Carotenoids contain

Carotenoids contain

• A. long carbon chains with conjugated double bonds and 6 member rings at each end
• B. straight chains with saturated single bonds only
• C. aromatic rings with alternating double bonds
• D. amino acid residues in a polymer

Answer: (A)

Carotenoids are light-absorbing pigments built from isoprene units, giving a long, nonpolar backbone with many alternating double and single bonds. This conjugated polyene chain lowers the energy gap for electronic transitions, so they absorb in the blue-green region and appear orange to red. Each end of the chain features a six-membered ring, often derived from cyclic end groups like beta-ionone rings. This combination—a long carbon chain with conjugated double bonds and six-member rings at both ends—is exactly what carotenoids are. Straight chains with only single bonds wouldn’t have the necessary conjugation to absorb visible light; aromatic rings imply a different structure with delocalized electrons within benzene-like rings, not this polyene-plus-end-ring arrangement; and amino acid residues in a polymer are unrelated to carotenoids.

Carotenoids are light-absorbing pigments built from isoprene units, giving a long, nonpolar backbone with many alternating double and single bonds. This conjugated polyene chain lowers the energy gap for electronic transitions, so they absorb in the blue-green region and appear orange to red. Each end of the chain features a six-membered ring, often derived from cyclic end groups like beta-ionone rings. This combination—a long carbon chain with conjugated double bonds and six-member rings at both ends—is exactly what carotenoids are. Straight chains with only single bonds wouldn’t have the necessary conjugation to absorb visible light; aromatic rings imply a different structure with delocalized electrons within benzene-like rings, not this polyene-plus-end-ring arrangement; and amino acid residues in a polymer are unrelated to carotenoids.