B

Figure 22.2: Structural details of nucleus. (A) whole and (B) enlarged view of nuclear pore.

Nuclear pore is 100nm is diameter and consists of several proteins. It is a gateway for transfer of material between nucleus and cytosol. RNA formed after transcription from DNA within the nucleus and move out of the nucleus into the cytosol through nuclear pore. Similarly protein from cytosol crosses nuclear pore to initiate replication, transcription and other processes.

1. Mitochondria- It is popularly known as “power house of the cell” as the organelle is actively involved in the generation of ATP to run the cellular activities. Mitochondria is a double layered membrane bound  organelle with different structural properties (Figure 22.3, A). Outer membrane is smooth and cover the complete organelle with large number of integral protein, known as porin.