When analyzing a sample of cells from a patient, you find the lysosomes are filled with undigested material. This observation makes you think that the lysosomes are not functioning properly. What are three different defects that could be responsible for malfunctioning lysosomes?

Most of the proteins that enter the nucleus possess a nuclear localization signal (NLS), even if they are small enough to pass through the nuclear pore complex unhindered. Why would a small protein have an NLS, when it naturally diffuses across the nuclear pore complex without one?

The eukaryotic cytoskeleton is a highly dynamic network of filaments and motor proteins. Which of the following correctly describe activities of these cytoskeletal components? Select True or False for each statement.

T/FMyosin motors walk toward the plus ends of intermediate filaments.

T/FDynein motors are responsible for the whip-like movement of eukaryotic flagella.

T/FKinesin motors move vesicles along tracks toward the microtubule-organizing center.

T/FActin filaments are required for cytoplasmic streaming.

Cells that line your intestines are known to possess a large number of membrane proteins that transport small molecules and ions across the plasma membrane. Which of the following cell structures would you expect to be required for this characteristic of the cells?

a. The endoplasmic reticulum

b. Peroxisomes

c. Lysosomes

d. The cell wall

George Palade's research group used the pulse–chase assay to elucidate the secretory pathway in pancreatic cells. If they had instead performed this assay on muscle cells, where would you expect the labeled proteins to end up during the chase?

(Muscle cells consist primarily of actin and myosin filaments and have high energy demands for muscle contraction.)