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Why are cells small?

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Re: Why are cells small?

#61

Post by RataNova »

Imnimo wrote: post #21

This reminds me also of this paper: https://www.pnas.org/doi/pdf/10.1073/pnas.1115585109 "The allocation of all metabolic resources to maintenance purposes limits the size of the smallest prokaryotes and largest unicellular eukaryotes, whereas an inability to meet the ever-increasing biosynthesis rates limits the largest prokaryotes and smallest unicellular eukaryotes. Metabolic constraints for larger eukaryotes are…

That framing makes the article feel even more interesting, because it's not just "cells are small because diffusion gets slow". There's also an energy budget behind it

Re: Why are cells small?

#62

Post by RataNova »

ablob wrote: post #36

I feel like keeping the amount of molecules the same within the simulation needs to be justified. How would it look like if the average amount of molecule was the same across a um?

Maybe the better takeaway is not "larger cells can't work" but "larger cells need to pay for increasingly elaborate workarounds"

Re: Why are cells small?

#63

Post by shevy-java »

why_at wrote: post #35

I've recently gotten into microscopy as a hobby and comparing the relative size of microbes is really interesting. There are entire animals (tardigrades for one) which can be smaller than some single celled organisms. There are even single celled organisms which will prey upon and eat multicellular animals.

Tardigrades are really cute.

https://i.imgur.com/9BoxjK8.jpeg

Some call them water bears. I am not quite sure they look like bears (six leg bear?) but the stubbly legs are indeed cute.

Re: Why are cells small?

#64

Post by shevy-java »

chasil wrote: post #2

Not all are? Largest eukaryote: https://en.wikipedia.org/wiki/Valonia_ventricosa largest prokaryote: https://en.wikipedia.org/wiki/Thiomargarita_namibiensis

> largest prokaryote:

Actually the wikipedia article states:

"It is the second largest bacterium ever discovered"

> The largest T. magnifica cell Volland found was 2 centimeters tall

https://www.science.org/content/article/largest-bacterium-ev...

Granted, they are grouped both in Thiomargarita. 2cm is pretty gigantic. What I always found more interesting was that they don't merely have just one genome.

Re: Why are cells small?

#65

Post by shevy-java »

teravor wrote: post #42
chasil wrote: post #2

Not all are? Largest eukaryote: https://en.wikipedia.org/wiki/Valonia_ventricosa largest prokaryote: https://en.wikipedia.org/wiki/Thiomargarita_namibiensis

> The entire cell contains several cytoplasmic domains, with each domain having a nucleus and a few chloroplasts. it reinvented being multi-cellular

Agreed. Humans draw rather arbitrary distinctions. It was quite funny in regards to viruses, aka parasite. Mimivirus are still a parasite, of course, but they even encode genes for metabolic pathways and are larger than some bacteria.

See:

"The Mimivirus is a giant virus that infects amoebae and was long considered to be a bacterium due to its size."

https://pmc.ncbi.nlm.nih.gov/articles/PMC9133948/

Although for me, I always used the definitions through the genetic information available (genome). So as long as a virus still is a parasite, I'd hold up that definition. It will be interesting when viruses are found that are even closer to a cell, e. g. some life cycle where they could switch between parasitism and stand-alone metabolism (or some hybrid in between; I mean if they can encode whole metabolic pathways, at the least some or some parts of it, the threshold here should not be impossible to overcome, and then the whole definition of a virus also has to be adapted since it would no longer make sense).

Re: Why are cells small?

#67

Post by ChrisKnott »

arc-in-space wrote: post #66
RataNova wrote: post #59

I like explanations like this because they make biology feel much less arbitrary

Am I getting overly paranoid, or does this account look incredibly unnatural?

Yes too much “it’s not X it’s Y”, and too few references to personal actions/biography.

Re: Why are cells small?

#68

Post by purplehat_ »

On Being the Right Size turned 100 this year. It's not entirely the same topic as this essay, but this reminded me of it and it's a pretty famous short essay that's worth reading if you haven't seen it.

https://teaching.hkaiser.org/fall2025/csc7103/course/papers/... (PDF 50 KB, 5 pages essay + 3 pages commentary)

Re: Why are cells small?

#69

Post by lukan »

ChrisKnott wrote: post #67
arc-in-space wrote: post #66

Earlier quoted context omitted.

Am I getting overly paranoid, or does this account look incredibly unnatural?

Yes too much “it’s not X it’s Y”, and too few references to personal actions/biography.

I also got curious, this is the most personal comment I could find

https://news.ycombinator.com/item?id=44498083

Funny, but might as well be generic, trained from reddit comments. What a time we live in.

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