Lipid Biology Quiz

Phospholipids and Sphingolipids: Structures and Functions

• Phospholipids can form various structures like micelles, bilayers, and vesicles, depending on head group and acyl chain type.
• Glycerophospholipids consist of two fatty acyl chains and a phosphoalcohol esterified to a glycerol backbone.
• The head group alcohol in glycerophospholipids determines their type, and they include phosphatidylcholine and phosphatidylethanolamine.
• Phospholipids like phosphatidylinositol and phosphatidylserine are crucial in signaling cascades and are termed anionic or acidic due to their net negative charge.
• Phosphatidylcholine and phosphatidylethanolamine are the primary components of cell membranes, with varying composition within and between cells and organisms.
• The lipid composition of membranes varies among cell types and organelles, as shown in the composition of three different membranes.
• Sphingolipids, containing similar fatty acids and alcohols as glycerophospholipids, have sphingosine as the backbone alcohol and are involved in apoptosis regulation.
• Sphingomyelin, a major component of the myelin sheath, and ceramide, sphingosine, and sphingosine-1-phosphate are structural examples of sphingophospholipids.
• Sphingolipids have gained attention for their possible involvement in apoptosis regulation and anoikis (programmed cell death).
• Soy lecithin, also known as phosphatidylcholine, is an emulsifier, which is an amphipathic molecule that suspends one type of molecule in another.
• Phosphatidylcholine's structure as an amphipathic molecule allows it to work as an emulsifier, suspending hydrophobic molecules in aqueous solutions.
• Emulsifiers like soy lecithin, or phosphatidylcholine, are crucial in suspending hydrophobic molecules in aqueous solutions.

Fatty Acid Synthesis and Properties Summary

• Fatty acids and ketone bodies share similar synthesis and degradation reactions but have different biochemical pathways and compartmentalization.
• Evolution's outcomes are conserved, and the major enzymes of fatty acid biosynthesis (ACCase and FAS) give insights into the pathway's evolution.
• Different species reveal that genes coding for proteins and enzymes for certain molecules have evolved more recently, addressing needs lacking in simpler species.
• The text provides an overview of main lipid categories: fatty acids, neutral lipids, phospholipids, steroids, bile salts, and eicosanoids.
• Fatty acids are common building blocks of many lipids and are typically unbranched long-chain carboxylic acids with an even number of carbon atoms, often between 12 and 26.
• Fatty acids can be saturated, monounsaturated, or polyunsaturated, with double bonds generally in the cis conformation, and are described using a notation system.
• Fatty acids are characterized by the position of the double bond farthest from the carboxyl group, denoted by ω (omega), and their melting points vary based on length and double bond incorporation.
• The table lists some common fatty acids, their melting points, IUPAC names, and sources, highlighting differences in their properties.
• Fatty acids contain a carboxyl group and act as weak acids, with a pKa of about 4.5, making approximately 99.9% ionized at pH 7.4.
• In the laboratory, fatty acids can be reacted with a strong base to generate a carboxylic acid salt or a carboxylate, increasing their solubility in aqueous solutions.
• The text discusses the structure of oleic acid and major categories of fatty acids, illustrating their long-chain, even-numbered carboxylic acid structure and introducing kinks into the carbon chain with cis double bonds.
• The way fatty acids are synthesized leads to variations in length and double bond incorporation, and their properties are influenced by these structural differences.