[Campbell Biology P.122] The text states that 'Nearly every double bond in naturally occurri... | Practice Question

The text states that 'Nearly every double bond in naturally occurring fatty acids is a cis double bond, which creates a kink in the hydrocarbon chain wherever it occurs Figure 5.10b .' Based on this information and the discussion on fat properties, which of the following is the most likely reason why 'hydrogenated vegetable oils' are solid at room temperature, unlike their natural, unhydrogenated counterparts?

  • A: Hydrogenation introduces more cis double bonds, further increasing kinks and making the oil more solid.
  • B: Hydrogenation converts double bonds into single bonds, reducing kinks and allowing molecules to pack more closely.
  • C: Hydrogenation increases the overall molecular weight of the fatty acids, which directly leads to solidification.
  • D: Hydrogenation changes the type of glycerol used, which alters the fat's melting point.

Explanation

Unsaturated fats are liquid at room temperature because their cis double bonds create kinks that prevent the molecules from packing tightly. Hydrogenation is a process that adds hydrogen atoms to double bonds, converting them into single bonds and eliminating these kinks. This allows the fatty acid chains to straighten and pack more closely, leading to a solid or semi-solid state at room temperature.