EXTRA QUESTIONS

Receptor-mediated endocytosis is the mechanism for transport of

• all macromolecules.

• cholesterol.

• ions.

• integral membrane proteins.

• clathrin.

cholesterol

Phagocytosis, pinocytosis, and receptor-mediated endocytosis all involve

• the intake of large particles. the export of macromolecules.

• the intake of specific fluids by the cell.

• invagination of the plasma membrane.

• the presence of receptor proteins.

• invagination of the plasma membrane.

Lactose is transported via secondary active transport into bacterial cells. Which of the following would be absent from a diagram illustrating the mechanism of this transport system?

• Diffusion of a substance in the same direction as its concentration gradient

• The movement of lactose against its concentration gradient

• The formation of a concentration gradient

• Coupling of lactose transport to transport of another substance

• The direct use of ATP to transport lactose

The direct use of ATP to transport lactose

In many bacteria Fé3+ is required at cellular concentrations that are much higher than that of the surrounding environment. How does a bacterium respond to this challenge?

• By creating more Fe'+ carrier proteins to increase diffusion rates across the cell membrane

• By using the Fe'+ concentration gradient to generate ATP

• By consuming ATP to move Fe3+ against its concentration gradient

• By using an Fe3+ ion antiporter rather than a symporter

• By relying on facilitated diffusion to transport Fe3+ across the membrane

By consuming ATP to move Fe3+ against its concentration gradient

If a cell has an increased need for a particular molecule already present in a higher concentration within the cell than in the extracellular fluid, the cell might use active transport, which usually moves molecules

• toward higher pH.

• in the same direction as diffusion moves them.

• in a direction opposite to the one in which diffusion moves them.

• in a direction that tends to bring about equilibrium.

• from inside to outside the cell.

• in a direction opposite to the one in which diffusion moves them.

You have isolated a yeast strain with a genetic mutation that increases the hydrophobie nature of the transmembrane domains of one of its ion channels. What is the most probable outcome?

• The diffusion rate of the ion across the membrane will increase.

• Less energy will be required to move the ion across the membrane.

• More energy will be required to move the ion across the membrane.

• The diffusion rate of the ion across the membrane will decrease.

• lon channel specificity will change to allow different ions across the membrane.

The diffusion rate of the ion across the membrane will decrease.

Integrins are transmembrane proteins that can reversibly link the cytoskeleton of a cell to the extracellular matrix.

When there is a period during which there are cycles of this linkage being made and broken, made and broken, the result may be

• increased communication through gap junctions.

• more stability provided to the cytoskeleton.

• decreased diffusion of water into the cell.

• cell movement through the extracellular matrix.

• the binding of integrins to form tight junctions.

cell movement through the extracellular matrix.

unsaturated fatty acids are more

fluid than saturated