Which of the following is NOT true regarding cones?

• A. They are responsible for photopic vision
• B. They each contain the same chromophore (11-cis retinal)
• C. They each contain the same protein component (opsin)
• D. Cones are densest in the fovea region

Answer: (C)

Cones drive vision in bright light and enable color discrimination because they have photopigments made of an opsin protein bound to a chromophore. The key point is that there isn’t a single, universal cone opsin. There are three distinct cone opsins—S-opsin for short wavelengths (blue), M-opsin for medium wavelengths (green), and L-opsin for long wavelengths (red)—so each cone type has its own protein component. This is what gives color sensitivity.

All cone types share the same chromophore, 11-cis retinal, which is why photopigment activation in cones follows the same basic chemical process as in rods, but with different opsins providing the spectral tuning. The statement that cones are densest in the fovea is true, since the fovea houses the highest density of cones for high-acuity vision.

So the statement that cones each contain the same protein component (opsin) is not true—the different opsins in the three cone types are what differentiate them and enable color vision.