Facilitated Diffusion Across a Biological Membrane

Ansewer some questions

example questions:

1. Facilitated diffusion across a biological membrane requires and moves a substance

its concentration gradient.

a. energy and transport proteins … down; b. energy … down; c. transport proteins … down; d. energy and transport proteins … against; e. transport proteins … against

2. In lab, you use a special balloon that is permeable to water but not sucrose to make an “artificial cell.” The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. Which of the following will occur?

a. Water will leave the balloon; b. Water will enter the balloon; c. Sucrose will leave the balloon; d. Sucrose will enter the balloon; e. none of the choices will occur.

3. Some protozoans have special membrane-bound bodies called contractile vacuoles that continually eliminate excess water from the cell. The presence of these membrane-bound bodies tells you that the environment

a. is isotonic to the protozoan; b. is hypotonic to the protozoan; c. is hypertonic to the protozoan; d. contains a higher concentration of solutes than the protozoan; e. none of the choices are correct.

4. Which one of the following processes could result in the net movement of a substance into a cell, if the substance is more concentrated in the cell than in the surroundings?