Function of Fats in the Body | Molecule Structure & Composition

Joseph Comunale, Julie Zundel
  • Author
    Joseph Comunale

    Joseph Comunale obtained a Bachelor's in Philosophy from UCF before becoming a high school science teacher for five years. He has taught Earth-Space Science and Integrated Science at a Title 1 School in Florida and has Professional Teacher's Certification for Earth-Space Science.

  • Instructor
    Julie Zundel

    Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

Learn about the function of fats and compare the two types of fats: saturated and unsaturated fats. See the structure of fat and learn how it is formed. Updated: 09/22/2021

Table of Contents


Definition of Fats

Within the studies of biology and nutrition, there are a few large molecules or polymers called macromolecules that perform biological, nutritional, and cellular functions for the organisms that are composed of them. Some macromolecules are the macronutrients that make up the human diet, hence the nutritional phrase of "counting one's macros." Each of these polymers is made up of their own subsequent monomers or smaller molecules bonded together. Fats are a subgroup of the macromolecules or polymers called lipids. Lipids are made up of the monomers fatty acids and glycerol. Lipids and their monomers are composed of the chemical elements carbon, hydrogen, and oxygen. Fats provide many functions for the human body and its cells. Additionally, fats can be broken up into their own categories where different kinds of fats are composed of different kinds of fatty acids.

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  • 0:00 Definition of Fats
  • 0:48 The Structure of Fats
  • 2:26 Saturated and Unsaturated Fats
  • 3:06 The Function of Fat
  • 4:03 Lesson Summary
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Understanding Fat Structure

The macromolecule lipid is structured in varying ways. Fats belong to the subgroup of lipids called triglycerides, tri- meaning "three," and glyceride being derived from "glycerol." Triglyceride or fat structure is composed of three chains of fatty acids bonded to glycerol. Triglyceride molecules vary depending on the kind of fatty acid chains that are bonded to glycerol.

This image shows a ball and stick model of the saturated fatty acid known as palmitic acid. Fatty acids are one of the monomers that are a part of the fat molecule structure.

This image shows one part of the fat molecule structure fatty acid.

The monomer glycerol is another part of fat structure. Notice the three carboxyl groups. This is why the category fats are called triglycerides.

This image shows another part of fat structure. The monomer glycerol.

Fat Molecule Structure

This image shows the basic shorthand structure of a polymer of fat. There are three fatty acid chains bonded to the molecule glycerol.

This image shows what is fat made of.

Looking at the triglyceride molecule, glycerol (left side) is composed of three hydroxyl groups or negatively charged anions composed of one hydrogen and one oxygen atom. Fatty acids (three horizontal chains to the right) vary in their molecular structure. Each type of fatty acid is composed of a carboxylic acid which is made up of a carbon atom double-bonded to an oxygen atom and a hydroxide molecule (oxygen and hydrogen). The carboxylic acid bonds to a long aliphatic chain of carbon atoms bonded with varying amounts of hydrogen at different sides or angles. The aliphatic chains can either be saturated and joined together with single bonds, or unsaturated and joined together with double or triple bonds.

This image shows a ball and stick model of a polymer of fat.

What is fat made of is answered by the name triglyceride. Three fatty acid chains bonded to a glycerol molecule.

Types of Fats

Fats or triglycerides vary in their molecular structure. Fats can either be saturated or unsaturated depending on whether the chains of carbon within fatty acid chains are single bonded or double bonded. Additionally, unsaturated fats can either be polyunsaturated or monounsaturated.


Saturated fats are composed of fatty acid chains that contain single bonds between their carbon atoms, meaning that they are bonded through the sharing of a single pair of electrons. Saturated fats are contained in significant quantities in animal products like whole milk, yogurt, cheese, butter, and ice cream. These kinds of fats tend to be solid at room temperature. Although considered the "bad" fat, saturated fatty acids do perform biological functions for humans such as hormone production and the biochemical process of palmitoylation where the human body uses saturated fatty acids like palmitic acid to stabilize other biological processes. Additionally, they are found to make up parts of cell membranes and provide a padded surrounding for organ tissues.


Unsaturated fats are made up of fatty acid chains that contain double bonds between their carbon atoms, where carbon atoms are bonded through the sharing of two electron pairs. Polyunsaturated fats contain more than one instance of a double bond in their chains, while monounsaturated fats contain only one double bond. Unsaturated fats tend to be liquids at room temperature. These fats are common sources of the dietary essential fatty acids alpha-linolenic acid and linoleic acid which cannot be synthesized within the human body. However, essential fatty acids can be used by the body to synthesize other lipids the body needs. Therefore, unsaturated fats are largely considered the "good" fats. Foods that are high in unsaturated fats are eggs, fish, olive oil, poultry, avocados, and nuts.

Function of Fats in the Body

Fats are one of the macronutrients for the human body. They provide functions in certain biochemical processes and compose important structures within cells. Triglycerides or fats serve the following primary and secondary functions within the human body:

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Frequently Asked Questions

What is the structure and function of fat?

Fat is made up of the monomers glycerol and fatty acid. Fat functions as insulation, padding, and long-term energy storage for organisms. Additionally, fats make up main components of cell membranes, and are responsible for storage of vitamins, filtering toxins, and the synthesis of important hormones.

What does fat consist of?

Fats consist of the monomers or smaller molecules, glycerol and fatty acid. These molecules are composed of the chemical elements hydrogen, carbon, and oxygen.

What is the basic structure of a fatty acid?

The basic structure of a fatty acid is a chain of carbon atoms bonded together that have branching bonds with hydrogen. Fatty acids can consist of carbon atoms bonded in single bonds, as a saturated fatty acid, or double bonds in unsaturated fatty acids.

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