Lipids-Definition, Structure, Classification, Properties, Example and Function


Another word for ”fat”. A lipid is any of various organic compounds that are soluble only in nonpolar solvents and insoluble in water because water is a polar molecules. Lipids refers to a group of compounds such as oils, steroids, waxes, fats, hormones, fat soluble vitamins, and certain components of membranes and function as energy-storage molecules and chemical messengers. 

Cholesterol and triglycerides are lipids. Lipids are easily stored in the body. The serve as a source of fuel and are an important constituent of the structure of cells. 

Lipid structure: 

A fat molecules consists of two main components-glycerol backbone, fatty acids tails (hydrophobic), and a phosphate group (hydrophilic). As such phospholipids are amphipathic. In the cell membrane, phospholipids are arranged in a bilayer manner, providing cell protection and servings as a barrier to certain molecules. The hydrophilic part faces outward and hydrophobic part faces inward. This arrangement helps monitor which molecules can enter and exit the cell.

Classification (Types) of lipids

Lipids are important fats that serve different roles in the human body. There are numerous types of lipids including- phospholipids, steroid, triglycerides, glycerophospholipid, and sphingolipids.  The main three types of lipids are- simple lipids and complex lipids and derived lipid. 

Simple lipids

A simple lipids is a Easters of fatty acids with various alcohols and carries no other substance. They are soluble in nonpolar solvents such as chloroform and benzene and insoluble in water because water is a polar molecules. 

Fat: Fats in our body are made up of tree molecules joined together this thee molecules structure called a triglyceride. ”Esters of fatty acids with glycerol”. Oils are fats in liquid state.

Waxes: Waxes consist of a long chain fatty acid linked through an ester oxygen to a long chain alcohol. ”Esters of fatty acids with higher molecular weight monohydric alcohols. Waxes re water insoluble due to the weekly polar nature of the ester group.

Complex lipids

Complex lipids are esters of fatty acid containing group in addition to an alcohol and a fatty acid.

Phospholipid: Any of various phosphorous -containing complex lipids such as lecithin and phosphatidylethanolamines.  Phospholipid consist of a hydrophilic (or water loving’) head and a hydrophobic(or’ water fearing) tail. This are lipids containing, in addition to fatty acids and alcohol, phosphate group. Phospholipids are a key component of all cell membranes. They can form bilayers because of their amphiphilic character.  

Glycolipids: Any of a lipids containing a carbohydrate group, commonly glucose or galactose. Their role to maintain the stability of cell membrane.

Derived lipids

When both simple and complex lipids combine and undergo the process of hydrolysis, the produced chemical is know as derived lipids. These including fatty acids, steroids, other alcohols, fatty aldehydes, and ketone bodies hydrocarbons, lipid-soluble vitamins, and hormones.

Fatty acids: Fatty acids are long hydrocarbon chains that are found in certain types of lipids(triglycerides and phospholipids). Fatty acids are the building block of the fat in our bodies and in the food we eat. 

Properties of lipids

  • Lipids may be either liquids or non-crystalline solids at room temperature.
  • Lipids are energy-rich organic molecules, which provide energy for different life processes.
  • No ionic charge.
  • Lighter then water.
  • Insoluble in water.
  • Soluble in organic solvents.
  • Colorless, odorless and tasteless in their pure state.
  • Poor conductor of heat and electricity-efficient insulator for animal body.

 Examples of lipids

Example of common lipid include. All these compounds have similar features, i.e. soluble in organic solvent and insoluble in water.

  • Butter
  • Vegetable oil
  • Cholesterol
  • Cheese
  • Steroids
  • waxes
  • Phospholipids
  • Fat-soluble vitamins(A,D,E,K)

Function of lipids

Lipids have several roles in the body, such as: 

  • Provide nd stores energy.
  • Protect body temperature.
  • Chemical messengers.
  • Formation of membrane lipid layer.
  • activators of enzyme.
  • It provide metabolic fuel.
  • Protection-e.g. protecting plant leaves from drying up.
  • Vitamins A, D, E, K dissolve in fat.
  • Normal growth and development.
  • Separates the cellular components from external environment.


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