ATP outputs in aerobic respiration

[Stick]

Nature of Biology doesn't explain the link reaction between glycolysis and the Krebs cycle so now I'm a bit confused. Just to confirm, are two ATP molecules synthesised per glucose molecule in glycolysis and 34 in the electron transport chain? I'm trying to figure out where the two ATP molecules that are used to transport pyruvate into the mitochondria come from.

[Yacoubb]

Glyolysis - net output of 2 ATP molecules/glucose molecule
Kreb's Cycle - production of 2 ATP molecules/glucose molecule
Electron Transport Chain - (32-34) ATP molecules/glucose molecule.

That 32-34 is purely explained by the fact that some cells like heart cells, liver cells or kidney cells produce 38 ATP molecules/glucose molecule during aerobic cellular respiration, purely because their specialised functions require large amounts of ATP for effective functioning. Most somatic cells required only 36 ATP molecules/glucose molecule.

2 + 2 + 32 = 36 ATP molecules/glucose molecule
2 + 2 + 34 = 38 ATP molecules/glucose molecule

Glucose is broken down into 2 pyruvate molecules, and we know that any catabolism (breakdown of a compound into smaller units - or in this case pyruvate), releases energy and is exergonic, in the form of a net output of 2 ATP molecules/glucose molecule broken down. I am pretty sure this is right, maybe someone may like to clarify, or perhaps ammend a few elements of my response.

[alondouek]

From one glucose molecule

Glycolysis = net 6 units formed (technically 4, but 2 of those are used up in the glycolysis preparatory phase)

• 4 from substrate-level phosphorylation
• 4 from oxidative phosphorylation
• BUT 2 lost from the glycolysis prep. phase

Oxidative phosphorylation (decarboxylation) of pyruvate = 5 units

Kreb's cycle = collectively, 20 units formed

Hence, total yield from one glucose molecule is 31 units of ATP (however, there is a theoretical yield of 38, but this does not occur due to energy requirements in performing some functions that I can't remember).

[ealam2]

Yacoubb it's exergonic not exogonic.
Anyways, what is pyruvate molecule?

[Yacoubb]

Yacoubb it's exergonic not exogonic.
Anyways, what is pyruvate molecule?

Woopsie Thanks for that, I actually forgot what it was and I still wasn't satisfied when I typed that out. Too much Chemistry and exothermic reactions LOL!

[alondouek]

Yacoubb it's exergonic not exogonic.
Anyways, what is pyruvate molecule?

Pyruvate is the output of glycolysis. It is decarboxylised to Acetyl-CoA (Acetyl Coenzyme A), which you might recognise.

[Stick]

Glyolysis - net output of 2 ATP molecules/glucose molecule
Kreb's Cycle - production of 2 ATP molecules/glucose molecule
Electron Transport Chain - (32-34) ATP molecules/glucose molecule.

That 32-34 is purely explained by the fact that some cells like heart cells, liver cells or kidney cells produce 38 ATP molecules/glucose molecule during aerobic cellular respiration, purely because their specialised functions require large amounts of ATP for effective functioning. Most somatic cells required only 36 ATP molecules/glucose molecule.

2 + 2 + 32 = 36 ATP molecules/glucose molecule
2 + 2 + 34 = 38 ATP molecules/glucose molecule

Glucose is broken down into 2 pyruvate molecules, and we know that any catabolism (breakdown of a compound into smaller units - or in this case pyruvate), releases energy and is exergonic, in the form of a net output of 2 ATP molecules/glucose molecule broken down. I am pretty sure this is right, maybe someone may like to clarify, or perhaps ammend a few elements of my response.

This is what Nature of Biology says, but as I said above, it does not explain the linking reaction between glycolysis and Krebs cycle very well (in fact, it says it's actually part of the Krebs cycle). The textbook also doesn't stipulate that in most eukaryotic cells, two ATP molecules are used to transport the pyruvate molecules into the mitochondria. Basically, the gross output of ATP molecules needs to be 38 whilst the net output may be 36, so I'm trying to work out in which stage are the two 'excess' ATP molecules formed (it's either that glycolysis produces four ATP molecules or that electron transport chain produces 34, but I'm not sure which one it is).

[alondouek]

This is what Nature of Biology says, but as I said above, it does not explain the linking reaction between glycolysis and Krebs cycle very well (in fact, it says it's actually part of the Krebs cycle). The textbook also doesn't stipulate that in most eukaryotic cells, two ATP molecules are used to transport the pyruvate molecules into the mitochondria. Basically, the gross output of ATP molecules needs to be 38 whilst the net output may be 36, so I'm trying to work out in which stage are the two 'excess' ATP molecules formed (it's either that glycolysis produces four ATP molecules or that electron transport chain produces 34, but I'm not sure which one it is).

I'll briefly reiterate; 38 units is only a theoretical figure - some of the ATP produced is consumed throughout the three main stages of respiration. A net production of 31 units is the most recent correct figure I've seen.

[Bad Student]

That 32-34 is purely explained by the fact that some cells like heart cells, liver cells or kidney cells produce 38 ATP molecules/glucose molecule during aerobic cellular respiration, purely because their specialised functions require large amounts of ATP for effective functioning. Most somatic cells required only 36 ATP molecules/glucose molecule.

Do you know how the heart, liver and kidney cells produce the extra two ATP?

From one glucose molecule

Glycolysis = net 6 units formed (technically 4, but 2 of those are used up in the glycolysis preparatory phase)

• 4 from substrate-level phosphorylation
• 4 from oxidative phosphorylation
• BUT 2 lost from the glycolysis prep. phase

Oxidative phosphorylation (decarboxylation) of pyruvate = 5 units

Kreb's cycle = collectively, 20 units formed

Hence, total yield from one glucose molecule is 31 units of ATP (however, there is a theoretical yield of 38, but this does not occur due to energy requirements in performing some functions that I can't remember).

Is this stuff university level or vce biology level?

Nature of Biology doesn't explain the link reaction between glycolysis and the Krebs cycle so now I'm a bit confused. Just to confirm, are two ATP molecules synthesised per glucose molecule in glycolysis and 34 in the electron transport chain? I'm trying to figure out where the two ATP molecules that are used to transport pyruvate into the mitochondria come from.

I think Biozone mentions the link reaction.

[alondouek]

Is this stuff university level or vce biology level?

Could be uni stuff, but it was taught to me in 3/4 Biol.

[Yacoubb]

Do you know how the heart, liver and kidney cells produce the extra two ATP?

I presume that it is because heart cells and kidney cells specialised for functions that require high ATP energy amounts to execute roles would have more mitochondria? I'm sure there is definitely a more complex explanation to this.

[pi]

Is this stuff university level or vce biology level?

Uni for sure.

[Bad Student]

Could be uni stuff, but it was taught to me in 3/4 Biol.

What Yacoubb posted is what I'm being taught at school.

On a side note, everyone here seems to know aerobic respiration in much more detail than I do. My teacher at school glossed over aerobic respiration in one lesson. He kept saying that we didn't need to know it in this much detail.

[alondouek]

What Yacoubb posted is what I'm being taught at school.

On a side note, everyone here seems to know aerobic respiration in much more detail than I do. My teacher at school glossed over aerobic respiration in one lesson. He kept saying that we didn't need to know it in this much detail.

In that case, I would recommend you approach your teacher about some more coverage of respiration in class or one-on-one if you (or your class) are not confident on the topic.

I don't know about the new study design, but it was a pretty important concept last year (though maybe not to the extent I was taught - but hey, a bit of extra knowledge is never a bad thing to have )

[Yacoubb]

You have to know the following about Aerobic Respiration:

That Aerobic Cellular Respiration is made up of three stages:
(1) Glycolysis that takes place in the cytosol
(2) Kreb's Citric Acid Cycle that takes place in the matrix of the mitochondrion.
(3) Electron Transport Chain that takes place in the cristae of the mitochondrion.

You need to know the amount of ATP molecules produced per stageL
(1) Glycolysis - net output of 2 ATP molecules/glucose molecule
(2) Kreb's Cycle - production of 2 ATP molecules/glucose molecule
(3) Electron Transport Chain - production of 32-34 ATP molecules/glucose molecule.

You need to know the inputs and outputs of the overall reaction:
Inputs:
- Glucose
- Oxygen
with the help of enzymes
Outputs:
- Carbon Dioxide
- Water
- 36 to 38 ATP molecules.

Learn the ATP synthesis from ADP

ADP + Pi ----> ATP + H₂O
Remember, this is the condensation reaction where a water molecule is released; this is why the bond between the second and third inorganic Phosphate is so energy-rich, and what makes Adenosine Tri-phosphate such an efficient source of energy for any endergonic biochemical process that occurs within living organisms to sustain life.

Learn what happens at each stage, and also learn the chemical reactions that take place in each stage. A flowchart really helps here; note: if you do a flowchart, use generalised headings, and then write up an attached report that outlines what is happening at each particular time.

E.g. Glucose to Pyruvate - Glycolysis
* Glyco = sugar
* Lysis  = bursting
~ bursting sugar; the breakdown of glucose into pyruvate causes an exergonic reaction where there is a net output of 2 ATP molecules for every glucose molecule broken down.
~ this takes place in the cell cytosol.
~ ATP guides the pyruvate to mitochondria when Oxygen is present.
~ No oxygen - the pyruvate will accumulate in muscle tissue as lactic acid, and result in muscle fatigue.

I personally find this extremely helpful in understanding the processes