Wikipedia:Reference desk/Archives/Science/2017 June 12

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June 12

Why does water not have calories?

I'm trying to understand why water doesn't have calories and we can drink as much as we want without to be afraid of obesity. Would it be true if I'll say that just fats, carbs or proteins can have calories and all the rest substances don't hvae? 93.126.88.30 (talk) 01:00, 12 June 2017 (UTC)

Add alcohol to the list of things we consume with calories. Digestion produces energy by a type of slow combustion, so only substances which are flammable (once the water is removed) give us energy. Of course, we can't digest all flammable substances, so don't drink diesel fuel. StuRat (talk) 01:05, 12 June 2017 (UTC)

The calorie is a unit of energy. This energy is produced by oxidation (what StuRat calls "a type of slow combustion"). Since water cannot be oxidized (at least, not in this context), it has no calories. Shock Brigade Harvester Boris (talk) 01:13, 12 June 2017 (UTC)

And cold water has negative calories. But there are many things we consume that aren't energy producing but are catalysts for converting organic matter into storable energy. Vitamins and minerals come to mind. --DHeyward (talk) 04:54, 12 June 2017 (UTC)

And we even have a Negative-calorie food article. DMacks (talk) 05:00, 12 June 2017 (UTC)

Which turns out to be fictitious; bad news for dieters. -- Jack of Oz ^{[pleasantries]} 05:03, 12 June 2017 (UTC)

It is true that all chemicals potentially react, and water could react with something to produce energy. But the Earth is covered in water and those things it reacts with are few. Even if there were a deposit of native potassium someplace and some kind of bacteria were somehow degrading it for energy (very carefully) we'd call them chemotrophs and attribute the calories, arbitrarily, to the potassium. (Actually I don't know if anything can exploit energy from a halocline, which is less dramatic, but would be attributed to the salt) But if you had an alien planet made out of solid sodium or something, then quite possibly their product labels would detail the calories in the added water. Wnt (talk) 10:03, 12 June 2017 (UTC)

• Alcohol was already mentioned, and there are other chemicals that can be metabolized to produce energy as well, for example acetone and acetic acid (i.e., vinegar). Looie496 (talk) 14:24, 12 June 2017 (UTC)

Ugh! I do not like the idea of drinking acetone, thanks! I'll stick to using it to clean my nails. Yes, it does make you somewhat "high", I hear. But the only people I've ever found drinking the stuff plain, were the sort who ended up in a psych ward, and were desperate to use anything to escape reality. (Yes, among psych patients, drinking nail polish remover is not unheard of. In old times, nail polish remover often included gamma-Butyrolactone, which was something of a recipe for abuse). Eliyohub (talk) 15:27, 12 June 2017 (UTC)

What's meant by casual sexual encounters in this study?

Do they only mean one time sexual encounters with strangers,or does casual sexual encounters also include sex in regular casual sexual relationships?Uncle dan is home (talk) 20:50, 12 June 2017 (UTC) See here:http://www.telegraph.co.uk/science/2017/01/19/one-night-stands-women-regret-men-regret-not-having-evolution/

The paper referred to is at http://journals.sagepub.com/doi/pdf/10.1177/1474704916682903 and it doesn't seem to define "casual sex", leaving it up to the survey's respondents to decide what it means. Since the research was done in Norway I expect a Norwegian expression was used. "One night stand" used in the Telegraph does not seem to be used in the paper. Thincat (talk) 22:25, 12 June 2017 (UTC)

Shared genes between siblings

As a male, am I closer genetically to my brother than to my sister? --Clipname (talk) 23:00, 12 June 2017 (UTC)

• Yes, most likely. He and you share the same Y chromosome and the same mitochondria. But see meiosis. Chromosome segregation is random. μηδείς (talk) 00:52, 13 June 2017 (UTC)

• Full brothers and sisters also share the shame mitochondria, and hence mitochondrial DNA, as they come from the mother. StuRat (talk) 02:02, 13 June 2017 (UTC)

• As for the chances, that's only 1 of 46 chromosomes you know you share with your brother, so you could easily have more of the other 45 in common with your sister. So, the chances are somewhat above 50% that you share more genetic material with your brother, but not that much above. Can somebody do the math ? StuRat (talk) 02:04, 13 June 2017 (UTC)

Different chromosomes are not equal in size, and the Y chromosome is the one of smallest. (See the table at Chromosome#Human chromosomes.) If the question is "how much genetic material is in common", you can't just count all of them equally. --76.71.5.114 (talk) 05:58, 13 June 2017 (UTC)

It is perfectly possible that you share more alleles with your sister than your brother. Without analysis of you as individuals, all we can do is speak of averages. In that case, medeis is correct, and on average we would expect a slightly higher number of shared alleles due to the Non-combining region of Y Here [1] is a nice article with citations to the scientific literature. It explains how the chromosomal lengths differ, and talks a bit about sibling relatedness as it pertains to sex. See also coefficient of relationship, consanguinity, and genetic distance. SemanticMantis (talk) 14:32, 13 June 2017 (UTC)