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Monday, June 25, 2012

Monday's Molecule #175

If you look closely, you'll see that today's molecule is an unusual variant of a very common cell component. Your task for today is NOT to give this molecule a specific name but rather to describe it in general terms and identify three (3) ways in which it differs from the more common molecules. Finally, you have to tell us where these molecules are found.

Post your answer as a comment. I'll hold off releasing any comments for 24 hours. The first one with the correct answer wins. I will only post mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch with a very famous person, or me.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your comment.)

Some past winners are from distant lands so their chances of taking up my offer of a free lunch are slim. (That's why I can afford to do this!)

In order to win you must post your correct name. Anonymous and pseudoanonymous commenters can't win the free lunch.

Winners will have to contact me by email to arrange a lunch date.

Comments are invisible for 24 hours. Comments are now open.

UPDATE: This is a typical bacterial membrane lipid found in archaebacteria (Archaea) and in some gram-negative bacteria. It differs from the glycerophospholipids in eukaryotes and other bacteria in three ways. (1) The backbone molecule (a three carbon glycerol molecule) is sn-glycerol-1-phosphate, a stereoisomer of the more common backbone sn-glycerol-3-phosphate, found in other lipids. (2) The long fatty acid chains are attached to the glycerol moiety by an ether linkage, rather than an ester linkage. (3) The hydrocarbon chains of the fatty acid chains are composed of isoprenoid units methyl units. Today's winner is Raul A. Félix de Sousa (again).

Nov. 2009: Jason Oakley, Alex Ling
Oct. 17: Bill Chaney, Roger Fan
Oct. 24: DK
Oct. 31: Joseph C. Somody
Nov. 7: Jason Oakley
Nov. 15: Thomas Ferraro, Vipulan Vigneswaran
Nov. 21: Vipulan Vigneswaran (honorary mention to Raul A. Félix de Sousa)
Nov. 28: Philip Rodger
Dec. 5: 凌嘉誠 (Alex Ling)
Dec. 12: Bill Chaney
Dec. 19: Joseph C. Somody
Jan. 9: Dima Klenchin
Jan. 23: David Schuller
Jan. 30: Peter Monaghan
Feb. 7: Thomas Ferraro, Charles Motraghi
Feb. 13: Joseph C. Somody
March 5: Albi Celaj
March 12: Bill Chaney, Raul A. Félix de Sousa
March 19: no winner
March 26: John Runnels, Raul A. Félix de Sousa
April 2: Sean Ridout
April 9: no winner
April 16: Raul A. Félix de Sousa
April 23: Dima Klenchin, Deena Allan
April 30: Sean Ridout
May 7: Matt McFarlane
May 14: no winner
May 21: no winner
May 29: Mike Hamilton, Dmitri Tchigvintsev
June 4: Bill Chaney, Matt McFarlane
June 18: Raul A. Félix de Sousa
June 25: Raul A. Félix de Sousa


  1. Raul A. Félix de SousaMonday, June 25, 2012 11:02:00 AM

    Molecule #175 is a generic image representing the phospholipids that constitute the membranes of organisms of the domain Archaea. They differ from the membrane phospholipids of other organisms because: 1) The stereochemistry of the glycerol unit is reversed (Archaea use L-Glycerol), 2) Instead of fatty acids Archaea use isoprene-derived branched long chains 3) these chains are not carboxylic acids, but alcohols and therefore glycerol is bound to them as ethers, not esters.

  2. It is a membrane lipid of archaea. It differs from classical phospholipids from bacteria or eucaryotes by:
    - having prenyl (geranylgeranyl) chains instead of acyl chains
    - having ether bonds instead of ester bonds
    having the phosphate in position 1 instead of 3

  3. I've seen reviews asserting that the stereochemical difference is the most basic, and that there are exceptions to distinctions involving the isoprenyl chains and ether linkages. Is that accurate?