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BobTheScientist
124558.  Thu Dec 07, 2006 3:28 am Reply with quote

Long Haired Hippy wrote:


Can this be true? I looked at it and thought that 1.4 kg can't come from 1 kg. Then I thought about the Oxygen but then I thought about the Carbon Dioxide and whether than balances out the Oxygen. Normal formula for respiration is (if my creaking mind remembers correcty)

C6H1206 + 6 O2 = 6 H20 + 6 C02



But that's burning sugar not fat. Saturated fat is to a reasonable approximation is (CH2)n which, adding Oxygen goes to CO2 and H2O. Ignoring the O2 and CO2 as gases you are converting H2C to H2O in a ratio of 14 to 18.

It's got to be more complex thatn that.

 
smiley_face
124655.  Thu Dec 07, 2006 10:26 am Reply with quote

In response to longhairedhippy (cos it's too long a post to quote)

They are storing it as fat rather than glucose. The fatty acid concerned is, if i recall, stearic acid. This has molecular formula:

C18H36O2

Therefore, for each stearic acid molecule, you can get 18 water molecules. 1kg of stearic acid is 3.5 moles, so from this you would get 63 moles of water, which weighs 1.14 kg

I apologise for having missed out the extra 1 in my original statement of the amount.

I am fairly sure that in the breaking down of the whole triglyceride molecule (glycerol plus three stearic acid molecules) there will be water obtained from other sources as well.

 
Long Haired Hippy
124673.  Thu Dec 07, 2006 11:12 am Reply with quote

BobTheScientist wrote:
Long Haired Hippy wrote:


Can this be true? I looked at it and thought that 1.4 kg can't come from 1 kg. Then I thought about the Oxygen but then I thought about the Carbon Dioxide and whether than balances out the Oxygen. Normal formula for respiration is (if my creaking mind remembers correcty)

C6H1206 + 6 O2 = 6 H20 + 6 C02



But that's burning sugar not fat. Saturated fat is to a reasonable approximation is (CH2)n which, adding Oxygen goes to CO2 and H2O. Ignoring the O2 and CO2 as gases you are converting H2C to H2O in a ratio of 14 to 18.

It's got to be more complex thatn that.


I realise that the formulae I presented was for sugar not fat. That's why I asked what was so different about fat.

I did guess that it was a lower proportion of Oxygen

Quote:
I would guess a higher ratio of Hydrogen to Oxygen such that more of the water formed comes from atmospheric Oxygen.


I did look for details of the metabolism of fat on the interweb but couldn't find a balance between the pages which gave dietary advice and the pages that went into great biochemical detail but didn't provide the molar equations I needed.

Thanks for confirming my theory. Being the nitpicker I am I hadn't thought to approximate.

However during my searches I did find some other information about camels.

Some sources say that the hump is more for storing food than water. Other agree in principle with 1 Kg of fat metabolising to more than a Kilo of water but give a ratio of 1:1.1111 instead of 1:1.4

Of far more interest though are these factoids.

Camels' red blood cells are unique amongst mammals in being oval in shape rather then circular - this helps bloodflow when dehydrated.

The blood cells are also far more stable than most and able to withstand high osmotic variation without rupturing. Handy when drinking huge amounts of water.

Their bodies can cope with a far greater temperature variation then most mammals: from 34C (93F) at night up to 41C (106F) at day. only above this threshold will they start to sweat.

Why should a desert animal be so hairy? Well their coat reflects sunlight: a shaved camel sweats 50% more to avoid overheating.

They have three set of eyelids. Two sets with lashes. These keep the sand out of their eyes. They also have sealable nostrils.

To preserve water urine comes out as a thick syrup and their feces are so dry that fires can burn off it.

 
Spinoza
144960.  Fri Feb 09, 2007 7:12 pm Reply with quote

For a definitive and not too heavy account of the physiology of the camel, try Desert Animals by Knut Schmidt-Neilsen, published about 1968.

The Royal Society of London despatched Sir Everard Home to Egypt in about 1820, to investigate camels. He cut up a few camels and discovered that nowhere in its body does the camel store water. The hump is made of fat. This led to the belief that the camel metabolises fat for energy rather than carbohydrate; it is true that fat produces more water during its oxidative breakdown than the equivalent amount of carbohydrate. Unfortunately it also requires more oxygen, which would be obtained by the camel having to breathe more. Since expired air
is a MAJOR route of water loss from the body, there would in practice be no advantage to the camel in pursuing this strategy, and it doesn't.

So why the humps? It seems that the camel stores fat in humps so it doesn't have to store it as a subcutaneous layer, where it would interfere with the camel's exchange of heat with its environment. It does allow its body temperature to rise by about seven degrees during the day, but its temperature drops during the night by the same amount. It only sweats when its temperature rises to 41 degrees, and then only in a carefully controlled way, so that for many years it was thought not to sweat at all. This animal has a variety of physiological and behavioural adaptations to allow it to survive, but they are all more sophisticated than lugging around a load of water.

It does amaze me that even today, intelligent and educated people still widely believe the myth about water in the hump. Perhaps the story about the alleged water gain from metabolising fat is more understandable, because it appears to be a more plausibly sophisticated explanation, but it is still wrong. I can only imagine that stories we are told when very young, either at school or by our parents, tend to persist in our minds long after our reason should have caused them to be expunged. Examples of this might include Father Christmas, ghosts, God........anyone got any other examples?

 
nostradamus
408958.  Wed Sep 17, 2008 2:41 pm Reply with quote

Factoid: Shillywillfollywollyrosfoshfaritation, means; 6 camels lined up in a row in the final stages of preparing to defecate simultaneously.

 
bobwilson
408960.  Wed Sep 17, 2008 2:48 pm Reply with quote

Quote:
I can only imagine that stories we are told when very young, either at school or by our parents, tend to persist in our minds long after our reason should have caused them to be expunged. Examples of this might include Father Christmas, ghosts, God........anyone got any other examples?


If you mention a notable run of luck you'll tempt fate to end it

 
PDR
408991.  Wed Sep 17, 2008 4:11 pm Reply with quote

The only true Camel hailed from Weybridge, had but one hump, indulged in synchronised spitting and excreted castor seed extracts. It was also the prefered mount of one of the classical British schoolboy heros.

What am I on about?

PDR

 
bobwilson
409071.  Wed Sep 17, 2008 9:12 pm Reply with quote

presumably billy bunter and something to do with the great camel adventure? It's far too vague in memory to be more specific than that.

 
PDR
409525.  Thu Sep 18, 2008 12:33 pm Reply with quote

bobwilson wrote:
presumably billy bunter and something to do with the great camel adventure? It's far too vague in memory to be more specific than that.


No, not even close.

By "schoolboy heros" I mean "heros of schoolboys".

The number "266" comes into it.

PDR

 
nostradamus
409626.  Thu Sep 18, 2008 2:17 pm Reply with quote

nostradamus wrote:
Factoid: Shillywillfollywollyrosfoshfaritation, means; 6 camels lined up in a row in the final stages of preparing to defecate simultaneously.

 
samivel
409758.  Thu Sep 18, 2008 7:00 pm Reply with quote

Yes, I'm sure we all read that the first time. What's the purpose of quoting it in a new post?

 
bobwilson
409767.  Thu Sep 18, 2008 7:44 pm Reply with quote

samivel wrote:
Yes, I'm sure we all read that the first time. What's the purpose of quoting it in a new post?


narcissism?

 
bobwilson
409768.  Thu Sep 18, 2008 7:46 pm Reply with quote

is it biggles?

 
PDR
409796.  Fri Sep 19, 2008 2:45 am Reply with quote

bobwilson wrote:
is it biggles?


That's the chap, so the "Camel" in question is obviously the Sopwith 2F1.

PDR

 
nostradamus
409808.  Fri Sep 19, 2008 3:13 am Reply with quote

bobwilson wrote:
samivel wrote:
Yes, I'm sure we all read that the first time. What's the purpose of quoting it in a new post?


narcissism?


yes.

 

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