Question

potassium ions play an important role in maintaining normal cell functions. potassium ions are positively charged. like carbon dioxide, potassium ions can cross the cell membrane by passive transport. unlike carbon dioxide, potassium ions enter the cell passively using facilitated diffusion. this video shows the facilitated diffusion of potassium ions. the diffusion of potassium ions is called facilitated because potassium ions diffuse with the help of integral proteins embedded across the phospholipid bilayer. each of these integral proteins has unique properties that only allow specific substances to move through it. select the true statements. potassium ions cross the cell membrane directly through the phospholipids. facilitated diffusion requires cellular energy. in the video, potassium ions have a net movement into the cell. facilitated diffusion is diffusion assisted by a protein.

Explanation:

Step1: Analyze statement about phospholipids

Potassium ions use facilitated diffusion and don't cross directly through phospholipids, so the first statement is false.

Step2: Analyze energy - requirement of facilitated diffusion

Facilitated diffusion is a passive process and doesn't require cellular energy, so the second statement is false.

Step3: Analyze net movement in video

The illustration and description suggest net movement of potassium ions into the cell, so the third statement is true.

Step4: Analyze definition of facilitated diffusion

Facilitated diffusion indeed is diffusion with the help of integral proteins, so the fourth statement is true.

Answer:

C. In the video, potassium ions have a net movement into the cell.
D. Facilitated diffusion is diffusion assisted by a protein.