Y1S2 004 II Biochem Lipids Definition, Types, and Functions

Fatty Acids

• Fatty acids with no double bonds are saturated, carrying the maximum possible number of hydrogen atoms (Example: Stearic Acid)
• Fatty acids with at least one double bond are unsaturated, lacking hydrogen atoms (Example: Linoleic Acid)
• Cis fatty acids have hydrogen atoms on the same side of the double bond
• Trans fatty acids have hydrogen atoms on opposite sides of the double bond

Essential/Non-Essential Fatty Acids

• Non-essential fatty acids are produced by the body
• Essential fatty acids are derived from diets and are necessary for vital functions (Examples: Linoleic (C18:2 ω6) and α-Linolenic (C18:3 ω3))

Triglycerides

• Triglycerides are formed from a molecule of glycerol and three fatty acids
• Triglycerides are major components of VLDL and chylomicrons
• Triglycerides are important in metabolism as energy sources and transporters of dietary fat

Phospholipids

• Phospholipids contain one or more fatty acids attached to a phosphate and an alcohol
• Phospholipids may be attached to glycerol or sphingosine
• Phospholipids derived from glycerol are called phosphoglycerides

Lipids

• Lipids are a chemically diverse group of organic compounds, defined by their insolubility in water
• Lipids are highly soluble in non-polar solvents (Chloroform and ether)
• Lipids' water-insolubility contributes to the complexity in their digestion, transport, and metabolism

Types of Lipids

• Fatty acids are long hydrocarbon chains with various lengths and degrees of unsaturation, terminating with carboxylic acid groups
• Fatty acids' carbon atoms are numbered starting at the carboxyl terminus
• The systematic name is derived from the parent hydrocarbon's name, substituting "oic" for the final "e"
• Examples: octadecanoic acid (C18 saturated fatty acid), octadecenoic acid (C18 fatty acid with one double bond), cardiolipin (found in the heart), and sphingomyelin (found in the brain)

Glycolipids

• Glycolipids are sugar-containing lipids derived from sphingosine
• Glycolipids differ from sphingomyelin in the identity of the unit linked to the primary hydroxyl group of the sphingosine backbone
• Examples: cerebroside (simplest glycolipid, found in neural tissue, contains a sugar residue of glucose or galactose)

Sterol Lipids

• Cholesterol is built from 4 linked hydrocarbon rings, with a hydrocarbon tail linked to the steroid at one end and a hydroxyl group attached at the other end
• In membranes, the orientation of cholesterol is parallel to the fatty acid chains of phospholipids, and the hydroxyl group interacts with nearby phospholipid head groups
• Bile salts have the 4 linked hydrocarbon rings plus taurine, glycine, or both (example: originates from cholesterol)

Lipid Profile

• High-density lipoprotein cholesterol (HDL-C): >1.2mmol/l
• Low-density lipoprotein cholesterol (LDL-C): 2.4mmol/l
• Triglyceride

Test your understanding of lipids, including their structures, functions, and importance in biological processes. This quiz covers the definition of lipids, their types, and their roles in the human body, as well as their relationship with certain diseases.