# Are we really all no more than 2 years old? **URL:** \ **Category:** Factual Questions\ **Created:** [July 15, 2004, 1:51am UTC](https://boards.straightdope.com/t/are-we-really-all-no-more-than-2-years-old/255192 "2004-07-15T01:51:52Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [July 15, 2004, 4:33pm UTC](https://boards.straightdope.com/t/are-we-really-all-no-more-than-2-years-old/255192/21 "2004-07-15T16:33:21Z")
[Hydrogen exchange and the dynamic structure of proteins.](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6757714&dopt=Abstract) [Protein turnover:](http://www.aw-bc.com/mathews/ch20/c20pt.htm) > [@](#): > > In a typical day, a person who is in nitrogen balance will consume 100 grams of protein, break down 400 grams of bodily protein, resynthesize 400 grams of protein, and excrete/catabolize 100 grams. Individual proteins exhibit tremendous variability in their metabolic lifetimes, from a few minutes to a few months. Protein degradation obeys first order kinetics. For a particular protein, individual molecules are degraded at random, such that a semilogarithmic plot of isotope remaining in a protein versus time is linear. Thus, we can determine the metabolic half-life of a particular protein. In a rat the average protein has a half-life of 1 or 2 days. ---
**Author:** ![KP](https://avatars.discourse-cdn.com/v4/letter/k/a9adbd/32.png) [@KP](https://boards.straightdope.com/u/KP)\ **Post date:** [July 15, 2004, 6:38pm UTC](https://boards.straightdope.com/t/are-we-really-all-no-more-than-2-years-old/255192/22 "2004-07-15T18:38:44Z")
> [@](#): > > Does anybody have any idea how this question applies specifically to brain and other nervous cells?? While I can’t give you a specific answer, I can tell you where to look. There have been a large number of studies using radioisotopes as nutrients for nerve tissue (often in vivo) or initial growth substrates for neural tissue cultures. The solid component of neuron is almost entirely carbon, nitrogen, oxygen and hydrogen, and each of these has a commonly used, relatively harmless medical research isotope with a long enough half life (and other useful properties allowing them to be distinguished by e.g. NMR imaging) that we can observe atomic turnover directly. Such studies were common in biochemistry through the 1950s/60s Once we had the outline of cell processes, radiolabelling experiments were still important, but they were more specialized. e.g. manufacturing radio-glucose with a C-14 atom instead of C-12 at a specific site to determine the diffusion, uptake and metabolism of the sugar, the fate of each specific atom in the molecule, etc. While radioisotopes have slightly different reaction rates than the most common “stable” isotope, due to their slightly higher (usually) mass, they still gave us a reasonable estimate, which could be refined later by comparing the rate of each individual (enzyme catalyzed) reaction with both isotopes. ---
**Author:** ![vetbridge](https://avatars.discourse-cdn.com/v4/letter/v/b5e925/32.png) [@vetbridge](https://boards.straightdope.com/u/vetbridge)\ **Post date:** [July 15, 2004, 10:22pm UTC](https://boards.straightdope.com/t/are-we-really-all-no-more-than-2-years-old/255192/23 "2004-07-15T22:22:06Z")
> [@x-ray vision](#): > > I’m going with epiphany. Damn you! Epiphany told me she wasn’t seeing anyone else. Does she ever mention me? ---
**Author:** ![legion](https://avatars.discourse-cdn.com/v4/letter/l/838e76/32.png) [@legion](https://boards.straightdope.com/u/legion)\ **Post date:** [July 15, 2004, 10:53pm UTC](https://boards.straightdope.com/t/are-we-really-all-no-more-than-2-years-old/255192/24 "2004-07-15T22:53:59Z")
> [@vetbridge](#): > > Damn you! Epiphany told me she wasn’t seeing anyone else. Does she ever mention me? Maybe. Is your name Eureka? ---
**Author:** ![vetbridge](https://avatars.discourse-cdn.com/v4/letter/v/b5e925/32.png) [@vetbridge](https://boards.straightdope.com/u/vetbridge)\ **Post date:** [July 15, 2004, 11:08pm UTC](https://boards.straightdope.com/t/are-we-really-all-no-more-than-2-years-old/255192/25 "2004-07-15T23:08:35Z")
> [@legion](#): > > Maybe. Is your name Eureka? Nope, she always refered to me by my nickname, “I’mcoming”. 😉 ---
**Author:** ![ltfire](https://avatars.discourse-cdn.com/v4/letter/l/7ea924/32.png) [@ltfire](https://boards.straightdope.com/u/ltfire)\ **Post date:** [July 15, 2004, 11:50pm UTC](https://boards.straightdope.com/t/are-we-really-all-no-more-than-2-years-old/255192/26 "2004-07-15T23:50:42Z")
> [@Qadgop the Mercotan](#): > > Epidural? Epiphyseal fracture? episcleritis? Episiotomy? Epispadias? Epistaxis? Epithalamus? Epithelial cyst? I just had an epistaxis looking up all those other words at WebMD. Damn you, QADGOP. 😃 ---
**Author:** ![kniz](https://avatars.discourse-cdn.com/v4/letter/k/c37758/32.png) [@kniz](https://boards.straightdope.com/u/kniz)\ **Post date:** [July 16, 2004, 1:09am UTC](https://boards.straightdope.com/t/are-we-really-all-no-more-than-2-years-old/255192/27 "2004-07-16T01:09:45Z")
I’ve said this before; I’m saying it again; and it most likely will come up again, but… **It must be awful lonesome on the Isle of Man.** 😉 ---
**Author:** ![Lobsang](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lobsang/32/4067_2.png) [@Lobsang](https://boards.straightdope.com/u/Lobsang)\ **Post date:** [July 16, 2004, 1:16am UTC](https://boards.straightdope.com/t/are-we-really-all-no-more-than-2-years-old/255192/28 "2004-07-16T01:16:53Z")
Babysitting computers is lonely work. [Previous page](https://boards.straightdope.com/t/are-we-really-all-no-more-than-2-years-old/255192.md?page=1)