The passive movement of ions into the occurs through

Options

A. Ion-channels
B. Carrier proteins
C. Diffusion
D. Both (a) and ( c)

Answer

### Step-by-Step Solution:

1. **Understanding Passive Movement**:
- Passive movement refers to the movement of ions or molecules across a cell membrane without the expenditure of energy. This process occurs naturally due to concentration gradients or electrical gradients.

2. **Identifying Ion Channels**:
- Ions can move through specific pathways known as ion channels. These channels are selective for certain ions and allow them to pass through the membrane based on their charge and concentration gradient.

3. **Types of Ion Channels**:
- Ion channels can be classified based on their gating mechanisms (e.g., voltage-gated, ligand-gated). They allow ions to move passively according to their electrochemical gradients.

4. **Role of Carrier Proteins**:
- Carrier proteins facilitate the movement of substances across the membrane. However, they typically require energy (ATP) to function, which classifies them under active transport rather than passive movement.

5. **Understanding Diffusion**:
- Diffusion is a process where molecules move from an area of higher concentration to an area of lower concentration. This process does not require energy and is a key mechanism for passive transport.

6. **Conclusion**:
- The passive movement of ions into the cell occurs through ion channels and by diffusion. Therefore, both ion channels and diffusion are responsible for the passive movement of ions.

### Final Answer:
The passive movement of ions into the cell occurs through ion channels and diffusion.

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