In membrane transport biology, which of the following processes is a broad category that includes diffusion, osmosis and facilitated diffusion?

Introduction / Context:
Cells must move substances across their membranes to maintain homeostasis. Some movements occur without the cell using metabolic energy, while others require energy input. The overall category for movements that do not require energy is called passive transport. This question asks you to identify which process name includes diffusion, osmosis and facilitated diffusion as subtypes.

Given Data / Assumptions:

• The processes listed include simple diffusion, osmosis and facilitated diffusion.
• We know that these movements occur down a concentration gradient.
• We assume the student can distinguish passive transport from active transport.

Concept / Approach:
Passive transport refers to the movement of substances across cell membranes from areas of higher concentration to areas of lower concentration without the direct use of cellular energy, such as ATP. Simple diffusion, osmosis and facilitated diffusion are all forms of passive transport. In simple diffusion, molecules move directly through the lipid bilayer or through general pores. In osmosis, water moves across a semipermeable membrane. In facilitated diffusion, specific carrier or channel proteins assist the movement of molecules down their concentration gradient. Active transport, by contrast, moves substances against a gradient and requires energy. Therefore, the process that includes all the listed ones is passive transport.

Step-by-Step Solution:
Step 1: Identify that diffusion of a solute, osmosis and facilitated diffusion all involve movement from higher to lower concentration. Step 2: Recall that these movements do not directly require ATP; they rely on the existing concentration gradient. Step 3: Remember that the generic name for energy independent movement down a gradient is passive transport. Step 4: Note that active transport uses ATP or other forms of energy to move substances against a concentration gradient, so it is not in the same category. Step 5: Choose passive transport as the answer because it is the umbrella term that covers diffusion, osmosis and facilitated diffusion.

Verification / Alternative check:
Standard cell biology diagrams often draw two main branches under membrane transport: passive and active. Under passive, they show simple diffusion, osmosis and facilitated diffusion, and under active they show pumps and active carriers that use ATP. This organisation appears in many textbooks and study guides, confirming that passive transport is the process that includes all three specific methods mentioned in the question.

Why Other Options Are Wrong:
Option A, diffusion of a solute across a membrane, refers only to simple diffusion and does not include osmosis or facilitated diffusion as separate named processes. Option C, osmosis, is a specific type of passive transport that involves only water and does not include other solutes. Option D, facilitated diffusion, is another specific subtype of passive transport that uses transport proteins but does not cover simple diffusion or osmosis. Option E, active transport, requires energy input and therefore cannot include passive processes that occur without energy expenditure.

Common Pitfalls:
Students sometimes confuse facilitated diffusion and active transport because both involve membrane proteins. The key difference is that facilitated diffusion is passive and moves substances down a gradient, while active transport is energy dependent and moves substances against a gradient. To avoid mixing them up, always ask whether ATP or another energy source is directly required. If not, the process belongs under passive transport. Remembering this simple test will help you correctly identify passive transport as the umbrella category in questions like this.

Final Answer:
The broad process that includes diffusion, osmosis and facilitated diffusion is Passive transport.