What is the group of oils and fats called?

October 31, 2025 •

3 min read

Biologically, a molecule is defined as a lipid by its insolubility in water, a characteristic shared by fats, oils, and waxes. The group of oils and fats, along with other related compounds like steroids and phospholipids, is collectively known as lipids. This diverse class of organic compounds serves many vital functions for living organisms, from energy storage to acting as structural components of cell membranes.

Quick Summary

Lipids are the scientific term for the family of biomolecules that includes fats and oils. Though fats and oils are specifically referred to as triglycerides, the broader category of lipids also encompasses other compounds with crucial biological functions.

Key Points

Lipids are the scientific group: The overarching scientific term for the class of organic compounds that includes oils and fats is lipids.
Fats and oils are triglycerides: The specific subgroup of lipids that includes fats and oils is called triglycerides, which are formed from a glycerol backbone and three fatty acid chains.
Fats are solid, oils are liquid: A key difference between fats and oils is their state at room temperature, which is determined by the saturation level of their fatty acid chains.
Lipids serve multiple functions: Beyond energy storage, lipids are critical for forming cell membranes, producing hormones, and insulating organs.
Many types of lipids exist: The lipid family is diverse, including not just fats and oils but also waxes, steroids like cholesterol, and phospholipids.
Fat saturation affects health: Saturated fats can increase 'bad' cholesterol, while unsaturated fats (oils) are associated with lower cholesterol levels.

Introduction to Lipids: The Broad Category

While the terms 'oils' and 'fats' are often used casually, they are both specific types of a broader class of organic compounds called lipids. The defining feature of lipids is that they are hydrophobic, meaning they do not dissolve in water. This water-fearing nature is due to their chemical structure, which consists mainly of hydrocarbon chains. The family of lipids is diverse and includes not only dietary fats and oils but also waxes, steroids like cholesterol, and the phospholipids that make up our cell membranes.

The Building Blocks of Fats and Oils

At the chemical level, fats and oils are composed of two main components: a glycerol molecule and three fatty acid chains. This specific structure leads to their more scientific name, triglycerides, or triacylglycerols. It is the nature of the fatty acid chains—specifically, their degree of saturation—that determines whether a triglyceride is a fat or an oil.

Fatty Acids: These are long hydrocarbon chains with a carboxyl group at one end. They are the fundamental building blocks for many types of lipids.
Glycerol: A simple three-carbon alcohol that acts as the backbone to which fatty acids are attached.
Triglycerides: The resulting molecule formed when three fatty acid chains bond to a single glycerol molecule. This is the primary way the body stores energy.

Classifications of Lipids

Lipids are a large and varied group, classified into several categories beyond just fats and oils.

Major Classes of Lipids

Glycerolipids: This class includes triglycerides, which are the main form of energy storage in animals and plants. Fats, which are solid at room temperature, consist of saturated fatty acids, while oils, which are liquid, contain unsaturated fatty acids.
Glycerophospholipids: Essential for creating cellular membranes, these lipids have a phosphate group attached to the glycerol backbone, giving them a hydrophilic 'head' and a hydrophobic 'tail'. This unique structure is crucial for the function of cell membranes.
Sterol Lipids: A key example is cholesterol, a vital component of animal cell membranes and a precursor to other important steroids, such as hormones like estrogen and testosterone.
Waxes: These are long-chain fatty acids esterified to long-chain alcohols and provide protective coatings for plants and animals, such as on leaves or feathers.

The Crucial Biological Roles of Lipids

Lipids play a multitude of vital roles within the body, going far beyond simple energy storage.

Energy Storage: Triglycerides are a highly efficient form of long-term energy storage, providing more than double the energy of carbohydrates per gram. This is critical for metabolic processes and survival during periods of low food availability.
Structural Components: Phospholipids and cholesterol form the core structure of cell membranes, regulating what enters and leaves the cell.
Signaling and Regulation: Steroid hormones, such as estrogen and testosterone, are derived from lipids and act as vital chemical messengers throughout the body.
Insulation and Protection: A layer of fat, or adipose tissue, provides thermal insulation to regulate body temperature and offers a cushioning effect to protect vital organs.
Vitamin Absorption: Fats are necessary for the absorption of fat-soluble vitamins (A, D, E, and K) from the diet into the body.

Comparison of Saturated and Unsaturated Fats


Feature	Saturated Fats	Unsaturated Fats (Oils)
Chemical Structure	No double bonds in the fatty acid chains; saturated with hydrogen atoms.	At least one double bond in the fatty acid chains, causing a bend or 'kink'.
State at Room Temp.	Solid or semi-solid.	Liquid.
Source	Primarily from animal sources (butter, lard) and some plant oils (coconut, palm).	Primarily from plant sources (olive, canola, corn oil) and fish.
Impact on Cholesterol	Can increase LDL ('bad') cholesterol levels.	Can help lower LDL cholesterol levels and raise HDL ('good') cholesterol.
Packaging	Chains pack tightly together, contributing to solid form.	'Kinks' prevent tight packing, leading to a liquid state.

Conclusion

In summary, the correct scientific term for the group of oils and fats is lipids. However, this term represents a far more expansive and crucial family of biomolecules that includes not only triglycerides (fats and oils) but also phospholipids, steroids, and waxes. While fats and oils are primarily known for energy storage, the broader lipid family is essential for everything from cellular structure and hormone production to insulation and vitamin transport. Understanding lipids in this wider context reveals their indispensable role in sustaining all life. For more in-depth biological information, the National Center for Biotechnology Information provides extensive resources.

Frequently Asked Questions

The main difference is their physical state at room temperature. Fats are solid and typically contain saturated fatty acids, while oils are liquid and primarily contain unsaturated fatty acids.

Lipids serve as a high-density energy storage, provide thermal insulation, form the structural components of cell membranes (phospholipids), aid in the absorption of fat-soluble vitamins (A, D, E, K), and act as messengers (steroid hormones).

Yes, cholesterol is a type of lipid known as a sterol. It is a vital component of animal cell membranes and serves as a precursor for important hormones and bile acids.

Lipids, primarily in the form of triglycerides, are stored in specialized fat cells called adipocytes, which make up adipose tissue.

No, while some lipids, like essential fatty acids, must be obtained from the diet, the body's liver and cells can also synthesize many lipids, including cholesterol.

Phospholipids are a major class of lipids that form the structural basis of cell membranes. They have a hydrophilic (water-attracting) phosphate head and two hydrophobic (water-repelling) fatty acid tails.

Lipids are largely nonpolar molecules composed of long hydrocarbon chains. Water is a polar solvent, and because 'like dissolves like,' the nonpolar lipids are insoluble in the polar water.