Biological membranes only let certain molecules or ions pass, and not at the same speed. This selective permeability is the result of differential passive permeability, which more or less limits the crossing of particles driven by osmotic and electrostatic forces, and biological permeability or permeation, which ensures active transport by enzymatic mechanisms.
Cones provide colour vision while rods cells do not produce colour vision. Rods provide the vision in the dull light (darkness or night), whereas cones are known to give the vision during the day or bright light; Rod cells are more sensitive to light than cone cells and both do have visual pigments with the rod cells possessing rhodopsin and the cone cells having photo-opsins.
