Porin present in ?

Ans. is `d' i.e., Outer membrane of gram negative bacteria Cell envelop of bacteria comprises? An outer membrane (only in gram negative bacteria). A cell wall composed of peptidoglycan. Periplasm (only in gram negative bacteria). Cell membrane (cytoplasmic membrane), which encloses cytoplasm. Outer membranes, which are present only in gram negative bacteria, function as the cell's initial barrier to the environment. The membrane is a bilayered structure composed of lipopolysaccharide. Scattered throughout the lipopolysaccharide macromolecules are protein structures called porins. These control the passage of nutrients and other solutes, including antibiotics, through outer membrane.