Question

Most animal fats form a solid at room temperature, while plant fats remain liquid at room temperature. Which of the following is a feature of lipids in plant membranes that best explains this difference?

1) Plant lipids have shorter fatty acid chains than animal lipids.
2) Plant lipids have more unsaturated fatty acids than animal lipids.
3) Plant lipids have a higher proportion of saturated fatty acids than animal lipids.
4) Plant lipids have a higher melting point than animal lipids.

Answer 1

Plant lipids have more unsaturated fatty acids than animal lipids, which contain a kink in their structure that prevents tight packing and keeps them liquid at room temperature.

Step-by-step explanation:

The Plant lipids have more unsaturated fatty acids than animal lipids. Animal fats are often solid at room temperature due to a higher proportion of saturated fatty acids, which have no double bonds, allowing them to pack tightly together and be solid at room temperature. This includes fats like butter which contains butyric acid, which is a saturated fat. On the other hand, plant oils generally remain liquid at room temperature because they contain a greater proportion of unsaturated fatty acids.

These unsaturated fatty acids have at least one double bond in their structure, which introduces a kink, preventing them from packing tightly together. The presence of these kinks due to the cis double bonds means that the intermolecular forces between the molecules are weaker, leading to lower melting points and causing the oils to remain liquid at room temperature. Examples of these unsaturated fats include olive oil and corn oil. The fluid characteristic of plant lipids is advantageous for the function of cell membranes, particularly in cold environments where saturated fatty acid chains would stiffen and potentially damage the membrane structure.