Which of the following is essential for a living cell?

Explanation

This question is asking which of the given options is essential for a living cell. The options are flagella, capsule, cell wall, cytoplasmic membrane, and capsule and cell wall. Flagella are long whip-like structures that some cells use for movement. While flagella are important for some cells, they are not essential for all living cells. Therefore, option A is not the correct answer. A capsule is a protective layer that surrounds some bacterial cells. It helps the cell to avoid being engulfed by white blood cells and to adhere to surfaces. However, not all living cells have a capsule, so option B is also incorrect. The cell wall is a structure that surrounds the cell membrane and provides support and protection to the cell. While the cell wall is important for many cells, not all living cells have a cell wall. Therefore, option C is not the correct answer. The cytoplasmic membrane, also known as the cell membrane, is a thin layer that surrounds the cell and separates the interior from the exterior. It controls the movement of substances in and out of the cell and is essential for all living cells. Therefore, option D is the correct answer. Option E states that both capsule and cell wall are essential for a living cell. However, this is not true as not all cells have a capsule or a cell wall. Therefore, option E is incorrect. In conclusion, the essential structure for a living cell is the cytoplasmic membrane or the cell membrane. This structure is present in all living cells and is responsible for controlling the movement of substances in and out of the cell.