Monday's Molecule #221

Last week's molecule was 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline (OHCU). It is an intermediate in the degradation pathway from uric acid (or urate) to carbon dioxide and ammonia. Uric acid is the main breakdown product in purine catabolism. Humans have lost activity of all of the enzymes of this pathway so they excrete urate. Most other species excrete ammonia, although in other animals some of the terminal enzymes have been lost.

Some textbooks do not show the uric acid degradation pathway since it doesn't occur in humans and those textbooks aren't interested in an evolutionary approach to biochemistry (e.g. Berg, Tymoczko, and Stryer). The other majors textbooks (Voet & Voet, Garrett & Grisham, Nelson & Cox [Lehinger]) all show uric acid converted directly to allantoin via urate oxidase. This reaction was shown to be incorrect about 15 years ago. The actual pathway from uric acid to allantoin involves two intermediates; 5-hydroxyisourate and OHCU.

Image Credit: Moran, L.A., Horton, H.R., Scrimgeour, K.G., and Perry, M.D. (2012) Principles of Biochemistry 5th ed., Pearson Education Inc. page 568 [Pearson: Principles of Biochemistry 5/E] © 2012 Pearson Education Inc.

The winner, for the second week in a row, is Jean-Marc Neuhaus. [Monday's Molecule #220]. Jean-Marc lives in Switzerland so I've made arrangements to fly over there to visit him and treat him to two fondues at the Pinte de Pierre-à-Bot in Neuchatel. Jean-Marc was kind enough to send me a menu [PDF]. There are about 30 different fondues to choose from. If you would like to join us you can leave a comment on last week's post.

This week's molecule is related to a discussion we are having on the How Do the IDiots Explain the Origin of Life? post. Can you identify this molecule? You have to be very specific.

Email your answer to me at: Monday's Molecule #221. I'll hold off posting your answers for at least 24 hours. The first one with the correct answer wins. I will only post the names of people with 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 email message.)

Monday's Molecule #220

Last week's molecule was citrate synthase, one of many enzymes that show considerable amounts of structural change during binding. It looks like the "induced fit" mechanism is a general feature of substrate binding and not something that is limited to just a few examples. That part of the question was easy but the second part was hard. Jean-Marc Neuhaus is this week's winner because he has a copy of my book and was able to look up the explanation. The important point to keep in mind when you are thinking about the thermodynamics of biochemical reactions is that most reactions are near-equilibrium reactions where ΔG = 0. In the case of the citrate synthase reaction, ΔG°′ = -31.5 kJ mol^-1, in the direction of citrate formation. What this means is that the equilibrium concentrations of the products are very much higher than the concentrations of the substrates. These concentrations would be closer to being equal if the reaction was coupled to substrate level phosphorylation (e.g. ATP formation). This would be a problem since the concentration of oxaloacetate (substrate) inside the cell is very low. (Because the standard free energy change of the malate dehydrogenase reaction is ΔG°′ = +30 kJ mol^-1) [Monday's Molecule #219]. Jean-Marc lives in Switzerland so I've made arrangements to fly over there to visit him and treat him to fondue at the Pinte de Pierre-à-Bot in Neuchatel.

Today's molecule is one of those molecules that students should never be asked to memorize. It's an intermediate in a very important pathway. Identify the molecule and the pathway. You have to give me the full name and the common abbreviation. Email your answer to me at: Monday's Molecule #220. I'll hold off posting your answers for at least 24 hours. The first one with the correct answer wins. I will only post the names of people with 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 email message.)

Monday's Molecule #219

Last week's molecule was cobalamin or vitamin B12. The structure was solved by Dorothy Crowfoot Hodgkin who won the Nobel Prize in Chemistry in 1964. There have been ten Nobel Prizes for work on vitamins and coenzymes. There were a lot of people who got this one right. The winner is Piotr Gasiorowski. The undergraduate winner is Jacob Toth [Monday's Molecule #218]. That makes four lunches that I owe Jacob. Right now, he's far away (British Columbia) but he may be coming to Toronto to collect. That may cut down on his chances of winning!

Today's molecule is a very common enzyme found in all species (I don't know of any exceptions). It's part of a pathway that's familiar to all biochemistry students. The figure illustrates a classic "induced fit" mechanism of substrate binding where the binding of one substrate creates the binding pocket for the second substrate. In this case, it's the homodimeric animal version of the enzyme showing rotation of the small domain of one of the subunits. Name the enzyme and the reaction it catalyzes.

There's more. In order to win a free lunch you have to explain something else. It's related to the fundamental concepts that all biochemistry students should know. The standard Gibbs free energy change for the reaction catalyzed by this enzyme is ΔG°′ = -31.5 kJ mol^-1. What does that mean if you are trying to understand the reaction that takes place inside the cell? Is there a reason why this reaction isn't coupled to synthesis of ATP? I'm interested in seeing how most Sandwalk readers understand the fundamental concept of reaction thermodynamics.

Email your answers to me at: Monday's Molecule #219. I'll hold off posting your answers for at least 24 hours. The first one with the correct answer wins. I will only post the names of people with 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 email message.)

Monday's Molecule #218

Last week's molecule was α-tocopherol or vitamin E. You do not need vitamin E supplements and they may even be harmful. Lots of people got it right. The winner was Susan Heaphy [Monday's Molecule #217].

This is the week of Nobel Prize announcements so I've chosen an appropriate molecule. It is very complicated. So complicated, in fact, that there was a Nobel Prize for solving its structure. Name the molecule, the winner of the Nobel Prize, and the year it was awarded. You must get all three answers correct.

Email your answers to me at: Monday's Molecule #218. I'll hold off posting your answers for at least 24 hours. The first one with the correct answer wins. I will only post the names of people with 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 email message.)

Monday's Molecule #217

Last week's molecule was the 5′ cap structure on eukaryotic mRNA. Lot's of people got it right. The winners were Mark Sturtevant and Jacob Toth [Monday's Molecule #216].

As you know, the general public is very gullible. Millions of people have been duped into taking various supplements on the grounds that these supplements will improve their health and/or correct for a deficiency in their diet. These people will freely donate millions of dollars to the quacks who prey on their stupidity. Today's molecule is one of these supplements. Give the common name and the specific name that identifies this particular variant.

Email your answers to me at: Monday's Molecule #217. I'll hold off posting your answers for at least 24 hours. The first one with the correct answer wins. I will only post the names of people with 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 email message.)

Monday's Molecule #216

Last week's molecules were guanine and adenine. Everyone should have known these structures but only undergraduate Zhimeng Yu got it right! [Monday's Molecule #215].

You probably didn't memorize the structure of this week's molecule but you should be able to recognize it and check your answer in a textbook or on the web. What it is it? (I don't know why it has a gray background. Can anyone help? Fixed.)

Email your answers to me at: Monday's Molecule #216. I'll hold off posting your answers for at least 24 hours. The first one with the correct answer wins. I will only post the names of people with 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 email message.)

Monday's Molecule #215

Last week's molecule was malonate (propanedioic acid). A derivative of malonate called malonyl-CoA is a key intermediate in fatty acid synthesis. Bill Chaney was the first person to identify the molecule and describe its function [Monday's Molecule #214].

Recently I've been having a discussion with the Chair of my department about whether undergraduates in introductory biochemistry courses should memorize structures. He thinks they should. I wondered whether all the professors in my department could draw the structures of some important molecules. Here are a couple of molecules that you might be able to recognize. How many of you can identify them without checking a textbook?

How many of you can identify them even with a textbook? I'll need a fairly exact identification. Be sure to specify "top" and "bottom" molecules.

Email your answers to me at: Monday's Molecule #215. I'll hold off posting your answers for 24 hours. The first one with the correct answer wins. I will only post the names of people with 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 email message.)

Monday's Molecule #214

Last week's molecule was 6-phosphogluconate, the second intermediate in the pentose phosphate pathway. Nobody got the right answer! [Monday's Molecule #213].

Classes have now started at most universities in North America so let's celebrate by picking a very simple molecule—one that most undergraduates should recognize if they've taken a biochemistry course. Derivatives of this molecule are essential components of several fundamental pathways; which ones? Give me the common name and the official IUPAC name.

Email your answers to me at: Monday's Molecule #214. I'll hold off posting your answers for 24 hours. The first one with the correct answer wins. I will only post the names of people with 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 email message.)

Monday's Molecule #213

Last week's molecule was 6-phosphogluconolactone, the first intermediate in the pentose phosphate pathway. The winner was Brian Shewchuck [Monday's Molecule #212].

Today (Wednesday, but who's counting?) we're going to continue with basic metabolism in honor of all students who are just being introduced to the wonders of introductory biochemistry. Give the common name and identify the pathway. Explain briefly why this pathway is important.

Email your answers to me at: Monday's Molecule #213. I'll hold off posting your answers for 24 hours. The first one with the correct answer wins. I will only post the names of people with 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 email message.)

Monday's Molecule #212

Last week's molecule was a thymine dimer. The winners were Alex Ling and Matt McFarlane. [Monday's Molecule #211].

Today's molecule is an important part of a major pathway. Give the common name and identify the pathway. Explain briefly why this pathway is important.

Email your answers to me at: Monday's Molecule #212. I'll hold off posting your answers for 24 hours. The first one with the correct answer wins. I will only post the names of people with 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 email message.)

Monday's Molecule #211

Last week's molecule was the the R stereoisomer of ibuprofen [((R)-2-(4-(2-methylpropyl)phenyl)propanoic acid]. The winner was undergraduate Jacob Toth. [Monday's Molecule #210].

Today's molecule is an easy one. All you have to do is give the common name and a brief explanation of its significance.

Email your answers to me at: Monday's Molecule #211. I'll hold off posting your answers for 24 hours. The first one with the correct answer wins. I will only post the names of people with 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 email message.)

Monday's Molecule #210

Last week's molecule was the "go" conformation of the leader sequence in the E. coli trp operon. The winners were Rosie Redfield and Quyen Huynh. [Monday's Molecule #209].

Today's molecule isn't very complicated but it has a big effect. You need to be very specific in identifying the exact molecule shown in the figure. I won't accept answers that are ambiguous.

Email your answers to me at: Monday's Molecule #210. I'll hold off posting your answers 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 email message.)

Monday's Molecule #209

Last week's molecule was depicted on a stamp honoring Gerty Cori. It was supposed to be the "Cori ester" (glucose 1-phosphate) but the image shown on the stamp is not correct. Nobody recognized that so there was no winner last week [Monday's Molecule #208].

Today's molecule is a very famous RNA with secondary structure. Do you recognize it without BLASTing the sequence?

Email your answers to me at: Monday's Molecule #209. I'll hold off posting your answers 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 email message.)

Monday's Molecule #208

Last week's molecule was the fatty acid synthase complex [Monday's Molecule #207]. The winner was Matt McFarlane. He should contact me by email to collect his winnings.

Today's molecule was pictured on a US stamp issued in April 2008. Can you identify the molecule? ... Be precise, there's only one correct answer and it may not be the one you think.

Email your answers to me at: Monday's Molecule #207. I'll hold off posting your answers 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 email message.)

Monday's Molecule #207

Last week's molecule was N-acetylmuramic acid (MurNAc) one of the components of the polysaccharide in bacterial cell walls [Monday's Molecule #206]. The winner was Michael Florea. He should contact me by email to collect his winnings.

Today's (Tuesday's) molecule is a new addition to biochemistry textbooks because its structure was only solved a few years ago. There are plenty of hints in the figure. You have to identify the molecule AND each of the seven activities that are labelled. Bonus points for the PDB identification number and the species.

Email your answers to me at: Monday's Molecule #207. I'll hold off posting your answers 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 email message.)

Better Biochemistry

This is a "Theme" post where I collect all previous posts on teaching biochemistry and molecular biology.

March 22, 2015
On the handedness of DNA

March 5, 2015
Don't misuse the word "homology"

January 28, 2015
Vision and Change

January 28, 2015
Evidence-based teaching

January 15, 2015
The Nature of Science (NOS)

January 11, 2015
Why can't we teach properly?

January 8, 2015
Evolutionary biochemistry and the importance of random genetic drift

January 3, 2015
Thinking critically about the Central Dogma of Molecular Biology

December 9, 2014
On the meaning of pH optima for enzyme activity

December 9, 2014
On the specificity of enzymes

December 4, 2014
How to revolutionize education

October 20, 2014
How not to teach biochemistry

October 3, 2014
Metabolism first and the origin of life

September 11, 2014
The mystery of Maud Menten

August 8, 2014
Historical contingency and the evolution of the glucocorticoid receptor

July 28, 2014
Finding the "perfect" enzyme

Jun 2, 2014
"Flipping the classroom": what does that mean?

April 25, 2014
ASBMB Core Concepts in Biochemistry and Molecular Biology: Molecular Structure and Function

April 24, 2014
ASBMB Core Concepts in Biochemistry and Molecular Biology: Biological Information

March 21, 2014
ASBMB Core Concepts in Biochemistry and Molecular Biology: Homeostasis

March 5, 2014
The crystal structure of E. coli RNA polymearse σ70 holoenzyme

January 10, 2014
How not to teach biochemistry at memorize.com

December 9, 2013
Monday's Molecule #226

December 6, 2013
Die, selfish gene, die!

December 6, 2013
Do you understand this Nature paper on transcription factor binding in different mouse strains?

December 2, 2013
Monday's Molecule #225

November 12, 2013
David Evans Says, "Teach What the Vast Majority of Scientists Affirm as Settled Science"

November 5, 2013
Stop Using the Term "Noncoding DNA:" It Doesn't Mean What You Think It Means

October 30, 2013
Time to Re-Write the Textbooks! Nature Publishes a New Version of the Citric Acid Cycle

October 29, 2013
The Khan Academy and AAMC Teach Evolution in Preparation for the MCAT

October 29, 2013
The Khan Academy and AAMC Teach the Central Dogma of Molecular Biology in Preparation for the MCAT

October 29, 2013
The Khan Academy and the Association of American Medical Colleges (AAMC) Team Up to Teach Evolution and Biochemistry for the New MCAT

October 24, 2013
ASBMB Core Concepts in Biochemistry and Molecular Biology: Matter and Energy Transformation

October 15, 2013
ASBMB Core Concepts in Biochemistry and Molecular Biology: Evolution

October 14, 2013
Fundamental Concepts in Biochemistry and Molecular Biology

October 11, 2013
ASBMB Promotes Concept Driven Teaching Strategies in Biochemistry and Molecular Biology

Another curious aspect of the theory of evolution is that everybody thinks he understands it. I mean philosophers, social scientists, and so on. While in fact very few people understand it, actually, as it stands, even as it stood when Darwin expressed it, and even less as we now may be able to understand it in biology. Jacques Monod (1974)October 8, 2013
On the Importance of Defining Evolution

October 6, 2013
Teaching Biochemistry from an Intelligent Design Creationist Perspective

October 1, 2013
The Many Definitions of Evolution

September 30. 2013
The Problems With The Selfish Gene

September 18, 2013
Breaking News!!! Wikipedia Is Wrong! (about the Central Dogma)

September 13, 2013
Sean Carroll: 'What Is Science?"

September 13, 2013
Better Biochemistry: Teaching ATP Hydrolysis for the MCAT

September 12, 2013
Better Biochemistry: Teaching to the MCAT?

June 27, 2013
The Best Enzyme

April 16, 2013
Where Do Organisms Get Their Energy?

April 10, 2013
Spontaneous Degradation of DNA

March 18, 2013
Estimating the Human Mutation Rate: Biochemical Method

Monday's Molecule #206

Last week's molecule was myricyl palmitate, the major component of beeswax [Monday's Molecule #205]. The winner was Bill Chaney. There was no undergraduate winner.

Today's molecule is a very common molecule shown in a somewhat unusual conformation. (It's the conformation of the molecule when it's bound to a certain enzyme.) Identify the molecule (common name only). Can you describe the conformation?

Email your answers to me at: Monday's Molecule #206. I'll hold off posting your answers 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 email message.)

Monday's Molecule #205

Last week's molecule was the lipoamide swinging arm of pyruvate dehydrogenase [Monday's Molecule #204]. The winners were Alex Ling and Michael Florea.

Today's molecule is a major component of something you are all familiar with. Identify the molecule (common name only) and where it's most likely to be found. (Hint: not in humans.)

Email your answers to me at: Monday's Molecule #205. I'll hold off posting your answers 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 email message.)

Monday's Molecule #204

The last Monday's Molecule was α-linolenate [Monday's Molecule #203]. It is an omega-3 essential fatty acid. The winner was Anders Ehrnberg.

Today's molecule is actually three different molecules (1,2 and 3). Give the common names for the terminal part of each molecule—the names used in most textbooks. Identify E₂ (enzyme name) and briefly explain what's going on.

Email your answers to me at: Monday's Molecule #204. I'll hold off posting your answers 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 email message.)

Monday's Molecule #203

The last Monday's Molecule was medium chain acyl-CoA dehydrogenase (MCAD) (PDB 2AIT). Nobody got the right answer [Monday's Molecule #202].

Today's molecule is very important for humans. You need to supply the common name AND a more official IUPAC name that identifies the configuration of the bonds. You also need to briefly explain why this molecule is important in humans.

Email your answers to me at: Monday's Molecule #202. I'll hold off posting your answers 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 email message.)