# Technical obstacles in getting humans to photosynthesize? **URL:** \ **Category:** Great Debates\ **Created:** [October 5, 2004, 6:31pm UTC](https://boards.straightdope.com/t/technical-obstacles-in-getting-humans-to-photosynthesize/267695 "2004-10-05T18:31:47Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [October 5, 2004, 6:31pm UTC](https://boards.straightdope.com/t/technical-obstacles-in-getting-humans-to-photosynthesize/267695/1 "2004-10-05T18:31:47Z")
Assuming, for the moment, that we could create dermal cells with chloroplasts in them, which seems eminently possible considering the genetic engineering we have been doing lately. I did the math, and according to chlorophyll’s efficiency versus how much light would hit you in a well-lit place, having photosynthetic skin could gain you several hundred calories per day: not enough to live on but perhaps prolonging life or avoiding starvation in marginal caloric situations. So: Did I do the math wrong (I assumed around %30 chlorophyll efficiency and absorbing light from a prone position)? What other obstacles would lie ahead, such as: – Need to regulate the chloroplasts (I don’t know how much structure there is in eukaryotes to regulate their chloroplasts and mitochondria, versus how independent they are.) – Need to use the rest of plants’ coping strategy vis a vis free radicals (for instance, would we have to megadose on carotenes in order to avoid cancer, since the process of photosynthesis involves massive free radicals?) – Problems in getting the sugar from the skin into the body (I assume that if Vitamin D can do it, sugar would do it also?) ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [October 5, 2004, 6:40pm UTC](https://boards.straightdope.com/t/technical-obstacles-in-getting-humans-to-photosynthesize/267695/2 "2004-10-05T18:40:55Z")
Were they calories or Calories? ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [October 5, 2004, 7:03pm UTC](https://boards.straightdope.com/t/technical-obstacles-in-getting-humans-to-photosynthesize/267695/3 "2004-10-05T19:03:48Z")
Well I tried this 1500 Cals = 6000kJ Over 24 hrs that mean you radiate about 70W So we need to receive a significant portion of our power from light Incident Light is 900W/m[sup]2[/sup] roughly Area of a head is about .2m[sup]2[/sup] Lets make it 0.4 m[sup]2[/sup]. Let’s also say that 10% conversion is what you get. 900\*.4\*.1 = 35W Not bad really. Now you’ll likely sleep or be indoors where the light levels are significantly lower than 900 w/m[sup]2[/sup] the advantage likely drops to 15 W or so. Over the course of a day that’s about 300 Cals. I hope. I hate converting units, but I like doing it more than the stuff currently composting on my desk. 🙂 ---
**Author:** ![Aeschines](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aeschines/32/16251_2.png) [@Aeschines](https://boards.straightdope.com/u/Aeschines)\ **Post date:** [October 5, 2004, 7:19pm UTC](https://boards.straightdope.com/t/technical-obstacles-in-getting-humans-to-photosynthesize/267695/4 "2004-10-05T19:19:35Z")
You could even have branches and leaves growing out of people’s heads for extra efficiency. ---
**Author:** ![dropzone](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dropzone/32/7515_2.png) [@dropzone](https://boards.straightdope.com/u/dropzone)\ **Post date:** [October 5, 2004, 7:47pm UTC](https://boards.straightdope.com/t/technical-obstacles-in-getting-humans-to-photosynthesize/267695/5 "2004-10-05T19:47:30Z")
Upside: Attractive women go around naked Downside: I go around naked. Attractive women cover up to diet. Attractive women are green, which I could get around, but… No, bad idea. ---
**Author:** ![CarnalK](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnalk/32/486_2.png) [@CarnalK](https://boards.straightdope.com/u/CarnalK)\ **Post date:** [October 6, 2004, 2:37am UTC](https://boards.straightdope.com/t/technical-obstacles-in-getting-humans-to-photosynthesize/267695/6 "2004-10-06T02:37:52Z")
Since it would mainly be useful in emergency situations maybe a lot of these problems could be solved by making just a sort of temporary bandage you can put on. A spray of some mild acid on the location to open up a little blood supply then slap it on. Of course then the main problems then would be rejection and storage but those are problems we have a better handle on so far. ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [October 6, 2004, 2:44am UTC](https://boards.straightdope.com/t/technical-obstacles-in-getting-humans-to-photosynthesize/267695/7 "2004-10-06T02:44:15Z")
Are there any lifeforms that combine plant and animal metabolisms? ---
**Author:** ![DanBlather](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@DanBlather](https://boards.straightdope.com/u/DanBlather)\ **Post date:** [October 6, 2004, 3:29am UTC](https://boards.straightdope.com/t/technical-obstacles-in-getting-humans-to-photosynthesize/267695/8 "2004-10-06T03:29:58Z")
> [@Ludovic](#): > > What other obstacles would lie ahead… It’s not easy being green. ---
**Author:** ![sleeping](https://avatars.discourse-cdn.com/v4/letter/s/839c29/32.png) [@sleeping](https://boards.straightdope.com/u/sleeping)\ **Post date:** [October 6, 2004, 5:16am UTC](https://boards.straightdope.com/t/technical-obstacles-in-getting-humans-to-photosynthesize/267695/9 "2004-10-06T05:16:43Z")
> [@BrainGlutton](#): > > Are there any lifeforms that combine plant and animal metabolisms? Sure. A euglena does. ---
**Author:** ![sleeping](https://avatars.discourse-cdn.com/v4/letter/s/839c29/32.png) [@sleeping](https://boards.straightdope.com/u/sleeping)\ **Post date:** [October 6, 2004, 5:51am UTC](https://boards.straightdope.com/t/technical-obstacles-in-getting-humans-to-photosynthesize/267695/10 "2004-10-06T05:51:58Z")
> [@](#): > > [Most species](http://www.jracademy.com/~mlechner/archive1999/euglena.html) are green because they contain chlorophyll which allows them to produce food through photosynthesis for themselves, as well as serve as primary producers for aquatic ecosystems. Some species also eat tiny particles of living matter. Euglenas use a flagellum (a whiplike appendage) that sticks out from the body, to move and are thus categorized as flagellates. > [@](#): > > **While [euglenoids](http://bio.rutgers.edu/euglena/) are typically thought of as being photosynthetic algae they are all descended from phagotrophic ancestors and a feeding apparatus can be found in virtually all euglenoid species**. In some cases this feeding apparatus is greatly reduced and consists of a pocket originating at the cell’s anterior end adjacent to the flagellar opening. The pocket is supported by interconnecting microtubules that run along its length. [photo and diagram](http://www.american.edu/cas/bio/faculty_media/zeller/gbl/euglena.jpg) ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [October 6, 2004, 6:08am UTC](https://boards.straightdope.com/t/technical-obstacles-in-getting-humans-to-photosynthesize/267695/11 "2004-10-06T06:08:07Z")
Just slapping chloroplasts into skin cells wouldn’t do you a lot of good. The enzyme that actually fixes carbon, ribulose-1,5-biphosphate carboxylase/oxygenase (RUBISCO) is composed of 8 large and 8 small subunits. The large subunits are coded for by chloroplast DNA, but the small subunits are coded by nuclear DNA. There are similar issues with Chloroplastic ATP Synthetase subunits. To get things to work, you’d have to figure out how to coordinate nuclear and chloroplastic protein synthesis. That’ll likely take a few years work.