A Levels Biology (9700)•9700/13/M/J/23

Explanation
Comparing carbon chain lengths in triglycerides Steps:
- Recall fatty acid carbons: palmitic (P) = 16C, oleic (O) = 18C, stearic (S) = 18C.
- Compute total carbons for SOS: S + O + S = 18 + 18 + 18 = 54C.
- Compute total carbons for POP: P + O + P = 16 + 18 + 16 = 50C.
- Subtract: 54 - 50 = 4 more carbons in SOS than POP.
Why C is correct:
- Total fatty acid carbons define chain length; SOS uses three 18C acids (54C) vs. POP's two 16C and one 18C (50C), yielding a 4C difference.
Why the others are wrong:
- A: POS has one unsaturated acid (O), not two.
- B: POS totals 52C (P + O + S), more than POP's 50C.
- D: Acids join glycerol via ester bonds, not hydrolysis (which cleaves them).
Final answer: C
Topic: Carbohydrates and lipids
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