University:
University of Phoenix
Course:
BIO 350 | General Biology I
Academic year:

2023
Views:

306

Pages:

2
Author:

kvoterefgk

Unit II Part I (Lipids) Definition: The term lipid was coined by Bloor, who defined lipids as follows: "Lipids are naturally occurring compounds which are soluble in water and soluble in one or more organic solvents such as benzene, chloroform, ether, and acetone, and on hydrolysis yield fatty acids or other alcohols utilized by living organisms." Lipids are thus hydrophobic in nature and are important constituents of plants and animals. In plants, they are present in the seeds, nuts, fruits, protophyll, cell membrane, etc., while in animals, they are stored in adipose tissues, bone marrow, nervous tissue, etc. Lipids are a structurally diverse group of biomolecules, primarily fats, oils, and fatty substances. They comprise a large proportion of carbon, hydrogen, and oxygen and liberate a large amount of energy upon breakdown. Lipids yield water-soluble glycerol and fatty acids upon alkaline hydrolysis. Chemical Composition: Carbon, hydrogen, and oxygen. Classification: On the basis of chemical composition, lipids are classified as follows: A. Simple Lipids: Definition: These are esters of fatty acids with various alcohols. Example: Fats and oils, waxes. B. Compound Lipids: Definition: These are esters of fatty acids with additional groups like phosphate, carbohydrates, etc. Example: Phospholipids, glycolipids. C. Derived Lipids: Definition: These are derived from simple and compound lipids by hydrolysis. This includes fatty acids, alcohol, mono and diglycerides, steroids, terpenes, and carotenoids, etc. Example: Fatty acids, steroids, terpenes. 1. Storage Lipids: Definition: These lipids are mainly meant for storage, e.g., fats, oils, and esters. Example: Fats, oils, waxes. 2. Structural Lipids: Definition: These lipids are responsible for the structure and function of the cell. Example: Phospholipids, glycolipids, cholesterol. Simple Lipids or Storage Lipids: Fats and Oils: Fats and oils are simple lipids or triglycerides (triacylglycerols). Waxes: These are esters of long-chain fatty alcohols and long-chain fatty acids. Compound Lipids or Structural Lipids: Phospholipids: These are the most abundant membrane lipids, containing a phosphoric acid group. Glycolipids: These lipids contain carbohydrates, including monosaccharides. Examples: Phospholipids: Lecithin, plasmalogens. Glycolipids: Blood group substances, cerebrosides. Functional Role of Lipids: Simple Lipids: Serve as energy storage. Compound Lipids: Maintain cell membrane structure and function.