What distinguishes saturated fatty acids from unsaturated fatty acids?

Saturated fatty acids and unsaturated fatty acids are distinguished primarily by their chemical structure, particularly with respect to the presence of double bonds between carbon atoms. Saturated fatty acids have no double bonds; instead, all carbon atoms in the fatty acid chain are fully "saturated" with hydrogen atoms. This saturation leads to a linear structure, allowing them to pack tightly together, which is why saturated fats are typically solid at room temperature.

In contrast, unsaturated fatty acids have one or more double bonds in their carbon chains. The introduction of these double bonds creates kinks in the fatty acid structure, preventing tight packing and resulting in a generally liquid state at room temperature. The presence of double bonds is characteristic of unsaturated fatty acids, which is a defining feature that distinguishes them from saturated fatty acids.

Thus, the correct answer highlights the relationship between the structure of unsaturated fatty acids (the presence of double bonds) and their properties. This fundamental understanding is crucial in fields such as biochemistry and nutrition, as it relates to the physical properties of fats and their roles in biological systems.