The correct option is (a).
Explanation
Mitochondria are double-membrane-bound organelles present in eukaryotic cells. They are structurally distinct due to their envelope system, which divides the organelle into two aqueous compartments: the intermembrane space and the matrix.
Statement-wise Analysis
- Statement 1 is Correct: Mitochondria possess a double membrane envelope consisting of an outer membrane and an inner membrane. This distinguishes them from single-membrane organelles like lysosomes or vacuoles.
- Statement 2 is Incorrect: The inner membrane is not smooth; it is deeply folded inwards to form structures called cristae. These folds significantly increase the surface area available for the chemical reactions involved in ATP generation.
- Statement 3 is Incorrect: The outer membrane is porous and permeable to monomers of carbohydrates, fats, and proteins. It contains transport proteins known as porins. It is the inner membrane that is semi-permeable and highly selective.
Key Takeaway: Mitochondria are characterized by a porous outer membrane and a deeply folded inner membrane (cristae), which maximizes the surface area required for cellular respiration and energy production.