Lipids: MCAT

Medistudents Team
May 3, 2023

Lipids form part of the Biological and Biochemical Foundations of Living Systems section of the MCAT syllabus. Although a relatively small topic within the exam, there are some key features which you need to know.  This guide provides a brief overview of the topic and the fundamentals needed for the MCAT exam.

What is the structure of lipids?

Lipids have diverse structures and multiple functions. They are separated into different classes with the most abundant lipids being fats and oils.

For the MCAT exam, you need to be aware of the following:


Steroids can be used to treat a variety of disorders, including asthma and eczema, as well as suppress the immune system following organ transplantation. Steroids are classed as a lipid because they are insoluble in water due to their hydrophobic nature. However, their structure involves 4 carbon rings fused together, known as the cyclopentanophenanthrene ring, unlike the normal lipid structure. Many steroids have additions to this basic structure, for example, cholesterol has a short tail and steroids have the hydroxyl functional group on the A-ring (the first 6-carbon ring).

MCAT: Basic steroid structure.
Figure 1: Basic steroid structure. Blue numbering for each carbon atom. Source:

Terpenes and terpenoids

Terpenes are a type of linear or cyclic hydrocarbons. They are found in small quantities in the body but have essential roles in many bodily functions, including being the precursors of steroids.

Terpenoids are also a group of naturally occurring compounds that are found in all living organisms. Terpenoids and terpenes are used interchangeably, but terpenoids are actually a type of modified terpene that contain additional functional groups. This type of compound is especially important in plant growth and development and is why plants synthesize several hundred terpenoid compounds.

Hopefully this has given you a useful overview of Lipids for the MCAT exam. For more revision materials to boost your MCAT score, visit our MCAT blogs where you’ll find a wide range of MCAT syllabus topics, from the nervous system to the skeletal system, the skin system and many more.