Transport Mechanisms in Cell Membranes

Cell membranes have hydrophobic cores and charged surfaces, making them effective barriers. While small molecules like water and oxygen can pass through by passive diffusion, larger or charged molecules cannot. Organisms use passive and active transport to move complex molecules across membranes. Passive transport follows an electrochemical gradient without energy, while active transport requires ATP. Transport proteins, such as integral proteins, are essential for some transport processes.

Which type of molecules can freely pass through cell membranes?

• Large proteins

• Charged ions

• Water and simple alcohols

• Complex carbohydrates

What is a characteristic of passive transport?

• Requires ATP

• Occurs along an electrochemical gradient

• Involves only large molecules

• Moves against the electrochemical gradient

Which of the following does NOT require energy expenditure?

• Exocytosis

• Active transport

• Endocytosis

• Passive transport

What is necessary for active transport to occur?

• A concentration gradient

• Energy in the form of ATP

• A hydrophobic environment

• A large surface area

Which type of transport involves the use of transport proteins?

• Neither active nor passive transport

• Only passive transport

• Only active transport

• Both active and some passive transport

What role do transport proteins play in cell membranes?

• They block all molecules from passing

• They facilitate the movement of specific molecules

• They dissolve in the cell membrane

• They only transport water molecules