Editing Surface area (section)

== In biology ==
[[Image:Mitochondrion 186.jpg|right|thumb|The [[inner membrane of the mitochondrion]] has a large surface area due to infoldings, allowing higher rates of [[cellular respiration]] (electron [[micrograph]]).<ref>{{Cite journal |last1=Paumard |first1=Patrick |last2=Vaillier |first2=Jacques |last3=Coulary |first3=Bénédicte |last4=Schaeffer |first4=Jacques |last5=Soubannier |first5=Vincent |last6=Mueller |first6=David M. |last7=Brèthes |first7=Daniel |last8=di Rago |first8=Jean-Paul |last9=Velours |first9=Jean |date=2002-02-01 |title=The ATP synthase is involved in generating mitochondrial cristae morphology |url=http://emboj.embopress.org/cgi/doi/10.1093/emboj/21.3.221 |journal=The EMBO Journal |language=en |volume=21 |issue=3 |pages=221–230 |doi=10.1093/emboj/21.3.221 |pmc=125827 |pmid=11823415}}</ref>]]
The surface area of an organism is important in several considerations, such as regulation of body temperature and [[digestion]].<ref>{{Cite journal |last=Narasimhan |first=Arunn |date=2008-07-01 |title=Why do elephants have big ear flaps? |url=https://doi.org/10.1007/s12045-008-0070-5 |journal=Resonance |language=en |volume=13 |issue=7 |pages=638–647 |doi=10.1007/s12045-008-0070-5 |issn=0973-712X|url-access=subscription }}</ref> Animals use their [[teeth]] to grind food down into smaller particles, increasing the surface area available for digestion.<ref>{{Citation |last=Feher |first=Joseph |title=Mouth and Esophagus |date=2012 |work=Quantitative Human Physiology |pages=689–700 |url=https://doi.org/10.1016/B978-0-12-382163-8.00077-3 |access-date=2024-03-30 |publisher=Elsevier |doi=10.1016/b978-0-12-382163-8.00077-3|isbn=978-0-12-382163-8 |url-access=subscription }}</ref> The epithelial tissue lining the digestive tract contains [[microvilli]], greatly increasing the area available for absorption.<ref>{{Cite web |title=Microvillus {{!}} Description, Anatomy, & Function {{!}} Britannica |url=https://www.britannica.com/science/microvillus |access-date=2024-03-30 |website=www.britannica.com |language=en}}</ref> [[Elephant]]s have large [[ear]]s, allowing them to regulate their own body temperature.<ref>{{Cite journal |last=Wright |first=P. G. |date=1984 |title=Why do elephants flap their ears? |url=https://www.ajol.info/index.php/az/article/view/152820 |journal=African Zoology |language=en |volume=19 |issue=4 |pages=266–269 |issn=2224-073X}}</ref> In other instances, animals will need to minimize surface area;<ref>{{Cite journal |last1=Stocks |first1=Jodie M. |last2=Taylor |first2=Nigel A.S. |last3=Tipton |first3=Michael J. |last4=Greenleaf |first4=John E. |date=2004-05-01 |title=Human Physiological Responses to Cold Exposure |url=https://www.ingentaconnect.com/content/asma/asem/2004/00000075/00000005/art00011 |journal=Aviation, Space, and Environmental Medicine |volume=75 |issue=5 |pages=444–457|pmid=15152898 }}</ref> for example, people will fold their arms over their chest when cold to minimize heat loss.

The [[surface area to volume ratio]] (SA:V) of a [[cell (biology)|cell]] imposes upper limits on size, as the volume increases much faster than does the surface area, thus limiting the rate at which substances diffuse from the interior across the [[cell membrane]] to interstitial spaces or to other cells.<ref>{{Cite journal |last=Deaver |first=James R. |date=1978-11-01 |title=Modeling Limits to Cell Size |url=https://online.ucpress.edu/abt/article/40/8/502/11842/Modeling-Limits-to-Cell-Size |journal=The American Biology Teacher |language=en |volume=40 |issue=8 |pages=502–504 |doi=10.2307/4446369 |jstor=4446369 |issn=0002-7685|url-access=subscription }}</ref> Indeed, representing a cell as an idealized [[sphere]] of radius {{mvar|r}}, the volume and surface area are, respectively, {{math|1=''V'' = (4/3)''πr''<sup>3</sup>}} and {{math|1=''SA'' = 4''πr''<sup>2</sup>}}. The resulting surface area to volume ratio is therefore {{math|3/''r''}}. Thus, if a cell has a radius of 1 μm, the SA:V ratio is 3; whereas if the radius of the cell is instead 10 μm, then the SA:V ratio becomes 0.3. With a cell radius of 100, SA:V ratio is 0.03. Thus, the surface area falls off steeply with increasing volume.