Macrophage cells undergo a process called phagocytosis in which material is brought into a cell in the form of membrane vesicles and then transported along microtubules toward the cell center. assuming that the centrosome is near the cell center, you can predict that these vesicles are moving to the end of microtubules using the motor protein

a. minus end; dynein
b. plus end; kinesin
c. minus end; kinesin
d. plus end; dynein

The correct answer is: A. minus end; dynein

Microtubules are cytoskeletal fibers that have an important role in the intracellular transport (movement of vesicles within the cell) and in the mitotic spindle during mitosis. The plus end of the microtubules extend through the periphery of the cells while the minus ends are anchored within the centrosome.

Necessary proteins for the vesicle’s movement are motor proteins:

•kinesin  which is positive end directed

•  dynein which is negative end directed

So, beside vesicles these proteins are also involved in organelles’ transport in opposite directions through the cytoplasm.

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.