41) Facilitated diffusion is similar to simple diffusion because:

A) each requires the use of energy.

B) each requires a protein channel for movement to occur.

C) in both, materials move down their concentration gradient.

D) each utilizes vesicles to move material around the cell.

42) The sodium-potassium pump is an example of:

A) passive transport.

B) receptor-mediated endocytosis.

C) facilitated diffusion.

D) active transport.

43) Calcium ions (Ca2+) are present in the endoplasmic reticulum at concentrations 1,000 times higher than in the cytosol (the gel-like part of the cell outside organelles). One protein on the endoplasmic reticulum membrane is devoted to allowing Ca2+ to move from the endoplasmic reticulum to the cytosol, and another protein moves Ca2+ from the cytosol to the endoplasmic reticulum. These processes are not trivial–Ca2+ released into the cytosol allows, for example, for muscle contraction and communication between nerve cells. In this pair of Ca2+ transport proteins, you would predict that the protein moving Ca2+ from the endoplasmic reticulum to the cytosol ________, and the protein that moves Ca2+ from cytosol to the endoplasmic reticulum ________.

A) transports calcium slowly; transports calcium rapidly

B) works without ATP; requires ATP

C) requires ATP; works without ATP

D) is large; is small

E) is small; is large

44) Yeast cells take up glucose (a sugar) to use as their primary source of energy. Typically, glucose concentrations outside yeast cells are far lower than glucose concentrations inside the cells. Therefore, for yeast to take up glucose, the cells must use:

A) facilitated diffusion to move glucose down its concentration gradient.

B) active transport to move glucose up its concentration gradient.

C) facilitated diffusion to move glucose up its concentration gradient.

D) active transport to move glucose down its concentration gradient.

E) osmosis to directly absorb glucose.

45) All of the following processes bring materials into a cell except:

A) endocytosis.

B) receptor-mediated endocytosis.

C) exocytosis.

D) phagocytosis.

46) Phagocytosis is a type of ________ in which a cell engulfs another cell.

A) passive transport

B) active transport

C) facilitated diffusion

D) endocytosis

E) exocytosis

47) Insulin and many other hormones are protein molecules. Based on your knowledge of transport processes, you can say that cells that secrete these types of hormones do so through:

A) facilitated diffusion.

B) pinocytosis.

C) passive diffusion.

D) receptor-mediated endocytosis.

E) exocytosis.

48) The 1985 Nobel Prize in Physiology or Medicine was awarded to Michael Brown and Joseph Goldstein for their work on cholesterol metabolism. Brown and Goldstein investigated the cause of remarkably high levels of circulating cholesterol found in certain families. Just as remarkable was the high incidence of heart disease in these families. What Brown and Goldstein found was not what might be expected–these individuals did not make too much cholesterol. Instead, most of these people had defects in receptor-mediated endocytosis (RME). What could possibly link high cholesterol levels in the blood and defective RME in these patients?

A) Cholesterol was being secreted from cells by RME at too high a rate and therefore accumulated in the blood.

B) Cholesterol was not transported into cells by RME and therefore accumulated in the blood.

C) Cholesterol was being secreted by facilitated diffusion at too high a rate and therefore accumulated in the blood.

D) Cholesterol was not transported into cells by active transport proteins and therefore accumulated in the blood.

E) Cholesterol was not transported into cells by facilitated diffusion and therefore accumulated in the blood.