Which part of the cell is responsible for its growth and reproduction?

The nucleus is the part of the cell that is primarily responsible for growth and reproduction. It contains the cell's genetic material (DNA), which directs all cellular activities, including cell division. The nucleus regulates the expression of genes that control processes such as cell growth, replication, and the synthesis of proteins necessary for these functions.

While the cytoplasm and cell membrane perform critical roles in maintaining cell integrity and facilitating various metabolic processes, they do not directly manage the genetic activities required for the growth and reproduction of the cell. The mitochondria are known as the powerhouse of the cell, generating energy through respiration, but they do not handle the cell's growth and reproduction.

Therefore, the nucleus is central to ensuring that a cell can grow by producing the necessary proteins and can reproduce effectively through the processes of mitosis and meiosis, making it the essential component in these fundamental cellular operations.