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Questions and Answers
What is the main component of biological membranes?
What is the main component of biological membranes?
What is the parent compound for glycerol-based phospholipids?
What is the parent compound for glycerol-based phospholipids?
What is the characteristic feature of phosphoglycerides?
What is the characteristic feature of phosphoglycerides?
What is the function of gangliosides?
What is the function of gangliosides?
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What is the precursor of steroid hormones?
What is the precursor of steroid hormones?
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What is the characteristic feature of terpenoids?
What is the characteristic feature of terpenoids?
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What is the term for the connection of isoprene units in terpenoids?
What is the term for the connection of isoprene units in terpenoids?
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What is the function of cyclooxygenase (COX)?
What is the function of cyclooxygenase (COX)?
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What is the characteristic feature of steroids?
What is the characteristic feature of steroids?
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What is the biosynthetic pathway of steroids?
What is the biosynthetic pathway of steroids?
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Study Notes
Lipid Structure of Biological Membranes
- Phospholipids are diesters of phosphoric acid, which can form monoesters, diesters, and triesters.
- Phosphatidic acids are the parent compound for glycerol-based phospholipids, consisting of sn-glycerol-3-phosphate with fatty acids esterified at the 1- and 2-positions.
Phosphoglycerides
- Contain a glycerol backbone linked by ester bonds to two fatty acids and phosphoric acid.
- Fatty acid residues have 12-20 carbon atoms.
- The phosphate group at C3 has an ester link to an amino alcohol.
- Comprise the major lipid component of cell membranes.
- Nonpolar tails aggregate in the center of a bilayer, while the ionic head is exposed to the solvent.
Sphingolipids
- The other major group of phospholipids, containing a sphingosine or dihydroxyamine backbone.
- Constituents of plant and animal cell membranes.
- Abundant in brain and nerve tissue, forming a coating around nerve fibers.
Prostaglandins
- Lipid autacoids derived from arachidonic acid, catalyzed by cyclooxygenase (COX).
- C-20 lipids containing a five-membered ring with two long side chains.
- Present in small amounts in all body tissues and fluids, with many physiological effects.
Glycosphingolipids
- Derivatives of ceramide, lacking in phosphorus and nitrogen base.
- Abundant in the myelin sheath of nerves.
- Galactocerebrosides are present in all adult brains, while glucocerebrosides are present in small amounts in certain pathological conditions and in immature brains.
Gangliosides
- Acidic glycosphingolipids with polar heads that are oligosaccharides with one or more residues of sialic acid (N-acetylneuraminic acid or NANA).
- Found in nerve endings and believed to function in the transmission of nerve impulses.
Terpenoids
- Found in plants and account for the flavor and scents of plant structures (flowers and fruits).
- Chemically related to compounds in turpentine (from pine sap) called terpenes, which are hydrocarbons that do not contain esters.
- Derived from isoprene units connected head-to-tail (Isoprene Rule).
Classification of Terpenoids
- According to the number of di-isoprenoid (C10) units they contain.
- Examples include the triterpene lanosterol, the precursor of steroid hormones, and the tetraterpene beta-carotene, a source of vitamin A.
Steroids
- A class of non-saponifiable lipid, defined by structure, with four fused rings A, B, C, and D.
- Carbon atoms are numbered beginning in the A ring, and the six-membered rings are in fixed chair conformations.
- As hormones, steroids are chemical messengers secreted by glands and carried through the bloodstream to target tissues.
- Widely distributed as cholesterol.
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Description
Learn about the structure and composition of phospholipids and phosphatidic acids in biological membranes, including their esterification and importance in natural systems.
