Final answer:
The cis unsaturated fatty acid that makes up to 80% of olive oil is oleic acid, a monounsaturated fatty acid. It has a bent structure due to its cis configuration, which allows olive oil to remain liquid at room temperature.
Step-by-step explanation:
The cis unsaturated fatty acid that is a major component of olive oil is oleic acid. Olive oil comprises up to 80% of this fatty acid. Oleic acid is a monounsaturated fatty acid (MUFA), which means it contains one carbon-carbon double bond (C=C). This double bond is in the cis configuration, where the hydrogen atoms adjacent to the double bond are on the same side of the chain, creating a bend in the fatty acid's structure. This bent shape prevents triglyceride molecules from packing tightly together, allowing olive oil to remain liquid at room temperature.
In contrast, trans fatty acids have hydrogen atoms on opposite sides of the double bond, which results in a straighter chain that can pack more densely and often results in solid fats at room temperature. Trans fats are associated with health risks, such as increased cardiovascular disease, which is why their uses in foods have decreased. However, it's important to note that the student's question contains a slight error by mentioning cis unsaturated fatty acid as a trans fatty acid, which are two different configurations.