Category: Food Science

Did you ever notice that good chemists are very often also good cooks?…

Grossly Oversimplified Science: Obtaining Pure Yeast Cultures

Various yeasts of the genus Saccharomyces (particularly the “Baker’s Yeast” Saccharomyces cerevisiae) represent quite possibly the most important bit of intentional microbiology that we have. We eat and drink the little critters and their byproducts in more or less every human culture that I know of, and are now getting more seriously into burning them, too.

As I’ve mentioned before, gluttony is my second most favorite deadly sin, so bread and booze microbiology is naturally of interest to me. It seemed worthwhile to look into developing my own yeast (and bacteria…but that’s for another post) stocks to brew, vint, and bake with, so I did some poking around. I dug out my copy of Rog Leistad’s “Yeast Culturing for the Homebrewer”, Peter Duncan and Bryan Acton’s “Progressive Winemaking”, a number of internet sources, and finally some scientific papers. I know, I’m a nerd.

I have so far not found much of anything about isolating yeasts from scratch – virtually everything seems to assume that you will “buy” your yeast from somewhere else, and aside from scientific papers most assume that you’re only bothering to culture your own yeast to save money by stretching the sample you bought to brew several batches before buying more yeast from “the professionals” again. This annoys me.

Unfortunately, I’m still on the road and haven’t had time to directly embark on my culture project here. I’m also having a heck of a time tonight trying to come up with a way to make the process of isolating a pure culture sound interesting to anyone besides me. Here’s the extremely abbreviated version:

  • Take something that’s got (in this case) yeast in it (sourdough starter, unfiltered beer, whatever)
  • Make up some solidified yeast food: typically this is something like a mixture of sugar, predigested milk protein, and water, mixed with agar to solidify it, and with a small amount of acid added, since the acidity helps inhibit bacteria that might contaminate the yeast culture
  • Take a tiny bit of the original stuff-with-yeast-in-it, and smear it thinly over the top of the solid medium.
  • Cover the solid medium and put it somewhere warm for a while until you can see individual spots (“colonies”) of growth

    • (The idea is that if done right, at some point on the solid media the “smearing” will have spread out the yeast cells far enough that you can make out the mounds of offspring that an individual yeast cell has made. Each distinguishable round spot of growth is effectively made up of millions of clones of the original single cell that started the “colony”)

  • Take a bit of a single colony and put it in some sterile culture media.

If everything works correctly, this gives you a “pure” culture, isolated from any other kinds of cells that may have been in the original sample. In this example, this is hopefully a brewing or bread yeast culture that you can now use to make beer, wine, bread, or fuel ethanol (the latter assuming you have permission from the Bureau of Alcohol, Tobacco, and Firearms, since it requires distillation.)

Tomorrow: Fun facts about yeast cultures.

All this week: A topic important to secular and religious people alike

It’s not midnight here yet, I’m still on time!

Hello, “Just Science 2008” subscribers and everyone else. My life is insane at the moment but dagnabbit I’m going to do my best to get at least one post up on a scientific topic every day from today (Monday, February 4th) until Friday…

Today’s post is in the form of a gedanken experiment.

First, imagine the following:

  • Some “entities” existing somewhere

    • It doesn’t matter what “entities” you are imagining, whether they are products in a market setting, or data structures in a computer program, or topics of discussion on a news broadcast. All that matters is that there can be more than one of them.

  • A mechanism by which these “entities” are copied (and, optionally, also sometimes removed)

    • Products are manufactured or recalled, data structures can be copied or deleted, additional news anchors can be added to comment on a topic or conversely may shut up about them…

  • At least one mechanism by which changes can occur between or during copies

    • Product designs can be changed, a computer program may consult a “random number” generator and use it to make small changes in the data structure, scriptwriters may alter the news anchor’s teleprompter messages…

  • Some aspect of the “entities” that affects the rate at which they are copied (and/or, optionally, removed).

    • Demand by buyers in the market results in ramping-up of production, a computer program may perform some test or comparison of a data structure and use the result to determine how many copies of it to make (or whether or not to delete it), news topics that result in more people watching are repeated more often while those that people tune out from are dropped from the schedule…

What happens to this group of “entities” over time should be obvious. Taking the example of products in a market, producers introduce a variety of products (the group of “entities” in this example) and buyers examine their characteristics and, based on which ones they like, buy some of them. The producers observe which kinds of products are selling more and make more of those, while reducing or outright eliminating the production of those that aren’t selling well. Over time, a few of the kinds of products in this group which best fit the preferences of the buyers and the ability of the producers to make them. These products will dominate the market until the preferences of the buyers or the ability of the producers to produce them change [example: a shortage in the price of a particular material needed for a popular product].

You have most likely observed this process in the “news topic” context yourself, where it tends to happen much faster as “cheap and easy” news stories are happily picked up by news agencies to broadcast until people get sick of them and tune out.

This can all, hopefully, be understood as a purely logical outcome – a conclusion that universally and necessarily follows from the premises given. There should be nothing supernatural or even surprising here, is there?

So, now that you understand why and how evolution works (if you didn’t before), I can move on. (Incidentally, the part of the example above that describes a computerized system is actually referred to as a “genetic algorithm”.)

My purpose in starting with this is because it really and truly is fundamental to the topic that I expect to spend most of this week posting about, and which has been of vital importance to human culture and intellectual development for thousands of years. This most important subject involves such notable figures as Charles Darwin,St. Thomas Aquinas, Noted American Science-guy Benjamin Franklin, New England Puritan Cotton Mather and Quaker William Penn ,Hardcore Catholics like Pope John Paul II, Hardcore Athiests like PZ Myers, even famous religious figures like Jesus.

I refer, of course, to wine (and beer and other examples of ethanol production).

Okay, here’s the background: I just graduated with my B.S. in Microbiology, and I’ve got this whole “Hillbilly Biotech”/”Do-it-yourself”/”Practical Science” kind of thing going on in my interests. That being the case, I wondered what it would take to isolate, culture, and maintain my own yeast (and bacteria – more on that later) stocks from the environment rather than buying “canned” cultures – or at least play with the “canned” yeasts to create my own stocks. As I was poking around, though, I kept running into the same attitudes – namely that it’s “too hard” to do this, and although there are a number of people who advocate re-culturing canned commercial yeasts for a short time to save money, none of them think it’s feasible to do this for more than a couple of generations, at which point we are assured that you have to go buy it again or else “mutations” will inevitably appear and scary and mysterious “off-flavors” will result and the brewing police will come and throw you in jail for deviating from the archetype of whatever pre-defined style of wine or beer you’re trying to make. Or something like that. In any case, it’s because of this fear of “mutations” that I am starting out with this “evolution”-related post: in biological evolution, various forms of alterations in the genetic material are the “changes before or during copying” in the gedanken experiment above.

I didn’t buy it when people were telling me that it was “too hard” to learn how my computer works so that I could run Linux and should instead leave deciding what my computer should do to the “professionals”, and I’m not buying the same argument about commercial yeasts, either. If I felt that way, I might as well leave the rest of the complex technology of brewing to the “professionals” too, and consign myself to “Lite Beer” and “Thunderbird” for the rest of my life.

I’ve been spending much of the last few weeks perusing books, online articles, and scientific papers on subjects related to brewing in general and brewing yeasts in particular, and this should form the bulk of this week’s post topics, of not well beyond this week. Tomorrow I intend to start in on the actual process of culturing yeasts. Meanwhile, feel free to correct my no doubt horribly over-simplified explanation of evolutionary processes in the comments.

I should be getting more done…

Im Name des Nudelmonster! It’s been over a week since my last post!

“Someone” seems to have located a replacement original disk of a game I had many years ago (but lost when I loaned it to someone) and bought it for me. Now, in addition to a variety of issues I need to deal with related to moving over the next few months, I have this delightfully surreal old computer game beckoning at me. ARGH! MAKE IT STOP!

Meanwhile, I’ve been trying to put together topics for next week’s “Just Science 2008”. We’ll find out who, besides me, is interested in fermentation once it starts. I think I’ll have to start off the series with a post on evolution, however, since it really does play a fundamental role when it comes to yeast culture. I also think I may be able to work JellO® into at least one of the posts, too…

Internet connection will be spotty the rest of this week as we travel towards the area that is to be our New Home, but I should have posts assembled in time for next week.

If I get a chance, there will hopefully be at least one more Geostrings post, possibly with a sample mp3 and/or Ogg/Vorbis audio file.

’tis the season to be greedy

Members of my immediate family start asking around this time of year about what kinds of things I’d like for Christmas presents this year.

This strikes me as a good way to break the week-long bout of blogstipation I’ve been having. Here, then, is what I want for Christmas, Xmas, Hannukah, Kwanzaa, Cephalopodmas, or whatever gift-giving winter holiday you prefer (each category is sorted roughly in order of desire at the moment):

Ridiculously Expensive Stuff

Which I only list on the off-chance that someone wins the lottery or happens to find an amazing bargain on “e-bay®” or something.

Relatively Expensive Books

Other kinda-expensive-but-maybe-you-can-find-it-at-reasonable-price stuff

Relatively Cheap Stuff (but still spiffy)

I know there was more, but my brain seems to have gone on break right now…

“Does beer and ice cream make gas?”

I get some odd Google searches hitting this site. Once in a while, however, I see one asking a question of vital importance and great usefulness to the general public. Today’s brief topic is this query: “Does beer and ice cream make gas?”.

I’m assuming the searcher did not mean gasoline. Biodiesel is all well and good, but who the heck would waste perfectly good beer and ice cream on such a thing? No, I assume the searcher wanted to know if eating these two fine foods together would expose one to the risk of increased flatulence.

Sad to say, the answer is most likely “yes”.

Flatulence gas (from humans, at least) is made up mostly of carbon dioxide and hydrogen gas[1], and for some people (but apparently not all!) methane. It’s worth noting that none of these components have any odor. All of the offensive smell comes from comparatively tiny amounts of sulfur-containing chemicals – most notably plain old Hydrogen Sulfide, and maybe a few molecules of indole-type compounds such as skatole which can make the origin of the stench obvious.

These main gases come from two sources – swallowed gases (air and carbonated beverages) and microbial fermentation. Obviously this is one place beer comes in – the carbonation adds to the amount of gas entering the digestive tract. Secondly, the beer probably contains some amount of remaining malt which some intestinal bacteria, like the yeast that made the beer in the first place, can break down and eat, possibly generating more carbon dioxide in the process. Beer also has small amounts of sulfur compounds in it which give it some of its flavors. It’s possible that some of this sulfur can end up as smelly by-products of microbial action as well.

I tend to assume that problems one might have with ice cream are mainly related to the lactose from the cream. Lactose is actually a combination of two kinds of “simple” sugar molecules linked together in pairs – glucose and galactose. Many unfortunate human beings are cursed with a lack of production of lactase, which is an enzyme that breaks lactose into its two simple sugars which can be easily absorbed and digested. Many bacteria which can live in the human intestine, on the other hand, make their own lactase. If the human eating the ice cream doesn’t make their own lactase so as to absorb and use up the simple sugars, it all gets down to the intestines where the intestinal bacteria can turn it into a major feast. Many bacteria generate a lot of carbon dioxide when eating these sugars, too, and this adds to the gases that build up in the intestine. This is similar to the issue with beans[2] and similarly ‘indigestible’ substances which can appear in food[3] – humans don’t use them up, so the bacteria get it all and make a huge amount of gas in the process of eating it.

Milk also has at least some sulfur in it[4], like just about any protein-containing food, but I’m not sure if it’s enough to add to the smell problem.

So, yes, beer and ice cream probably do make gas.

Incidentally, it seems as though methane production in humans only happens in some people. Methane is only produced by certain kinds of archaea, and not all humans have them growing in their intestines along with the regular bacteria. Don’t quote me on this, but I would tend to suspect that this would actually reduce the amount of gas that actually results in the end. Methanogens actually make the methane out of the other two major flatulence gases: carbon dioxide and hydrogen. I haven’t looked up the biochemistry, but I suspect the other byproduct is water. Since the pressure of a particular bubble of gas (and therefore its volume when your container is stretchable, like an intestine) is dependent on the number of actual molecules of any kind of gas in it, if you have methanogenic archaea in your intestines they should be taking a molecule of carbon dioxide plus more than one molecule of hydrogen gas, and producing just one molecule of methane out of it (plus some liquid water), so where you once had three or more molecules of gas you end up with just one. I’m sure somebody somewhere has done some kind of study on this, maybe I’ll go dig for it at some point. While I’m at it, perhaps I should look at patenting the use of archaeal “natural flora” as a probiotic?…

The picture at the head of this post, incidentally, came from this blog post of odd signs – apparently this one’s from an advertisement for some kind of backache treatment. Still, I couldn’t pass up putting it here…

[1] Furne JK, Levitt MD: “Factors influencing frequency of flatus emission by healthy subjects.” Digestive Diseases and Sciences, 1996; 41:8; pp 1631-1635
[2] Rockland LB, Gardiner BL, Pieczarka D: “Stimulation of Gas Production and Growth of Clostridium perfringens Type A (No. 3624) by Legumes.” Journal of Food Science; 1996; 34 (5); pp 411–414.
[3] Cummings JH, Macfarlane GT, Englyst HN: “Prebiotic digestion and fermentation” American Journal of Clinical Nutrition; 2001; 73(2); pp 415-420
[4] Ramsdell GA, Whittier GO: “Composition of Casein in Milk” Journal of Biological Chemistry; 1944; 154; pp 413-419

More Search Amusements. (p.s. I Ain’t Dead Yet.)

A bit longer of a delay between posts than I’d like, but here you go:

+ =?????

I am often amused (and regularly baffled) by the kinds of search queries that lead people to this blog.

I wrote a sloppy little script to parse the server’s access logs and figure out who’s searching for what, where. Since I added the ability to recognize Google Image Searches, it’s gotten even stranger.

I do get a lot of perfectly understandable hits – people looking for information about “heat-fixing slides”, expired jello, and looking for pictures of lactic-acid bacteria or whatnot. Some of them are pretty interesting questions…but first, some oddities.

At the top of my current wierd-o-meter: “carbonated leprechaun”…what??? What’s funnier is that this was a Google Image search – someone doesn’t just want information ABOUT carbonation of leprechauns, they want pictures. Now I can’t stop imagining a mash-up of “Darkman” and Leprechaun. Thanks a lot, whoever you are…”I needs me gold! ARGH! SUNLIGHT! [bubblebubblebubble…]”

Another recent one was just a search for the phrase “new england sucks”. As another Image search. Somebody not only doesn’t like New England, but they want pictures of “new england sucks”?…

Less risible but still kind of funny are searches influenced by unfamiliarity with the English language. I have no idea what the search for pictures related to “useful of DNA” was hoping to find. (Uses of DNA? How to “use” [work with] DNA? Diagrams of genetic processes?). I also see a number of searches just based on the name of the blog – people looking for information about furnishing “big rooms”. I have no idea what the search for “name of thing in room” was expected to turn up. This one’s another language issue, but even taking that into account I’m still baffled about this one. I wouldn’t expect google.de to return any useful information for “Sache im Zimmer” (the original search was actually from a Spanish-speaking area, but No Entiendo Espanol, so I’ll use a German analogy instead.)

Or from Sweden: “Aerobic Oxygen fraud”. Somebody’s figured out that we don’t actually need to breathe and that it’s all a ploy by the Oxygen Lobby to enslave us, I guess.

Maybe just because “chemicals” get mentioned here from time to time, I get the occasional hit from someone looking for illegal drug information (either technical or just news of drug busts or whatever). Note to “HILLBILLY METH” searcher: Hillbillies do moonshine. Meth comes from Rednecks. Jeez, doesn’t everyone have to do a semester of Rural Population Stereotype Taxonomy in college anymore?

There are some more relevant and interesting questions that show up here, too.

Oreo CookieI guess someone in southern California used an interesting analogy in their microbiology class, because I recently got a couple of searches from there looking for why the cell membrane is not like an Oreo® cookie. The answer: There’s no “creme” filling. No seriously – the membrane is two layers of the same kind of molecule stuck together. The phrase you’re looking for is “Phospholipid bilayer”. In a way, the molecules are a lot like detergents – they’ve got one end that “likes” water, and a long tail at the other end that doesn’t (much as oil doesn’t). Since the cell is surrounded by and full of water, you end up with one layer with all its hydrophilic ends touching the water outside the cell, and the other layer with its hydrophilic ends on the inside of the membrane touching the water inside the cell, and the hydrophobic ends of both layers all tangled up together in the middle – without anything between them. See? Not like an oreo cookie at all. Aside from this, cell membranes are also squishier and not chocolate flavored most of the time.

I’ll deal with “does beer and ice cream make gas” in another post later…

#1 on Google!

Over on scienceblogs.com’s The World’s Fair, the author has started an amusing meme.

It goes like this: the challenge is to find 5 sets of search terms for which your own blog or site is the #1 hit on a Google search. Note that it is acceptable to quote specific phrases but of course it’s more impressive if you don’t. Here are 8 that (as I type this) for which this blog is the #1 hit (links go to the blog address that is the hit):

There was at least one other which I’m having trouble remembering at the moment. Perhaps I’ll update later if I remember what it was.

Poor-boy science: should I build my own electrophoresis platform?

I want to build my own little electrophoresis gizmo to play with.

I did pick up a small tube of powdered graphite and some liquid tape. With this, I should be able to make a waterproof electrically-conducting glue that I can use for the electrodes. I’ve got numerous old “wall-wart”-type power adapters that I ought to be able to use for power supply.

The main thing I’m trying to work out in my head before I start trying to actually put this together is exactly how I’m going to arrange it so that I can have either a thin gel or a piece of paper or other fibrous material in between the electrodes so that I can best separate things.

I suppose it’s kind of bizarre, but this is actually part of the ongoing Expired JellO® projects. I was wondering to myself what actual changes might possibly occur in a packet of dry gelatin mix over time, and how would I be able to tell?  My previous experiments have shown no indication that there are any easily detectable differences (no obvious changes in taste or texture, no strange eerie glow, no acquisition of superpowers upon eating it…) so I’ll have to look more closely.

It occurred to me that just maybe over time the strands of protein that make up gelatin might get damaged by oxidation from the air in the pouch (or do they seal the pouch in a relatively inert gas, like argon or nitrogen?). This isn’t something one can really tell just by looking, obviously. One MIGHT be able to tell indirectly by making fresh and “expired” packets of gelatin with the same precisely-measured amount of water, poured on at the same precisely-measured temperature, and ideally with the same amount of mixing. Believe it or not, there are actually special scientific devices for measuring the firmness of gels like this. The hypothesis would be that expired gelatin might end up “degraded” into smaller strands of protein than a fresh packet, and that this would be reflected in a reduced firmness of the gel, or perhaps reduced water-holding capacity.

However, I don’t have access to precise devices for measuring things like that, and in any case since I suspect the difference would be pretty minimal, I’m not sure any difference in firmness would really be detectable with any kind of instrument I could cobble together on my own. What to do?…

I thought that if I had a way to subject a sample of dissolved gelatin to electrophoresis, I could then use a protein-staining substance to see how broad of a range of protein-fragment sizes were existent, or perhaps even spot distinct fragments if oxidative damage tended to happen at the juncture between particular amino acids or something.

I’m not quite sure why, but I have a strong desire to do this experiment from scratch as a “hillbilly biotech” exercise (including building the equipment and obtaining my supplies from grocery or hardware stores rather than specialty scientific supply places).

There are special protein staining compounds I can use at the end to see where my bits of protein ended up after electrophoresis. “Coomassie Brilliant Blue“, for example, but they don’t have that down at the grocery store. (And if you think that’s a funny name for a dye, consider “Light Green SF Yellowish”…)

Then, I ran into a post indirectly about henna over on scienceblogs.com. It seems the natural orange-staining ingredient in henna, called lawsone, may be specifically a protein-staining substance. I’m not certain about this, but a dark-orange protein-staining dye would work for my purposes I think. If so, that solves my need to get a protein stain from an ordinary store.

It’ll be a little while before I can try to put this plan into action, but I think I’ll be able to get to it in the next month or two.

In other news, I think I’ll try to post my “Microbial fuel cells in 90 seconds” audio sometime tomorrow. Then I can work on more. Anybody want to hear me attempting to explain something in 90 seconds? So far I’ve considered MRSA, and perhaps how cow flatulence threatens the world’s climate (which is also a microbiological topic). I’m sure there must be plenty of other possible topics. Any suggestions?

P.S. Who wants audio in Ogg Vorbis format in addition to mp3?

Do Not Taunt Happy Fun Park

Here’s a brief interlude for my new readers. Members of my immediate family have seen this before elsewhere, but what the heck, I may as well share with you all.

Related to my recent posts about this year’s field-trip to Yellowstone National Park, I am reminded of a trip my wife and I took last year to Norris Geyser Basin in the same park.

I’ve heard of “communing with nature”, when the natural world seems to speak to you and put you at ease. Well, on this occasion it didn’t just seem to be speaking to me, and it hardly put me at ease. The conversation between me and the park went something like as follows that day. (Forgive all the scrolling, it WAS a several-hour conversation after all. If it bugs you, feel free to say so in the comments…)

Sign:No Restroom in Geyser Basin

Well, okay, I don’t smoke, I didn’t bring a bicycle, we left the dog at home. And I guess we can hold it until later. It’s a small price to pay to go out to nice, happy, peaceful trails, away from, for example, all the annoying road construction.Traffic cone, in the middle of the trailWow! Look at that! Do I spy the Fruiting Body of the rare Yellowstone Giant Orange Holewarning Mushroom?!?!?No, wait…that’s just a traffic cone over a hole in the trail! What the heck? I thought I was getting away from road construction!

Well. Maybe things will get more natural-looking once we get a chance to walk off into the wilderness. Maybe the map’ll show where we can go.

Map of Norris Geyser Basin, with Warning to Stay On Designated Trails
Ah, look at all the lovely trails. Plenty of space to roam around in.
What? I can’t leave the trails?
sign:Stay On Designated Trails

Can’t I take a mere step or two off? Just a little bit???

Sign:Stay on TrailSign:Stay On WalkYeah, yeah, whatever. What are you going to do if I don’t – have me arrested?

 

Sign:Unlawful to Leave Walkway
What kind of criminal act could possibly be involved with just leaving the silly walkway? Littering? Vandalism?
Sign:It is UNLAWFUL and UNSAFE to: Leave the walkway in thermal areas or throw objects into or deface thermal features

Oh, come on! Look, there’s a beautiful green pool over there, full of no doubt fascinating little animalcules. Can’t I just go over and take a little look?

Sign:Keep Off - Thermal Area
“Thermal Area”? What the heck is that supposed to mean? It’s a little windy and chilly today, maybe I want to be warmed up a little. So, why not? What’s so bad about a “Thermal” area?

Sign:Hazardous Ground - Thin Crust - Boiling Water

What’s that supposed to mean?

 

Sign:Dangerous Ground -with illustration of kid falling into ground and getting broiled-
Children are prone to explode out of the ground unexpectedly?Walkway shown crossing the top of the steaming opening of Green Dragon SpringWhat the heck? Is Green Dragon Spring actually devouring the ground under that walkway?!?! Oh! I get it – you’re saying the park itself can swallow you up and and cook you?
So everything here is flaming hot death, then, right?

Sign:Warning: Trail My Be Icy

Is there no end to the dangers this place threatens innocent visitors with? Can there possibly be anything else this park can do to us?!?!?

 

Solfatara: Very Dangerous Landscape spewing Sulfuric Acid Gas!
“Thin Crust”? “Boiling Water”? Broiled flesh cooked in acid? Ice?
Is this a park, or the kitchen at a Chinese restaurant? Is this how “Hot and Sour Soup” is made?!?!? Is there nothing that can stand in this realm of violent burning chemical death without fear!?!?!?
Fearless Geyser

But what of us poor, fragile fleshy people? We aren’t safe here!That does it! I’m getting out of here! No more of these horrible Killer Thermal Death Areas of Doom for me! I think maybe I’ll just go look at the nice cuddly animals that Yellowstone is also famous for.
Sign: Caution - Wild Animals are Unpredictable and Dangerous!
This whole friggin’ place wants to gore, dismember, maul, cook, devour, and digest me! That does it. No more of this dangerous stuff for me – I think I’ll just go read a nice book for a while…
Bookstore:Closed
NOOOOOOOOOOOOOOOOOOOOOoooo!!!!!!

Libel! Blasphemy! Slander!…

Injustice! Perfidy! HUMBUG!

Periodically, someone puts up a “could you pass a grade-school science class” quiz. The one linked to the image below goes to one that I just broke down and took, purely out of curiousity. Take a look at this outrage!:

JustSayHi - Science Quiz

Oh, sure, it LOOKS good, but what you don’t see is that it only gave me a 96%, implying that I missed one (it was a short quiz)! Sure, the quiz was very much in the modern fashion for “standardized testing” (aka the “No Child Left Awake” project) where the emphasis is on memorizing stuff for a test rather than actual comprehension. So, I thought, maybe I hadn’t correctly memorized which word was correct for one of the word-memorization questions. But, no, according to the “answer sheet”, the one I supposedly got wrong was this one:

(Note: If you’re planning to actually take that quiz, do so now before you read on and I give away one of the answers…)

“How do mammals respire?”

The options were:

  • Aerobically
  • Anaerobically
  • Both aerobically and anaerobically

Come on, I may hardly ever concern myself with perverse eukaryotic systems but…never mind just “mammals”, as far as I know, all eukaryotes (animals, plants, and fungi) only possess aerobic (oxygen-requiring) respiratory systems.

However, the “answer sheet” for the quiz claims that the answer is “Both aerobically and anaerobically”.

So….they’re wrong. I’m pretty sure what what they were intending to ask, given this answer, is “what kind of metabolism do mammals have?”, in which case their answer is correct.

See, “respiration” is only one part of the cellular energy-generating system. Specifically, it’s our friend, the Electron Transport Chain, which (to grossly oversimplify) harnesses the energy of oxygen sucking electrons off the end of the chain various biochemicals to recharge molecules of ATP. That’s not the only way a cell can get ATP, though. What the quiz authors are presumably alluding to is that there are non-oxygen-requiring biochemical pathways that animal cells can take to make energy – such as the one your muscles use when they can’t get enough oxygen, which involves production of lactic acid, which in turn gets blamed for the “burn” sensation you get when you work your muscles hard.

So, the authors of this quiz are bad, bad people, besmirching my reputation and harming my precious self-esteem by giving me less than 100% on that quiz!

On a related subject: breathing causes cancer in Sprague-Dawley™ rats!

No, seriously, it’s true – try raising one group of Sprague-Dawley™ rats with air, and one group with no air, and examing both populations 150 days later. I guarantee you’ll find many more cancerous growths in the “with air” group than in the group that was denied air to breathe…

What brought this outburst on? It was this blog article. “No, It’s for Real: Aspartame Causes Cancer”, the post proclaims. They’re talking about This study(pdf). Go ahead, take a look, but in particular, look at the tables of actual data, not the paper’s abstract. In particular, take a look at Figure 1, especially “D” and “E” (showing survival rates for the different groups of Sprague-Dawley™ rats as the study progressed), and at the number of “tumor-bearing animals” in Table 2.

Notice that at around 120 days on the survival graphs, the groups with the highest percentage of members still alive were the groups receiving the most aspartame in their feed. It’s worth noting that the highest-Aspartame group there was getting roughly the equivalent of a human drinking <em>thousands</em> of cans of diet soda every day. Also note, in fairness, that both graphs seem to show little difference between the groups, so rather than assuming that Aspartame makes Sprague-Dawley™ rats live longer, I would tend to assume that there’s really not much difference.

Notice also that in terms of the percentage of Sprague-Dawley™ rats that developed one or more tumors, there were fewer of them in the group that got the equivalent of 500 mg/kg of aspartame: which scaled up to human terms means about 200-250 cans of diet soda EVERY DAY worth of aspartame.

You may be wondering why I keep mentioning Sprague-Dawley™. It’s because this is a particular commercially-bred strain of rat that’s popular with labs for this kind of thing. One point that isn’t always mentioned is this: Sprague-Dawley™ rats are known to be prone to developing cancer spontaneously. This can be handy if you’re doing studies of “borderline” carcinogens. The hope is that if something has even a tiny ability to cause cancer, you’ll be able to measure the effect in a population of critters known to get cancer at the drop of a metaphorical hat, when in a human population the incidence might be so rare that you can’t distinguish it from random chance. To my admittedly-not-big-on-the-biochemistry-of-perverse-eukaryotes mind, this study really seems to show that there’s little or no effect – and certainly no dose-dependent effect – of aspartame even on cancer-prone lab rats.

I don’t know what it is, but “artificial sweeteners”, and especially aspartame, seem to generate such passionate hatred in some people. It reminds me a great deal of people’s reactions to “genetically modified” crops. People just really want to hate it. The authors of this paper are obviously trying REALLY hard to show somehow that aspartame is a dangerous poison, despite the inconclusive-appearing actual results. Though I suppose one could argue that they showed Aspartame to be at least as much of a deadly poison as Expired JellO®.

And now that I have exposed my readers to several times the Recommended Daily Allowance of Humbug, I bid you all a good night – I have Art History and Philosophy to attend in the morning…