Outer mitochondrial membrane resembles the bacterial membrane and the outer chloroplast membrane in having
(a) Selective permeability
(b) Single ion channels
(c) Porins
(d) All of the above

Hint: These are also called beta-barrel proteins present in the outer membrane of mitochondria and the outer chloroplast membrane. They act as a pore through which molecules can diffuse into the cell.

Complete step by step answer:
The outer mitochondrial membrane resembles the bacterial membrane and the outer chloroplast membrane has porins. The outermost membrane of mitochondria is a bilayered phospholipid embedded with integral proteins. This outermost layer of mitochondria contains porins that allow the movement of molecules across them or the membrane. Similar to the outermost membrane of bacteria and outermost chloroplast membrane. This outermost mitochondrial membrane is permeable to water, iron, and proteins so that they can move freely into the inner mitochondrial space. Similarly, it also occurs in the outermost bacterial membrane and also in the outermost chloroplast membrane.
- Selective permeability is the ability of cell membranes to differentiate between different types of molecules and allowing some of them to move in and blocking others to enter inside the cell.
- Single ion channels are pores in the cell membrane that can assume an open state in which iron such as sodium or potassium can pass through.
So, the correct answer is 'Porins'.

Note:
- Porins are present in the outer membrane of mitochondria and the outer chloroplast membrane is also known as beta- barrel protein.
- The outermost membrane of mitochondria is a bilayered phospholipid embedded with integral proteins as in the outer bacterial membrane and also in the outer chloroplast membrane.
- This outermost mitochondrial membrane is permeable to water, iron, and proteins.