Lipids are a diverse group of mostly nonpolar molecules that do not dissolve readily in water. This lesson introduces the structure and functions of fats, oils, and waxes, with a focus on how fatty-acid structure affects the properties of fats.
Many lipids consist largely of hydrocarbon regions with nonpolar carbon–carbon and carbon–hydrogen bonds. Because water is polar, these nonpolar molecules are generally hydrophobic, meaning they do not mix readily with water.
All flashcards
What makes a molecule hydrophobic?
A hydrophobic molecule does not mix or dissolve readily in water. Many lipids are hydrophobic because they contain extensive nonpolar hydrocarbon regions.
How is a triglyceride assembled?
Three fatty acids attach to the three-carbon glycerol backbone through ester bonds. Formation of the three bonds releases three water molecules.
How do saturated and unsaturated fatty acids differ?
Saturated fatty acids have only single bonds between carbon atoms. Unsaturated fatty acids have one or more carbon–carbon double bonds.
How does a cis double bond affect a fatty-acid chain?
It creates a bend or kink in the chain, making it harder for fatty-acid chains to pack tightly.
What are essential fatty acids?
They are fatty acids the human body needs but cannot synthesize, so they must be obtained from food. Omega-3 and omega-6 fatty acids are essential.
Quiz questions
Why are many lipids hydrophobic?Answer: Their nonpolar hydrocarbon regions interact poorly with polar water.
Which components form a typical triglyceride?Answer: One glycerol molecule and three fatty acids.
Why are fats rich in saturated fatty acids often solid at room temperature?Answer: Their straight chains can pack closely together.
Why do cis-unsaturated oils often remain liquid at room temperature?Answer: Cis double bonds bend fatty-acid chains and hinder close packing.
What health concern is associated with consuming trans fats?Answer: They may raise LDL levels, contributing to arterial plaque and heart disease risk.
Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.