A characteristic of ion channels is/are

Options

A. They are transmembrane proteins functioning as selective pores
B. They were discovered by Neher and Sakman
C. They are gated channels
D. All of these

Answer

To answer the question "A characteristic of ion channels is/are," we will analyze the characteristics of ion channels based on the provided information.

### Step-by-Step Solution:

1. **Understanding Ion Channels**: Ion channels are specialized proteins embedded in the cell membrane that allow specific ions to pass in and out of the cell. They play a crucial role in various physiological processes.

2. **Transmembrane Proteins**: The first characteristic mentioned is that ion channels are transmembrane proteins functioning as selective pores. This means they span across the cell membrane and create a pathway for ions to move through while selectively allowing certain ions to pass based on size and charge.

3. **Discovery by Neher and Sackman**: The second characteristic is that ion channels were discovered by scientists Neher and Sackman. This highlights the historical significance of their research in understanding ion channels.

4. **Gated Channels**: The third characteristic is that ion channels can be gated. This means they can open or close in response to various stimuli, such as mechanical forces, ligands (molecules that bind to the channel), or changes in voltage across the membrane. This gating mechanism is essential for regulating ion flow.

5. **All of the Above**: The final option states that all of the above characteristics are correct. Since all the previous points are valid, this option is also correct.

### Conclusion:
Based on the analysis, all the options provided in the question about the characteristics of ion channels are correct. Therefore, the correct answer is "All of these are correct."