I believe that the key is: one molecule of glucose gives 36 ATP molecules through cell respiration.
Sucrose has one glucose and one fructose -which can be isomerized into glucose, hence equals two glucoses.
Thus:
(2000 Kcal/day ) / ( 4 Kcal/g) = 500 g of sucrose fullfil dayly energy intake

500 g/day x Avogadro constant = 3,01×10^24 sucrose molecules.

That is double, aprox = 6×10^24 molecules of clucose

Finally multiply by 36: 216×10^24.

More neatly: 2,16×10^22 molecules of ATP

Hope this helps.

You forgot the molecular weight

Dr. Featherstone’s class can be pretty challenging…

This is what I got:

Sucrose consists of Glucose and Fructose. Both of which can enter glycolysis (fructose can be synthesized as an intermediate in the glycolysis process). So each round of glycolysis, one molecule of glucose produces a net gain of 2 ATP. The krebs cycle produces 2 more ATP, and the electron transfer chain produces an additional 32 ATP. A total of 36 ATP is produced essentially from 2 pyruvate molecules or 1 glucose molecule. Since sucrose contains two molecules that can enter the cellular respiration process (36 ATP x 2 Molecules = 72 ATP per Sucrose)

2,000 KCal for our diet / 4 KCal in a gram of sucrose = 500g of sucrose.
500g sucrose / 342.3g molecular weight of sucrose = 1.4607 moles of sucrose.
1.4607 moles of sucrose x 6.02 x 10^23 = 8.793 x 10^23 molecules of sucrose.
8.793 x 10^23 molecules of sucrose x 72 ATP per molecule of sucrose = 6.33 x 10^25 ATP produced.

However, this is assuming that all we eat throughout the day is 2,000 KCal or 500g of pure sucrose (table sugar). If you read the last sentence of the first paragraph it says "Dietary fats (usually 18 to 20 carbons) contain approximately 9 dietary calories per gram." I’m assuming we have to take this into consideration too? I haven’t gotten that far yet in the book to understand how much ATP dietary fat produces.

All this could be wrong, I don’t know, keep this thread going.

I’m pretty sure that we need to include the dietary fats (or he is just trying to trick us).
I have these notes from his lecture:
– The R-chain in fatty acyl CoA has 16-20 carbons
– Carbons from fatty acids go to citric acid cycle
– 8 fatty acid cycles per 2 citric acid cycles (this is for 16 carbons, so for 18 carbons it should be 9 fatty acid cycles)
– 2 carbons are lost in each fatty acid cycle
If you have the 2nd edition of the book, look at pages 438 and 439. Under figure 13-9 it says "each turn of the cycle shortens fatty acid chain by two carbons and generates one molecule of acetyl CoA and one molecule each of NADH and FAGH2." I haven’t found how many ATP are produced.
I have found this thread: about8393.html?hilit=Palmitic
They explain how to calculate how much ATP would be produced if there are 16 carbons so I think we just need to calculate this for 18 carbons. I still have no idea how to incorporate those 9 dietary calories per gram.

OK, let me try to calculate this.

18 carbon/2 carbons= 9 acetyl CoA
1 FADH2 produced = 2 ATP
1 NADH produced = 3 ATP
TOTAL: 5 ATP per 1 fatty acid cycle
"The last step produces 2 acetyl-CoA and thus oxidation of C16 takes place in 7 steps, not 8." So for 18 carbon it would be 8 steps
ATP from fatty acid cycle = 8 steps and 5 per turn = 40 ATP
There are 12 ATP produced from each acetyl CoA in the citric acid cycle (1 ATP, 3 NADH (so 3*3)= 9 ATP, 1 FADH2 (so 2)= 2 ATP)
9 acetyl CoA * 12 ATP = 108 ATP
108+40= 148 ATP but since 2 ATP are needed to start the cycle, it is 146 ATP

I’ve looked at other websites and it pretty much always says that if there are 18 carbons then 146 ATP are produced from fatty acid cycle.
If you know how to go from there then please post it. I need help too.
PS- Go through these calculation carefully because it helped me understand that printout he posted on Blackboard and I’m pretty sure he will ask this on the exam.

So I think we have to go back to the very beginning since when you calculate >>2,000 KCal for our diet / 4 KCal in a gram of sucrose = 500g of sucrose<< that is only for sucrose and we need to make room for the dietary fats. Biochem would help answering this question lol.

We can’t do
2,000 KCal for our diet / 4 KCal in a gram of sucrose = 500g of sucrose AND
2,000 KCal for our diet / 9 KCal in a gram of dietary fats = 222 g of dietary fats
because that’s calculating 2 different things.

And now I’m stuck.

So, as noted above:

Provided that one lives sweetely and only on sucrose. Let’s see what happens when living on oil:

2,000 KCal for our diet / 9 KCal in a gram of fats = 222,2g of fat.
Molecular wheight of a saturated C18 fatty acid -stearic (02C18H36) is 16×2+12×18+36= 284 (if am not wrong)
222 g of fat / 284g molecular weight = 0.782 moles of stearic acid.
0.782 moles of stearic x 6.02 x 10^23 = 4.708 x 10^23 molecules of stearic.
Now, since

4.708 x 10^23 molecules of stearic x 146 ATP per molecule of stearic = 6.874 x 10^25 ATP produced
whic is pretty much tha same than on sugar!

Figures can be sommehow if we speak of moles instead of molecules.

Hence, my conclusion is: every day, the average person uses nearly 650 moles of ATP .

Please check.

I think you cannot answer this question in the way it’s given. Simply you don’t know, how much sugar and fats such a person consumes.

What about to get it the other way? Person need 2000 calories. ATP produces about 30 kJ/mol (?) -) calculate this into calories, divide and you’re done. It will be just highly rough estimation, but with "There are a little less than 4 dietary calories " and "contain approximately 8 dietary calories" you cannot do much better.

You need 2000 Kcal a day irrespective whether they come from.
Our calculations show that the ammount of ATP involved would be very similar on a diet based only on sugars and on a diet based only on fat. Hence diet composition is irrelevant.

I encourage you to calculate the other way round, as you have cleverly suggested, and check if this guives a similar result.

Cheers

Yep, that’s the point, if you know how many calories you need and from that you calculate amount of consumed sugar or fat, you will always have the same amount of ATP.

All well except for the begining.

Average metabolic waste is 2000 KCal, not 2000 Cal.

Sometimes dietists speak of calories meaning Kcal, just for briefing.

That’s all.

It does require quite a bit of energy to break the alpha 1,4 glycosidic bond of glucose and fructose. Shouldn’t that be taken into account?

Really? How much is it?

Well, some glycoside hydrolase would break the bond – It would probably couple ATP hydrolysis or NADH/FADH hydrolyis and use a positive magnesium ion catalyst. I’d have to find out more info and do a Gibbs on that one. I have no idea regarding the exact energy consumption. Does anyone else?