Cell Structure and Function

Why do polar molecules require carrier proteins to cross the membrane?

• They are too large
• They are charged
• They are toxic
• They cannot pass through the nonpolar lipid bilayer

What is the term for the movement of water across a semipermeable membrane?

• Diffusion
• Active transport
• Facilitated diffusion
• Osmosis

How do neutral solutes typically cross the plasma membrane?

• Facilitated diffusion
• Active transport
• Osmosis
• Simple diffusion

Which process involves the movement of molecules without energy expenditure?

• Active transport
• Phagocytosis
• Exocytosis
• Passive transport

What determines the fluidity of the cell membrane?

• Thickness of the bilayer
• Cholesterol content only
• Protein concentration
• Lateral movement of proteins and lipids