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GOB Chemistry: Lipids and Cell Membranes

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  • What is a lipid?
    A lipid is a naturally occurring molecule from plants or animals that is soluble in nonpolar organic solvents.
  • What are waxes chemically?
    Waxes are carboxylic acid esters of saturated fatty acids and long-chain alcohols, serving mostly external protective functions.
  • What are triacylglycerols?
    Triacylglycerols are carboxylic acid triesters of glycerol, stored in bodies and plants as a major source of biochemical energy.
  • What distinguishes saturated from unsaturated fatty acids?
    Saturated fatty acids have only single C-C bonds, while unsaturated fatty acids contain one or more cis double bonds.
  • Why do vegetable oils remain liquid at room temperature?
    Because they contain a high proportion of unsaturated fatty acids with cis double bonds that create kinks, preventing tight packing.
  • What is saponification?
    Saponification is the hydrolysis of fats and oils by strong aqueous bases to form glycerol and fatty acid salts (soaps).
  • What is a micelle?
    A micelle is a spherical cluster of soap or detergent molecules with hydrophobic ends inside and hydrophilic ends on the surface.
  • What are glycerophospholipids?
    Glycerophospholipids are triesters of glycerol containing charged phosphate diester groups, abundant in cell membranes.
  • What are sphingomyelins?
    Sphingomyelins are amides derived from sphingosine with charged phosphate diester groups, essential in nerve cell membranes.
  • What are glycolipids?
    Glycolipids are sphingosine-derived amides containing polar carbohydrate groups that function as cell surface receptors.
  • What are steroids and their role?
    Steroids are tetracyclic lipids acting as hormones and contributing to cell membrane structure, with cholesterol as a key example.
  • What is the structure of a fatty acid?
    A fatty acid has a carboxylic acid group attached to a long hydrocarbon tail, which can be saturated or unsaturated.
  • What is the difference between fats and oils?
    Fats are triacylglycerols with mostly saturated fatty acids and are solid, while oils have mostly unsaturated fatty acids and are liquid.
  • How does hydrogenation affect vegetable oils?
    Hydrogenation converts unsaturated fats to saturated fats by adding hydrogen to C=C bonds, producing products like margarine.
  • What is the lipid bilayer?
    The lipid bilayer is formed by two layers of phospholipids with hydrophilic heads facing outward and hydrophobic tails inward, forming cell membranes.
  • What is the fluid-mosaic model of cell membranes?
    It describes membranes as fluid (molecules move laterally) and a mosaic of lipids, proteins, and carbohydrates.
  • What is active transport in cell membranes?
    Active transport moves substances across membranes using energy, such as the Na+/K+ pump using ATP to move ions against gradients.
  • What is passive transport?
    Passive transport moves substances across membranes without energy, from higher to lower concentration, including simple and facilitated diffusion.
  • What are eicosanoids?
    Eicosanoids are signaling molecules derived from 20-carbon unsaturated fatty acids, including prostaglandins and leukotrienes.
  • What biological roles do prostaglandins have?
    Prostaglandins regulate blood pressure, platelet aggregation, uterine contractions, gastric secretions, and mediate pain and inflammation.