How would
you answer him?
QUESTION 20–15
Leukemias—that is, cancers arising through mutations that
cause excessive production of white blood cells—have an
earlier average age of onset than other cancers. Propose an
explanation for why this might be the case.
QUESTION 20–16
Carefully consider the graph in Figure 20−43, which shows