A-LevelBiologyCell membranes and transport9700/12 · May/June 2019 · Q121 Mark
The fatty acids elaidic acid and oleic acid have exactly the same structural formulae, with one double bond in the chain. However, the shapes of the chains are different, as shown in the diagram. [Figure: Diagrams of elaidic acid and oleic acid] Which row shows the effect of the presence of these fatty acids on the structure and behaviour of a cell surface membrane?
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Aelaidic acid: does not fit closely with other fatty acids so that the membrane is less fluid at high temperatures, oleic acid: fits closely with other fatty acids so that the membrane is less fluid at low temperatures
Belaidic acid: does not fit closely with other fatty acids so that the membrane is more fluid at low temperatures, oleic acid: fits closely with other fatty acids so that the membrane is less fluid at low temperatures
Celaidic acid: fits closely with other fatty acids so that the membrane is less fluid at high temperatures, oleic acid: does not fit closely with other fatty acids so that the membrane is more fluid at low temperatures
Delaidic acid: fits closely with other fatty acids so that the membrane is more fluid at low temperatures, oleic acid: does not fit closely with other fatty acids so that the membrane is more fluid at high temperatures
✓ Correct answer
C: elaidic acid: fits closely with other fatty acids so that the membrane is less fluid at high temperatures, oleic acid: does not fit closely with other fatty acids so that the membrane is more fluid at low temperatures
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