Detailed Guide on Lipids, Membranes,
and Lipid-Related Diseases
1. What Are Lipids?
Lipids are a broad group of biological molecules that are mostly hydrophobic (water-
repelling) or amphipathic (having both water-attracting and water-repelling parts).
Because water is the main component inside and outside cells, lipids naturally organize
themselves to minimize contact between their hydrophobic parts and water.
This property drives the formation of biological membranes and other lipid structures.
Key Terms:
- Hydrophobic (Nonpolar): Molecules or parts that avoid water, dissolve in organic solvents
like oils or fats.
- Polar (Hydrophilic): Molecules or parts attracted to water and dissolve easily in it.
- Amphipathic: Molecules containing both polar and nonpolar regions.
2. Major Classes of Lipids
Lipids are categorized mainly by their structures and functions:
2.1 Fatty Acids (FAs):
- Long hydrocarbon chains (usually 12-22 carbons) ending with a polar carboxyl group (-
COOH).
, - They serve as building blocks for more complex lipids but rarely exist freely.
- Can be saturated (no double bonds, straight chain) or unsaturated (one or more cis double
bonds causing bends or kinks).
2.2 Glycerolipids:
- Composed of glycerol backbone linked to fatty acids, mainly serve as energy storage (e.g.,
triacylglycerols).
- Store energy densely in adipose tissue.
2.3 Glycerophospholipids:
- Similar to glycerolipids but with a phosphate group attached to the third glycerol carbon,
linked to a polar head group (like choline, serine, ethanolamine).
- Major structural components of cell membranes.
- Their polar heads face aqueous environments, while fatty acid tails form hydrophobic
cores.
2.4 Sphingolipids:
- Based on a sphingosine backbone instead of glycerol.
- Fatty acid attached via an amide bond.
- Involved in membrane structure and cell signaling (e.g., ceramide, sphingosine-1-
phosphate).
- Often carry sugar groups (glycosphingolipids) important for cell recognition.
2.5 Sterol Lipids:
and Lipid-Related Diseases
1. What Are Lipids?
Lipids are a broad group of biological molecules that are mostly hydrophobic (water-
repelling) or amphipathic (having both water-attracting and water-repelling parts).
Because water is the main component inside and outside cells, lipids naturally organize
themselves to minimize contact between their hydrophobic parts and water.
This property drives the formation of biological membranes and other lipid structures.
Key Terms:
- Hydrophobic (Nonpolar): Molecules or parts that avoid water, dissolve in organic solvents
like oils or fats.
- Polar (Hydrophilic): Molecules or parts attracted to water and dissolve easily in it.
- Amphipathic: Molecules containing both polar and nonpolar regions.
2. Major Classes of Lipids
Lipids are categorized mainly by their structures and functions:
2.1 Fatty Acids (FAs):
- Long hydrocarbon chains (usually 12-22 carbons) ending with a polar carboxyl group (-
COOH).
, - They serve as building blocks for more complex lipids but rarely exist freely.
- Can be saturated (no double bonds, straight chain) or unsaturated (one or more cis double
bonds causing bends or kinks).
2.2 Glycerolipids:
- Composed of glycerol backbone linked to fatty acids, mainly serve as energy storage (e.g.,
triacylglycerols).
- Store energy densely in adipose tissue.
2.3 Glycerophospholipids:
- Similar to glycerolipids but with a phosphate group attached to the third glycerol carbon,
linked to a polar head group (like choline, serine, ethanolamine).
- Major structural components of cell membranes.
- Their polar heads face aqueous environments, while fatty acid tails form hydrophobic
cores.
2.4 Sphingolipids:
- Based on a sphingosine backbone instead of glycerol.
- Fatty acid attached via an amide bond.
- Involved in membrane structure and cell signaling (e.g., ceramide, sphingosine-1-
phosphate).
- Often carry sugar groups (glycosphingolipids) important for cell recognition.
2.5 Sterol Lipids:
