What is the biggest single-celled organism? – Murry Gans
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What is the biggest single-celled organism? – Murry Gans


The elephant is a creature
of epic proportions, and yet it owes its enormity to more
than 1,000 trillion microscopic cells, and on the epically small end of things, there are likely millions
of unicellular species, yet there are very few we can see
with the naked eye. Why is that? Why don’t we get unicellular elephants, or blue whales, or brown bears? To find out, we have to peer into
a cell’s guts. This is where most
of the cell’s functions occur, enclosed by a cellular membrane that acts as the doorway into
and out of the cell. Any resources the cell needs to consume, or waste products it needs to expel, first have to pass through this membrane. But there’s a biological quirk
in this set up. A cell’s surface and volume increase
at different rates. Cells come in many shapes, but imagining them as cubes will make
the math easy to calculate. A cube has six faces. These represent the cell membrane,
and make up its surface area. A cube measuring one micrometer
on each side, that’s one millionth of a meter, would have a total surface area
of six square micrometers. And its volume would be
one cubic micrometer. This would give us six units
of surface area for every single unit of volume, a six to one ratio. But things change dramatically
if we make the cube ten times bigger, measuring ten micrometers on each side. This cell would have a surface area
of 600 square micrometers and a volume of one thousand
cubic micrometers, a ratio of only .6 to one. That’s less than one unit of surface area
to service each unit of volume. As the cube grows, its volume increases
much faster than its surface area. The interior would overtake the membrane, leaving too little surface area for things
to quickly move in and out of the cell. A huge cell would back up with waste
and eventually die and disintegrate. There’s another plus to having multitudes
of smaller cells, too. It’s hardly a tragedy if one gets
punctured, infected, or destroyed. Now, there are some
exceptionally large cells that have adapted to cheat the system, like the body’s longest cell, a neuron that stretches from the base
of the spine to the foot. To compensate for its length,
it’s really thin, just a few micrometers in diameter. Another example can be found
in your small intestine, where structures called villi
fold up into little fingers. Each villus is made of cells with highly
folded membranes that have tiny bumps called microvilli
to increase their surface area. But what about single-celled organisms? Caulerpa taxifolia, a green algae
that can reach 30 centimeters long, is believed to be the largest
single-celled organism in the world thanks to its unique biological hacks. Its surface area is enhanced with
a frond-like structure. It uses photosynthesis to assemble
its own food molecules and it’s coenocytic. That means it’s a single cell
with multiple nuclei, making it like a multicellular organism
but without the divisions between cells. Yet even the biggest unicellular organisms
have limits, and none grows nearly as large
as the elephant, whale, or bear. But within every big creature
are trillions of minuscule cells perfectly suited in all their tininess to keeping the Earth’s giants
lumbering along.

100 thoughts on “What is the biggest single-celled organism? – Murry Gans

  1. Guys… A single celled bear would be tiny yea? And wouldn’t that make a fantastic house pet? A tiny blue whale in a fish tank… that would be awesome too! But this is never gonna happen 😛

  2. The cell body of a motor neuron is approximately 100 microns (0.1 millimeter) in diameter and as you now know, the axon is about 1 meter (1,000 millimeter) in length. So, the axon of a motor neuron is 10,000 times as long as the cell body is wide.

  3. Actually, no. The biggest unicellular organism is Xenophyophorea. They can reach 20cm of diameter.

    https://en.m.wikipedia.org/wiki/Xenophyophore

    The biggest Xenophyophorea is Syringammina Fragilissima

  4. I have caluerpa taxifolia in my sump. Ìt's beautiful but toxic to the fishes. It is banned in many countries and States of USA.

  5. Despite being incredibly tiny, unicellular organisms are also massively complex. And the human body has trillions of these hyper complex machines working to do so many different uncountable functions at any one time.

    My question: If a bunch of atoms were to suddenly merge such that it made an atom by atom replica of me and had enough energy to keep going, would it be able to reproduce with us?

    If so, should it be considered a living human being?

  6. Correct me if I am wrong but i am a bit confused about the surface area to volume ration discussed at 1:18. I do not see the reasoning behind this guys logic. So, he is saying that a regular shape, that has been dilated to a certain sizes will have a shifted surface area to volume ratio? And if he is saying that it would make this hypothetical situation true.

    So take a 1 mm cube (and just so you guys know that is millimetre not micrometer the abbreviation was wrong in the video the abbreviation for micrometre is µm so what the hark Ted-ed? It really was pretty annoying to see the wrong abbreviations.) So taking this 1 mm by 1 mm cube you will get a total surface area of 6 mm² and a total volume of 1mm³ (a 6:1 ratio). So using his next example a cube that is 10 mm by 10 mm by 10 mm, we get a 1 cm cube. This makes sense since 10 mm is 1 cm. Next, we can see that a 1 cm cube has a surface area (not surprisingly) of 6 cm² and 1 cm³. So, we are back to the 6:1 ratio.
    So if we created x system of measure could you always keep the ratio (volume to surface area) of a cube 6:1?

    Overall the explanation in the video seems inconsistent can someone answer my question?

  7. based on the title, I was hoping you dive deeper than just talking about 1 large single cell organism. give more examples man, disappointing clickbait

  8. Wait …
    I expected that the slime mold might be the largest single cell. I mean … That is like an giant amoeba!

  9. As for that bit about the surface area and volume of a cell, I’ve heard it called the square/cube law; basically, an object’s surface area scales with the square of its length, but the volume scales with its cube, so the latter increases more when an object is scaled up. Just thought they could have explained that better.

  10. On land today, the biggest single celled organism is an ostrich egg, in the ocean i would hazard a jelly fish, in thw invisible world i would guess an amoeba……!!!!

  11. Another aspect you didn’t mention is the radical difference in how things move in the microscopic and macroscopic world’s (I think there’d a Ted-Ed about Reynolds numbers, great additional material); the way animals like the elephants and grizzly bears you mentioned eat and move and reproduce involves a whole mess of rigid skeletons and muscles and specialized cells that likely would be impossible for a unicellular creature to mimic, while a cell’s tricks with microtubule “skeletons” and flagellae would not work at macroscopic scales.

  12. I remember an experiment we did in science class once to demonstrate the difficulty presented by volume increasing faster than surface area. We cut 2 cubes of some kind of gel, one big and one small, and out them in a colored water solution and left them over night. When we cut them open the next day, the smaller cubes were mostly saturated but the larger ones were not.
    This applies to cells because they rely a lot on the passive diffusion of water (osmosis) in order to save energy. It would take a lot of energy to speed up the transfer of chemicals by using a process other than osmosis.

  13. "what is the biggest single-celled organism?" is now interrupted by "W0W0W0W0W0 ELEPHANTS ARE HUUGEEEE CHECK OUT THE CELLS ON THIS THING W 0 0 0 W"

  14. Question : But what are Tess's initial dimensions ??? … Since we know the final ones well !!! … ( Height 5' 4¼" (1,63 m) ) …

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