Fatty Acids & Triglycerides: Structure, Types, and Energy Storage

Fatty Acid Classification: Saturated, Monounsaturated, and Polyunsaturated

Fatty acids are the main components of triglycerides and phospholipids. They are non-polar and therefore hydrophobic. Their chains consist of covalently bonded carbon atoms with hydrogen atoms.

Saturated fatty acids contain only single bonds, meaning they are "saturated" with hydrogen. Unsaturated fatty acids, conversely, contain one or more double bonds.

Saturated Fatty Acid	Monounsaturated Fatty Acid	Polyunsaturated Fatty Acid

Cis vs. Trans Unsaturated Fatty Acid Isomers

• If hydrogen atoms are on the same side of the double bond, the isomer is cis (e.g., yellow H in diagrams). If hydrogens are on the opposite side of the double bond, the isomer is trans.
• Cis fatty acids have a kink at the double bond, causing them to pack more loosely. This lowers their melting point, making them liquid at room temperature.
• Trans fatty acids do not have this kink, allowing them to pack more tightly. They have a higher melting point and are solid at room temperature.
• Trans fats are partially hydrogenated oils found in some processed foods like margarine. They can pose significant health risks for humans.

Triglyceride Formation: Fatty Acids and Glycerol

• Fatty acids feature a long hydrocarbon chain (composed of carbon and hydrogen) with a carboxyl (acid) group. These chains typically contain 16 to 18 carbon atoms.
• Glycerol contains three carbon atoms and three hydroxyl groups. It reacts with three fatty acids to form a triglyceride (or fat molecule) through a condensation reaction. This process releases three water molecules and forms an ester bond.

Health Risks of Trans Fats and Saturated Fatty Acids

Scientific evidence highlights the health risks associated with excessive consumption of trans fats and saturated fatty acids.

Lipids: Superior Long-Term Energy Storage in Humans

The human body requires energy to function; specifically, each cell relies on an energy source to drive chemical reactions involved in metabolism, growth, and other physiological functions.

Both carbohydrates and lipids (triglycerides) are major energy sources in animals.

• Fats contain approximately twice as much energy as carbohydrates. Each gram of carbohydrates stores about 4 calories of energy, whereas each gram of lipid stores about 9 calories.
• Therefore, lipids serve as a more compact way to store energy, as they contain more energy per gram than carbohydrates. As a result, the body tends to use fat for long-term energy storage and carbohydrates for short-term energy storage.
• Glycogen (carbohydrate storage) can be quickly converted into glucose for energy.
• Triglycerides (fats) contain one glycerol molecule and three fatty acids, and are primarily stored in the body's adipose tissue.
• Fats also provide thermal insulation, protection for organs (acting as shock absorbers), and are precursors for hormones.