What are lipids?
Besides carbohydrates, proteins and nucleic acids, lipids are one of the four major classes of biologically essential organic molecules found in living organisms.
Lipid molecules contain hydrocarbons and they are what make up living cells’ building blocks of the structure and function. Some common groups of lipids include fats, oils, waxes, certain vitamins, hormones and most of the non-protein membrane of cells.
Lipids are insoluble in water. They are just soluble in nonpolar environments such as choloroform.
People can extract lipids from plants and animals
Types of lipids
Ther are three main types of lipids. They include:
Triglycerides are lipids that can be obtained from food sources of fat (cooking oils, butter or animal fat, for example)
Triglycerides offer an insulation and a layer of padding that helps to maintain body temperature and protect the internal organs from outside impacts, respectively. They also regulate the body’s way of using vitamins.
Whenever the calories consumed are not used up, they are converted to triglycerides and stored for future use. High levels of triglyceride due to regular consumption of food rich in fats can pose health risks.
Steroids includes hormones and cholesterol. The body can both produce cholesterol by itself or obtain it from food. This cholesterol influences the production of hormones which include sex hormones estrogen and testosterone, adrenaline, cortisol and progesterone.
Cholesterol is the most common steroid in the body. It is essential for every living cell since it contributes to cell repair and new cell formation. However, excessive amount of cholesterol is not a good thing when it brings about higher risk of cardiovascular disease.
Phospholipids are derivatives of triglycerides. However, on a molecular level, they are slightly different . For phospholipids, haft of each molecule is water-soluble and the rest is not, making them react differently compared to triglycerides. When located on cell membranes, phospholipids form double-layered membranes: the water-soluble molecules on the outside while the water-insoluble molecules in the inside. Phospholipids provide protection and insulation for cells.
Functions of lipids
Lipids play several roles in the body, including:
- Fueling the body and storing energy
- Sending signals through the body
- Playing as a constituent of cell membranes
Energy storage and provision
Storage lipids are inert triacylglycerols which are made up of three fatty acids and a glycerol.
During fasting, free (unesterified) fatty acids are released from triacylglycerols to provide energy and to form the structural components for cells.
Short and medium chain fatty acids are not esterified but are oxidized in a rapid rate in tissues to give the body “fuel”. Longer chain fatty acids are esterified first to triacylglycerols or structural lipids.
Being small molecules that are insoluble in water makes lipids excellent candidates for signalling. Accordingly, lipids attach to the receptors on the cell surface and bring about a change that leads to an action.
The signalling lipids are in esterified form. They can infiltrate membranes and are transported to bring signals to other cells. Other times, they may bind to certain proteins, remain inactive until reaching the site of action and encountering the appropriate receptor.
Cell membrane constituents
Lipids are the major components of cell membranes. In particular, phospholipids are the principal components that make up basic structure of a cell membrane. Cell menbranes are the boundaries of a cell that protect it from its surrounding. This cell membrane also controls the movement of substances in and out of cells and organelles.
Other roles of lipids in the body
- Maintain body temperature
- Contribute to cholesterol formation
- Contribute to prostaglandin formation and role in inflammation
Hello Health Group does not provide medical advice, diagnosis or treatment.
Review Date: October 23, 2017 | Last Modified: September 11, 2019