Cells to Contemplate

Cells are truly life’s building blocks. Everything we are as humans, everything that makes up a plant is either a cell or extruded from a cell. And each of us is made of trillions of cells. Heck – a typical wine cork is made of nearly 300,000,000 cells. So most cells are pretty small.

What do I mean by small; how do we measure that? Let’s start with the world standard for physical size, the meter. Or if we are talking about most of the world, we mean the metre (m), which is a bit longer than the archaic “yard” that continues to deprecate American engineering and architecture. But for biologists, a yard is either the surround to a house, or a measure of beer. The metre is standard in science throughout the world, because the metric system is functionally superior to the anachronistic inch and foot standards. Scientists measure things using the metric system.

Metres are good for taking stock of trees, but a more useful dimension for measuring leaves and seed would be the millimetre (mm), 1,000th of a meter. A millimetre is slightly more than the thickness of a credit card. Hair (including beard, of course) grows a millimetre every two to three days.

Most cells are much smaller than that.  Cell biologists typically measure cell size using micrometers (µm); one µm is 1,000th of a millimetre.  Red blood cells are 6-8 µm across. Bacteria range from 1-10 µm long. Typical plastic cling wrap is 10-15 µm thick.  

Cotton full boll ABA_7581 reduced But some cells break the rules.  Cotton fibers, whether fair, middling, good, or choice, are monstrous cells.  A single Cotton fiber is one cell that grew from the surface (epidermis) of a cotton seed, commonly elongating to around 2.5 cm (translation: 25,000 µm) –  gargantuan compared to most other kinds of cells – 25 thousand times as long as a small bacterium, 7,500 times longer than the diameter of a red blood cell.  It’s amazing, astonishing.  It is the fabric of our lives.

That is especially true when you think back to our wine cork.  Cells that make up cork are 15-50 µm across, which means a Cotton cell is about a thousand times longer than a cork cell.  At that rate, it becomes easier to see how one wine cork might be made of 300 million cells.

Candace H. Haigler, Lissete Betancur, Michael R. Stiff, and John R. Tuttle, 2012, Cotton fiber: a powerful single-cell model for cell wall and cellulose research. Front Plant Sci. 2012 3: 104. Published online 2012 May 21. doi: 10.3389/fpls.2012.00104, PMCID: PMC3356883 PMID: 22661979

Lorna Gibson, 2016. “Cork: Structures, Properties, Applications” http://arnoldia.arboretum.harvard.edu/pdf/articles/2016-74-1-cork-structure-properties-applications.pdf

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