Monday, August 20, 2012

Monday's Molecule #182

Last week's molecule was a ganglioside (GM2) that's associated with Tay-Sachs disease [Monday's Molecule #181].

This week's molecule is one of the most important enzymes in the known universe. What is it?

Post your answers 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.

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. Please try and beat the regular winners. Most of them live far away and I'll never get to take them to lunch. This makes me sad.

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

UPDATE: The molecule is complex III or ubiquinol:cytochrome c oxidoreductase, the enzyme responsible for the Q-cycle and the transport of proton across the plasma membrane of bacteria and the inner mitochondrial membrane in eukaryotes. This week's winner is Stephen Spiro.

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
July 2: Raul A. Félix de Sousa
July 16: Sean Ridout, William Grecia
July 23: Raul A. Félix de Sousa
July 30: Bill Chaney and Raul A. Félix de Sousa
Aug. 7: Raul A. Félix de Sousa
Aug. 13: Matt McFarlane
Aug. 20: Stephen Spiro


  1. Complex III of the membrane-associated electron transport chain found in mitochondria and in the membranes of bacteria.

    Easy one.

  2. Looks to me like the cytochrome bc1 complex (aka Complex III, or ubiquinol-cytochrome c oxidoreductase).
    Stephen Spiro, UT Dallas

  3. Ooh! Ooh! It's ubiquinol:cytochrome c oxidoreductase, or Complex III for short.

    It oxidises ubiquinol and reduces cytochrome c, using the free energy change to transfer protons to the mitochondrial intermembrane space (or bacterial periplasm), creating a combined electrical and osmotic gradient that can be tapped to generate ATP by allowing the protons to flow back through an ATPase. This mechanism underlies energy-conversion processes in organisms as diverse as chemoautotrophic bacteria and the possessors of plant chloroplasts and our own mitochondria.

    This nicely symmetric enzyme also appears on the cover of some biochemistry book, somewhere.

  4. Cytochrome bc1 complex.

    Also known as Complex III.

    It is an essential part of the electron transport chain for oxicative phosphorylation.

  5. Coenzyme Q - cytochrome c reductase
    also known as "Complex III" of the electron transport chain in mitochondria of nearly all eukaryotes and most eubacteria.
    also known as "cytochrome bc1 complex".

    My real name is Martin Brummell. I am not an undergraduate, I am a PhD student and I live in Saskatoon, Saskatchewan. It's likely I'll visit Toronto some time within the next 2 years (should I win).

  6. Is it a cytochrome-bc1 complex?

    Jim Stewart

  7. and E. coli manages just fine without it

  8. In E. coli, Salmonella and some others, electrons go directly from Complex I to the quinol oxidases via the quinone pool, there is no Complex III and no cytochrome c. I don't have original references to hand but check out Ferguson and Nicholls, Bioenergetics 3, pages 140-143.

  9. That would make a great cover photo for a biochemistry textbook. maybe you could spice up the colour scheme though.