A cell can be compared to a hotel where the nucleus is like the hotel manager, controlling activities and storing information. The cytoplasm is similar to the common areas where guests move about and interact. The mitochondria are like the power generators providing energy, and the cell membrane acts as the hotel security, regulating what goes in and out.
cheesy ragu
The mitochondria.
The answers may be found in your textbooks.
If I understand your question correctly, then it would be the mayor.
It could be a gate. It is a gate because the door is the cell membrane. See you need to get past the cell wall before the cell membrane.