Lipids and Membrane Structure

What is the primary function of triacylglycerols in the body?

What is the term for a fatty acid with more than one double bond?

What is the main characteristic that defines a lipid?

What is the name of the fatty acid with a double bond between carbon 9 and 10?

What is the term for a fatty acid that cannot be synthesized by the body?

What is the name of the ester formed from three fatty acids and glycerol?

What is the primary role of bile acids in the body?

What is the term for a fatty acid with no double bonds?

What is the effect of a double bond in fatty acid chains?

What is the function of the phosphate group in phospholipids?

What is the main component of membranes?

What is the function of the fatty acid tails in phospholipids?

What is the name of the lipid that contains sphingosine and a single fatty acyl chain?

What is the name of the lipid raft component that is present in high amounts with cholesterol?

What is the name of the glycolipid that contains ceramide and oligosaccharide chains?

What is the name of the phospholipid head group that contains inositol?

Lipid Structures

Lipids are insoluble in water but soluble in fat and organic solvents
Biological functions of lipids:
- Energy store (triacylglycerols)
- Precursors for vitamins and steroid hormones
- Bile acids
- Membrane structure

Fatty Acids

Definition: Long-chain aliphatic carboxylic acids
Can be:
- Saturated (e.g., myristic acid, palmitic acid, stearic acid)
- Unsaturated (e.g., oleic acid, polyunsaturated fatty acids)
Δ symbol indicates the position of the double bond relative to the carboxylate group
Presence of a double bond introduces a kink into the FA chain, reducing the ability of unsaturated FA to pack together

Triacylglycerols (Triacyclglycerols, TAG)

Ester of three fatty acids and glycerol
Stored in adipose tissue
Function: Energy storage

Phospholipids

Composed of glycerol, two fatty acids, and a phosphate-containing head group
Major component of membranes
Head group and phosphate are hydrophilic, while fatty acids are hydrophobic
Phosphatidyl group consists of phosphate, glycerol, and fatty acid components
Common head groups:
- Choline (Phosphatidylcholine, PC)
- Serine (Phosphatidylserine, PS)
- Ethanolamine (Phosphatidylethanolamine, PE)
- Inositol (Phosphatidylinositol, PI)

Glycolipids

Composed of glycerol, two fatty acids, and a head group containing sugars
Specialized part of membranes
Can have monosaccharide or oligosaccharide chains
Terminal sugar is often sialic acid

Sphingolipids

Lipids that replace glycerol with sphingosine
Sphingosine and a single fatty acyl chain form a unit called ceramide
Ceramide is found in:
- Some phospholipids (e.g., sphingomyelin, SPH)
- Some glycolipids (e.g., GM1 ganglioside)
Ceramide has various oligosaccharide chains attached

Test your understanding of lipid structures, membrane composition, and the fluid mosaic model, including the characteristics of membrane proteins and their orientation.