Respiration

[SleepyTomato]

Something funny I found with chemical equation for respiration:

C6 H12 O6 (glucose, 180.18 g/mol) + 6 O2 (oxygen gas, 32 g/mol) -> 6 CO2 (carbon dioxide, 44.01 g/mol) + 6 H2O(water, 18.02 g/mol)

Assuming that the amount of CO2 left in the human body is negligible, one mole of reactions results in a net loss of 72.06 grams of mass (180.18 from glucose - 6 * 18.02 from water = 72.06).

This means a person loses mass when he/she breathes. Why don't we notice this? Do other processes make up for this or is this too insignificant to really affect our weight?

 

[Mark R]

Well, there's a difference between cellular respiration (which is what you are describing there) and ventilation (which is what your lungs do).

Breathing is to keep the concentration of oxygen and CO2 in the body stable.

Cellular respiration is what turns calories (from food) into energy for life. However, as energy stores in the body are consumed, this does cause loss of weight. So, if you eat less food than your body uses then you lose weight (as energy stores are consumed by respiration).

A typical adult will have about 1 lb of carbohydrate stored in their body. If you don't eat for a day, then this will be consumed by the above reaction yielding about 1500 kcal - and you will lose weight (about 1 lb).

In practice, most energy stores in the body are fat - you need to use up 3000 kcal of energy to lose 1 lb of fat.

 

[Peter]

You'll actually need to expel about 5000 to 6000 kcal to lose 1 pound of fat, although that pound of fat is only "worth" 3000 - simply because the human body primarily is a carbohydrate burner, using fat only as a supplemental source. Even perfectly trained endurance athletes hardly get over 60% fat burning ratio.

 

[Genx87]

Remember when I was still playing doing winter workouts for football in the morning, 6:15-8:00, coming back at 10:00 for Swimming 101, 45 mins in the pool, then track practice from 3:30-5:00.

Oh those were the days, I could eat about 8000+ calories a day and still lose body fat lol

 

[BrownTown]

basically the answer to the origional question is that the weight changes are gonna be way to small to notice, but certainly you will lose weight if you continue to burn calories and do not eat more. You will also eventually die .

 

[SleepyTomato]

If I understand correctly, the net loss of six carbon atoms per reaction is the mechanism by which people lose weight through exercise. If not, then how does the mass lost through exercise leave the body? Does anyone know how significant the burning of other sugars (sucrose, fructose, etc) in the body is?

 

[Rockinacoustic]

You forgot a key part of your respiration equation, there's no energy in it!. And energy is not weightless. I don't know the mathematical chemistry of it, but I have the Biology of it down pat.

Aerobic Respiration isn't just one simple reaction, it's actually broken down into 4 steps:

1.Glycolysis: Basically this is the process where the glucose (sugar) is split. Glucose splits into pyruvic acid
2.Acetyl CoA: Pyruvic acid and Oxygen is converted to Acetyl Co-enzyme A. This releases excess Carbon in the form of Carbon Dioxide (CO2).
3.Krebs Cycle: The Acetyl CoA is sent through the mitochondrial matrix(don't mind the use of big words). Here it combines with oxaloacetate to form citric acid. Not only this but it produces elements that carry excess hydrogen atoms
4.Oxadative Phospohoralation: This is where 8/9th's of the Energy is produced. Those elements that carry excess hydrogen also carry excess electrons. The electrons are transfered to oxygen, resulting in the formation of energy. This is produced by what is called an Electron Transport Chain. Basically oxygen is the final acceptor of electrons to form water. This is why it's called "aerobic" respiration.

Now what is this energy that is produced? It is called ATP or Adenosine Tri-Phosphate (one molecule of adenosine, bonded to three phosphates). Aerobic respiration both produces and uses ATP in each of the four steps. The net result is 36 ATP, so:

C6 H12 O6 + 6 O2 -> 6 CO2 + 6 H2O + Energy (36 ATP)

I dare not revisit my years of chemistry, but the end result of Respiration looks awfully heavier now.


If there's any bio people or majors here, please feel free to correct me if i'm wrong. I have yet to start my freshman year of college, so be nice

 

[BrownTown]

Well, obviously the reaction in the body isn't the combustion reaction shown above, the reaction is coupled with the ADP + Phosphate -> ATP reaction in order to provide the energy is a form the body can use. The complete chain of events is of course very complicated, but the reaction he showed more or less represents what is happening.

here is a simplified version of the energy production pathways
http://healthbuilding.com/Metabolism_GIF.gif

There are also pathways for the creation of everything else you need as seen here:
http://www.ideacenter.org/stuff/content...51ce84dfdb8209/misc/metabolism_big.jpg

 

[Rockinacoustic]

here is a simplified version of the energy production pathways
http://healthbuilding.com/Metabolism_GIF.gif

Yup, that's basically the flow of what i wrote. It is a very complicated process. I think there's too many variables in the human body to get a sure answer to the OP's question.

 

[BrownTown]

well, all the intermediates involved mroe or less only catalize the actual reaction seeing as they are not consumed in the reaction, onle serve as intermediates. What matters is the fact that the production of CO2 by the body is larger in mass than the consumption of O2, and so mass is lost via respiration. However, its only a few grams a breath. You would be alot more likely to "feel" a weight difference after taking a large dump than by breathing alot. Also, the body goes threw a lot of water in a day and the vast majority is not produced by this reaction but is drank, and then excreted as urine and sweat. In fact when you burn alot of calories most of the weight loss is associated with losing water which is associated with the sugar, and not actually using up the sugar itself. But as was stated before, your sugar reserves are not very large compared to fat reserves, so if you actualyl want to lose weight it is by metabolizing fat, nto sugar.

 

[CycloWizard]

Like others have hinted, the reason you don't notice this mass loss is because it happens very gradually. Assuming all carbs, 72 g is about 290 calories. Jogging on a treadmill for 15 minutes or so might burn this many calories (very approximate ). Since 72 g is about 0.16 pounds, this equates to 0.01 pounds lost per minute, or 0.17 ounces per minute, a rate much lower than you would ever notice even with a pretty good scale.

 

[DrPizza]

When you exercise and burn calories, and lose weight, the weight doesn't magically just disappear. You're right - it's exhaled in the form of carbon dioxide; just too gradually to notice.

 

[Peter]

Originally posted by: BrownTownso if you actualyl want to lose weight it is by metabolizing fat, nto sugar.

However (and this is a point thoroughly missed by "popular" diets), the human body cannot and does not metabolize fat without sugar - it chemically doesn't work, and even while it does, the fat metabolism is way too slow and way too weak to supply the body's entire energy needs. Anyone who's doing endurance sports knows the steep power loss at the moment your blood sugar is dropping for lack of carbs.

Also, the brain cannot use fat at all, it's sugar-only.

 

[Peter]

Originally posted by: CycloWizard
290 calories. Jogging on a treadmill for 15 minutes or so might burn this many calories (very approximate ).

Make it 30 minutes of medium speed running, and you'll be about right for a normal weight adult male.
This is the 2nd most favorite mistake in weight loss attempts ... grossly overestimating the energy output in sports.

 

[CSMR]

Originally posted by: SleepyTomatoThis means a person loses mass when he/she breathes. Why don't we notice this? Do other processes make up for this

how about eating

 

[SleepyTomato]

Biology was too long ago for me to remember, but that stuff sounds familiar. Does anyone have any percentages for the burning of other sugars? Since I've never seen other sugars mentioned in chemical equations regarding respiration, I'm not even sure if it happens.

 

[Peter]

Digestion breaks all carbohydrates down into simple sugar before sending the stuff off to the muscle or brain tissue.

 

[CycloWizard]

Originally posted by: Peter
Make it 30 minutes of medium speed running, and you'll be about right for a normal weight adult male.
This is the 2nd most favorite mistake in weight loss attempts ... grossly overestimating the energy output in sports.

Yeah... I forget that I'm a big, tall, goofy bastard. Those numbers are about right for me, but I'm much larger than the average bear. Just divide the rates I said by two to get an idea then.

 

[theMan]

do you feel lighter when you crap? after a game of basketball, when you lose pounds of water? no. the body is retarded.

 

[Sc4freak]

Originally posted by: theman
do you feel lighter when you crap?

Actually, yes.

 

[Steve]

Originally posted by: theman
do you feel lighter when you crap?

I know I do!

 

[Born2bwire]

Originally posted by: sm8000

Originally posted by: theman
do you feel lighter when you crap?

I know I do!

[RonWhite]Ever take a crap so big that your pants fit better?[/RonWhite]

 

[DrPizza]

Originally posted by: DrPizza
When you exercise and burn calories, and lose weight, the weight doesn't magically just disappear. You're right - it's exhaled in the form of carbon dioxide; just too gradually to notice.

Returning this topic back to "highly technical" (and away from the toilet), I suppose we could add that during chemical processes when energy is released, that energy comes from mass (E=mc^2). So, through the processes of radiation, convection, and conduction, heat is removed from your body. In the process, you've lost the mass that produced that heat.

E=mc^2 applies just as much to chemical reactions as it does to nuclear reactions. But, don't take this too far... if you burn 2000 calories a day, (and, if I'm not mistaken, food Calories are actually kilocalories, someone correct me if I'm wrong)

Also, cool thing you can do with google: example

2.4x10^11 joules
2.7x10^-6 kilograms of mass is converted to energy in your lifetime...

(math error possible, I didn't double check)

 

[SuperFungus]

[/quote](and, if I'm not mistaken, food Calories are actually kilocalories, someone correct me if I'm wrong)
[/quote]

yea your correct, I'm pretty shure that they use a capitol C to denote that on the lables. Even if the capitol C thing is wrong I know that all the japanese stuff I've come across is marked in Kca and that stuff is definately not a thousand times more chaloric than american food