# How much energy would a hypothetical organism require to regenerate mild to semi-moderate trauma via pluripotent stem cells?

So, we have this heavily-altered human that can regenerate from stem cells. Let's say that they suffer a "flesh wound" - in this case, let's say an ugly stab wound through the hand with a pencil that severs several tendons, chips bones, and tears muscle groups, but does not damage any complex organs (it's the hand, after all, not the chest cavity).

How much energy would be required for a network of pluripotent stem cells to regenerate the tissues damaged in this wound? Never mind the time; some biological mechanism can be worked out to spread it over the course of a week or such so that they're not starving constantly as their body pours everything into repairing it.

Energy is energy, no matter what.

Take the composition of the part you want to regenerate, do some math by taking into account the caloric supply of each part, and you know how much energy is needed.

Example: you want to rebuild a part which is made by 100 grams of fat, 200 grams of muscles, 50 grams of bones. Look up in a table how much energy each of them supply per unit weight, multiple by the weight and add all up. The energy you get from them is the energy you will need to put into making them, apart some yield related loss.

• In this case it's a stab wound, so he hasn't actually lost any tissue that has to be grown from scratch. Also, if he does grow tissue, it's going to require a lot more than just the Calories. Children put on about 5-10 lb per year (depending on age). If it was all fat (the most Calorie-dense tissue) those 10 lbs would be only 96 additional Calories per day. But if you look at the Calories-per-kilogram children need, it can be in the area of 1000 more per day than an adult of the same size. Growing most kinds of tissue costs a lot more than just the Calories in the tissue. Commented Jul 25, 2021 at 7:44

Precise information might not be available, but from here:

So, while a normal person may need only 25-30 kcals per kilogram per day, a person with moderate illness or injury needs 30-35 kcals/kg, and a person with critical injury or illness needs 35-40 kcals/kg.

From here:

Energy expenditure increases depending on the severity of the injury: long bone fractures, for example, may increase your basal metabolic rate1 by 15-20%.2 If your basal metabolic rate is 2,000 calories a day, that’s an extra 300-400 calories, though minus the amount you may no longer need because of exercise.

We might suppose that the injury you described is like a long bone fracture. If a long bone fracture takes 300 extra Calories per day, and takes 6 weeks to heal, that's 12600 Calories.

• Probably kCal not calories? 1 calorie is about 4.2J Commented Jul 26, 2021 at 5:18
• @MolbOrg "calorie" refers to to two different units, one a thousand times greater than the other. en.wikipedia.org/wiki/Calorie In a dietary context, Calorie means the same as kcal, especially when written with a capital C. Commented Jul 26, 2021 at 6:19
• I know, "In the United States, most nutritionists prefer the unit kilocalorie to the unit kilojoules, whereas most physiologists prefer to use kilojoules. In the majority of other countries, nutritionists prefer the kilojoule to the kilocalorie." - as for international place may make sense to stick to majority, but atm comments under the answer clarify things enough which units did u use. Freedom units forever, lol. On the other hand I missed to notice that your cites are in proper units, okay it was just mixture of those, never mind Commented Jul 26, 2021 at 7:02