U2L5 Membrane Transport

Multiple Choice

A cell biologist is performing a membrane transport experiment. The biologist observes the movement of molecules into the cell by transporting proteins. However, energy is not being used. Which of the following best describes what the biologist is observing?

• Passive transport is being observed because the molecules were moving into the cell.

• Active transport is being observed because molecules are being transported by transport proteins.

• Simple diffusion is being observed because the molecules were moving from a high concentration to a low concentration.

• Facilitated diffusion is being observed because transport proteins are being activated without the use of energy.

Open Ended

The figure below illustrates a membrane in the digestive system. During digestion, fructose has to be moved into the cells of the small intestine. The image illustrates the transport of fructose across the membrane of cells of the small intestine. What process we learned about today illustrates the transport of fructose molecules into the intestinal cells? State the type and transport and explain your reasoning for picking it.

Open Ended

(a) Identify the processes A, B, C, and D.

(b) Describe each of the transport processes mentioned above. (Describe each as active or passive transport)

(c) Explain how the structure of the plasma membrane affects the movement of specific molecules across the membrane in each case.