The Weight of a Cell
asimov.press91 points by arbesman 3 days ago
91 points by arbesman 3 days ago
> A typical kitchen scale has a sensitivity of 0.1 grams
As someone who's been looking for a good kitchen scale, your typical kitchen scale is actually precise to then nearest gram at best, and in terms of precision it's probably not very precise at all. 0.1g is rare, and these usually cost more, especially if they're actually reliable.
They're not even that expensive anymore, you can find pretty reasonably priced ones: https://www.amazon.com/dp/B0D66X8B5B/ref=sspa_dk_detail_2?pd...
I have the ooni one that i use for my baking and to measure yeast and it was one of the best investments i made.
Probably fine, but I've had some poor experiences with those kinds of Chinese drop-shipped electronics that floods Amazon these days.
> 0.1g is rare, and these usually cost more, especially if they're actually reliable.
You can buy a coffee scale for $10-$20 that has 0.1g to 2000g or 3000g accuracy. I run a cafe and have tested these using our much more expensive scales, they are accurate. Not suitable for high volume commercial use but probably good enough at home if you're on a budget.
You should also check on the back of the scales how the accuracy changes across it's range, they'll often be accurate to 0.1g up to 1000g, and then accurate to 1g for the rest of the range. This includes expensive scales.
Most of the budget scales I've seen are accurate to <0.1g. If in doubt, grab a cheap set of calibration weights for $20, I have 2 sets from China and both are accurate to <0.01g on all the weights from 1g up to 200g.
Obviously if you have the money, you can buy actual certified ASTM weights, but they are insanely expensive.
You can calibrate the scale with coins as well. They have a pretty well defined mass.
Many countries don't have coins unfortunately, including the one where I live. Also, is that true for all coins in every country?
Coffee specific scales typically are around 0.1g accurate. They are a little more expensive, but certainly not unobtainable.
I would have thought that, but about a year ago I have replaced my old kitchen scale with a 1-gram-resolution with a kitchen scale having 0.1-g resolution.
This kitchen scale was cheap, perhaps $10, and it is made by some no-name Chinese company, but despite that it has proved to be much more accurate than I had expected.
I have checked it with various standard weights between 5 gram and 500 gram, and all of them were displayed correctly, usually with no more than 0.1 g difference. At most there may have been a 0.2 g error once. Most of the standard weights were displayed exactly. I assume that the kitchen scale is calibrated in the factory with a standard weight, and it has good linearity, so it is expected that if one weight is displayed correctly, all the others will also be correct. So what is significant is that it has not drifted since the factory calibration, not even after more than a year later, because I have rechecked it.
The higher resolution has been very helpful with some things that I weigh every day. For instance, when I weigh every day with it 50 grams of something and 125 grams of something else, both being taken for 1-kilogram packages, I can be pretty certain that the first package will suffice for 20 days and the second package will suffice for 8 days, and in the last day for each package I will still use the normal quantity of that product.
With the previous lower resolution kitchen scales, the accumulated 1-gram errors were enough so that in the last day there would remain an abnormal amount of product in the package.
The only disadvantage of the higher-resolution kitchen scale it that it can weigh only up to 3 kg, while the previous kitchen scale could weigh up to 5 kg. However, I normally cook only for myself, therefore I very rarely need to weigh something above 1 kg, so the lower maximum limit did not matter.
I usually need to tare on much heavier weights than what I actually measure, like cooking pots. 5 kg max weight comes in handy for that.
> your typical kitchen scale is actually precise to then nearest gram at best
Do you mean accuracy or precision? If you get the same measurement from the same scale twice, that’s precision. However, it might not be accurate.
Good points. I mean both! I have a German Soehnle scale, supposedly a good, old reliable brand, that randomly fluctuates between +1 and -1 grams while it's just sitting there.
I hadn't thought about this, but this is probably why in baking recipes where amounts of flour, sugar, etc. are specified by weight, baking powder and any spices will be specified by volume.
Of course this is all false precision once you start adding eggs.
imo the reason to bake by weight is because the ratios of the major ingredients (flour, fat, sugar, and water) determines the properties of the dough, and it's impossible to measure by volume reliably (especially flour, which is the largest ingredient by weight in most recipes). Meanwhile you don't have to be precise with baking soda or yeast. Mix-ins like herbs are completely to taste. Salt could go either way.
Recipes absolutely adjust for the weight of the eggs and some rules of thumb for water and fat content. But that said, a chicken egg is like 55g with 10% tolerance (at least the eggs I buy, and I do everything by weight). 5g of mostly water one way or the other doesn't have a massive amount of impact on the dough, and you can always adjust based on feel after mixing.
At scale everything is measured by weight fairly precisely. But you really don't care about accuracy, since it's the ratios of ingredients that make the product and not the raw amounts.
Eggs are actually fairly well defined on weight. And absolutely are better defined than things like flour where a volumetric cup can be 4oz or 12oz (or more) depending on how fluffed the flour is and individual scouping technique.
Honestly, you don't want them too precise.
0.1 gram is definitely the sweet spot for kitchen though, measuring salts, supplements, baking,that extra .1g comes in handy.
I got an Ohaus Scout 0.01g scale, and it's so sensitive it's almost a thermometer. You can literally blow on it softly and the scale starts fluctuating wildly.
Some surprising science fact that many people don't know, an animal egg (chicken, birds, etc) is a single cell, so there's a huge variability in the weight of a cell.
There are some very large single celled organisms that aren’t eggs. E.g.:
https://en.wikipedia.org/wiki/Valonia_ventricosa
https://en.wikipedia.org/wiki/Foraminifera
Even some bacteria can grow to visible size:
https://en.wikipedia.org/wiki/Thiomargarita_magnifica
There are some other examples here:
I found this claim unbelievable, but it is mostly true. It isn't quite the whole egg, it is just the yolk. But that's still a very large cell!
http://cnet.com/home/kitchen-and-household/appliance-science... verifies this.
It's analogous to the mammalian egg, but a lot bigger. (And IIRC the egg is the largest cell in humans.)
Very cool. I wonder how the accuracy of weighing a single cell would compare to counting a huge number of cells (let's say 10^9) and doing a bulk weight measurement. The problem would shift to being able to accurately count cells, and being able to exclude the effects of liquid trapped in between the cells.
Cool results and methods, but I'll disagree with one of the article's statements.
In talking about the work done on e. coli, a non spherical cell, it says the methods had to be changed due to "turbulence" attendant to the e. coli's departure from sphericity of the earlier tested yeast cells.
My rough calcs show a Reynolds number in the range of 1e-6. The onset of turbulence happens at Reynolds numbers of ~2300 for pure water. The 1% sugar solution would have a negligibly higher turbulence onset Reynolds number.
I expect the need for different methodology wasn't turbulence, but the difference in drag presented by an elongated e. coli compared to a spherical yeast cell.
I've built a scale with a kHz sampling rate and gram precision at +/-100kg range.
One thing I found out is that getting calibrated accuracy beyond 0.1% is hard and expensive despite having all that precision.
What happens when something is put on the scale while it's sampling? Does the curve depend on properties of the scale, or just properties of the object and the manner in which it was put on the scale?
It's the latter. The scale is meant for real-time monitoring of rapidly varying force (the primary application is about monitoring the force derivative and repeatable max force logging). It uses an aluminum load cell if you're familiar with those, there's a tad of a multi-kHz resonance that is typically overshadowed by the object properties.
use a resonant determination of mass.
https://www.nature.com/articles/nnano.2012.42
https://arstechnica.com/science/2012/04/measuring-yoctogram-...
Asimov really is a breath of fresh air. Love their content
> Cells are physical objects
This might sound trivial, but in me sparks a much larger point: which kinds of experimental designs and tests might we miss when engaging in a special science? In establishing dedicated methods I think it's highly likely for there to be low-hanging fruits of experimental setups not considered due to prevalence of these very specific frameworks.
Not sure I am tracking your point entirely, but any time I start digging into a new domain I regularly find that the language peculiar to that topic can hide concepts that are broadly familiar and, in part, exacerbate the problem that (I think) you are describing.
This seems like the non-Substack link: https://press.asimov.com/articles/cell-weight.
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