Which type of transport of molecules across the plasma membrane requires energy ?

Options

A. Facilitated diffusion
B. Simple diffusion
C. Osmosis
D. Active transport

Answer

To answer the question "Which type of transport of molecules across the plasma membrane requires energy?", we can follow these steps:

### Step 1: Understand the Types of Transport
There are different types of transport mechanisms for molecules across the plasma membrane, including:
- Simple diffusion
- Facilitated diffusion
- Osmosis
- Active transport

### Step 2: Define Each Transport Mechanism
- **Simple Diffusion**: This is the movement of molecules from an area of higher concentration to an area of lower concentration without the use of energy.
- **Facilitated Diffusion**: Similar to simple diffusion, but it involves the use of specific transport proteins to help move molecules across the membrane. It also does not require energy.
- **Osmosis**: This is the diffusion of water molecules through a selectively permeable membrane, moving from an area of lower solute concentration to an area of higher solute concentration, and it does not require energy.
- **Active Transport**: This is the movement of molecules from an area of lower concentration to an area of higher concentration, which requires energy in the form of ATP.

### Step 3: Identify Which Transport Requires Energy
From the definitions:
- Simple diffusion, facilitated diffusion, and osmosis all occur spontaneously and do not require energy.
- Active transport, on the other hand, requires energy to move molecules against their concentration gradient.

### Conclusion
The type of transport that requires energy is **Active Transport**.

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