Number of Membranes in Mitochondria:
Mitochondria have two membranes - the outer membrane and the inner membrane.

Outer Membrane:
The outer membrane of the mitochondria is a smooth, semi-permeable membrane that surrounds the entire organelle. It contains a large number of protein channels called porins that allow the passage of ions, small molecules, and metabolites in and out of the mitochondria.

Inner Membrane:
The inner membrane of the mitochondria is highly folded into structures called cristae, which increase its surface area. This membrane is impermeable to most ions and molecules, allowing for the establishment of a proton gradient that is essential for ATP production through oxidative phosphorylation.

Function of the Two Membranes:
The two membranes of the mitochondria play distinct roles in the organelle's functions. The outer membrane acts as a barrier, regulating the passage of molecules into and out of the mitochondria, while the inner membrane is the site of many critical processes, including the electron transport chain and ATP synthesis.

Conclusion:
In conclusion, mitochondria have two membranes - the outer membrane and the inner membrane, each with specific functions that are essential for the organelle's role in energy production and cellular metabolism.