Use the Following to Answer the Following Questions -Which of the Following Makes It Necessary for Animal Cells

Multiple Choice

Use the following to answer the following questions. All three are involved in maintenance of cell shape.
$\begin{array}{c}\begin{array}{|l}\hline\\ \text {Property}\\\hline\\\\ \text {Structure}\\\hline\\ \text {Diameter}\\\hline \text {Main}\\\text {functions}\\\hline \end{array}\begin{array}{|l|}\hline \text { Microtubules (tubulin}\\\text { polymers) }\\\hline \text {Hollow tubes; wall}\\ \text {consists of 13 columns}\\ \text {of tubulin molecules}\\\hline \text {\( 25 \mathrm{~nm} \) with 15-nm}\\ \text {lumen}\\\hline\\ \text {Cell motility}\\\hline \end{array}\begin{array}{l|}\hline \text { Microfilaments (actin}\\ \text { filaments) }\\\hline \text { Two intertwined strands}\\ \text { of actin, each a polymer }\\ \text { of actin subunits}\\\hline\\ \text { \( 7 \mathrm{~nm} \) }\\\hline\\ \text { Cell motility}\\\hline \end{array}\begin{array}{l|}\hline \text {Intermediate}\\ \text {filaments}\\\hline \text {Fibrous proteins }\\ \text {supercoiled into}\\ \text { thicker cables}\\\hline\\ \text {8-12nm}\\\hline\\ \text {Anchorage}\\\hline\end{array}\end{array}$

-Which of the following makes it necessary for animal cells, although they have no cell walls, to have intercellular junctions?

A) Cell membranes do not distinguish the types of ions and molecules passing through them.
B) Large molecules, especially proteins, do not readily get through one, much less two adjacent cell membranes.
C) Cell-to-cell communication requires physical attachment of one cell to another.
D) Maintenance of connective tissue shape requires cells to adhere to one another.
E) The relative shapelessness of animal cells requires a mechanism for keeping the cells aligned.