What do discs in rods and cones contain?

What do discs in rods and cones contain?

• A. Nucleic acids
• B. Photopigments
• C. Lipids
• D. Proteins

Answer: (B)

Discs in the outer segments of rods and cones are where light detection happens because they are packed with photopigment molecules. These pigments—rhodopsin in rods and photopsins in cones (each bound to retinal)—absorb photons and start the chemical cascade that turns light into an electrical signal for the brain. While the discs are membranes rich in proteins and lipids, their defining feature is the presence of photopigments, which are the actual light-absorbing components that enable vision.

Discs in the outer segments of rods and cones are where light detection happens because they are packed with photopigment molecules. These pigments—rhodopsin in rods and photopsins in cones (each bound to retinal)—absorb photons and start the chemical cascade that turns light into an electrical signal for the brain. While the discs are membranes rich in proteins and lipids, their defining feature is the presence of photopigments, which are the actual light-absorbing components that enable vision.