Which of the following lists the three main types of passive transport across cell membranes?

• A. Simple diffusion, active transport, and phagocytosis
• B. Endocytosis, exocytosis, and osmosis
• C. Simple diffusion, facilitated diffusion, and osmosis
• D. Active transport, facilitated diffusion, and pinocytosis

Answer: (C)

Verified step by step guidance

1. Step 1: Begin by understanding the concept of passive transport. Passive transport refers to the movement of substances across cell membranes without the use of energy (ATP). This is driven by the concentration gradient, moving substances from areas of high concentration to areas of low concentration.
2. Step 2: Review the three main types of passive transport: Simple diffusion, facilitated diffusion, and osmosis. Simple diffusion involves the direct movement of molecules through the lipid bilayer without assistance. Facilitated diffusion requires the help of transport proteins to move molecules across the membrane. Osmosis specifically refers to the movement of water molecules through a selectively permeable membrane.
3. Step 3: Compare the options provided in the problem. Eliminate choices that include active transport or processes requiring energy, such as phagocytosis, endocytosis, and exocytosis, as these are not passive transport mechanisms.
4. Step 4: Identify the correct answer based on the definitions of passive transport. The correct answer is the option listing Simple diffusion, facilitated diffusion, and osmosis, as these are the three main types of passive transport.
5. Step 5: Reflect on why the other options are incorrect. Active transport, phagocytosis, pinocytosis, endocytosis, and exocytosis all require energy input and are therefore not considered passive transport mechanisms.