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Which one of the following structural formulae of two organic compounds is correctly identified along with its related function?
A
A : Lecithin – a component of cell membrane
B
B : Adenine – a nucleotide that makes up nucleic acids
C
A : Triglyceride – major source of energy
D
B : Uracil – a component of DNA
Detailed Solution
Structure A has a glycerol backbone with two fatty acid chains ($R_1$, $R_2$) joined by ester bonds and a phosphate group linked to choline, $-CH_2-CH_2-N^+(CH_3)_3$. This is the phospholipid lecithin.
Lecithin is a component of the cell membrane, so this identification and function are correct.
A is not a triglyceride, because a triglyceride has three fatty acids and no phosphate group.
Structure B is a purine with two fused rings and an $-NH_2$ group: it is adenine. Adenine is a nitrogenous base, not a nucleotide (a nucleotide also has a sugar and a phosphate).
B is not uracil, which is a single-ring pyrimidine and is found in RNA, not in DNA.
Hence the correct option is A : lecithin – a component of cell membrane.
Lecithin is a component of the cell membrane, so this identification and function are correct.
A is not a triglyceride, because a triglyceride has three fatty acids and no phosphate group.
Structure B is a purine with two fused rings and an $-NH_2$ group: it is adenine. Adenine is a nitrogenous base, not a nucleotide (a nucleotide also has a sugar and a phosphate).
B is not uracil, which is a single-ring pyrimidine and is found in RNA, not in DNA.
Hence the correct option is A : lecithin – a component of cell membrane.