Mitochondrial energy pathways

[SWEngineer]

When we say "mitochondrial energy pathways", is that the same as "cellular respiration pathways"?

Thanks.

[daniel.kurz]

Yes.

[angel92]

yeah rite

[SWEngineer]

I asked my tutor about this, and seems that it is different, and understood that mitochondrial energy pathways are what occur in the mitochondria. That is Krebs cycle and oxidative phosphorylation, excluding glycolisis that occurs in the cytoplasm.

[daniel.kurz]

I asked my tutor about this, and seems that it is different, and understood that mitochondrial energy pathways are what occur in the mitochondria. That is Krebs cycle and oxidative phosphorylation, excluding glycolisis that occurs in the cytoplasm.

What you tutor told you was incorrect. Cellular respiration refers to the oxidation of a substrate with the end goal of high energy products that can provide "energy" to do work in the cell. Whether the generation product is ATP, GTP, UTP, or something else, does not matter the cellular respiration goes in the same direction. The factor that has to be clarified is the outside electron acceptor necessary when talking about respiration. In cells, cellular respiration refers to the ultimate oxidation and resultant reduction of some final electron acceptor. Most people know this to refer to oxygen as in the case of aerobic respiration which talks about oxygen usage (we humans do this and thus oxygen is necessary for life). There is also anaerobic respiration as in the case with some microbes that can use an alternate electron acceptor such as iron, arsenic, etc etc. These cells do not use oxygen.

Glycolysis refers to an energy production pathway, but it is not a cellular respiration pathway. It is strictly a catabolic "anaerobic" (meaning without oxygen required) step. It does involve oxidation and reduction like any biochemical pathway, but that does not mean cellular respiration.

I hope that cleared things up.

[JackBean]

are you sure that glycolysis is not part of cellular respiration?
http://en.wikipedia.org/wiki/Cellular_r ... Glycolysis
http://biology.about.com/od/cellularpro ... ration.htm
http://tinyurl.com/cellular-respiration-pictures

[daniel.kurz]

The About article is quite wrong and wikipedia article doesn't say anything about glycolysis as part of respiration. Look at the credentials of the writer of that article. The image link is the only one that is valid. I've attached a picture to show my point. The one caveat that I should mention is that in prokaryotes cellular respiration occurs in the cytoplasm. We are not talking about prokaryotes because they don't have mitochondria.

[JackBean]

what's wrong with the about article? Since Wiki mentiones glycolysis in article Cellular respiration, I would assume, that glycolysis is part of cellular respiration in accordance to Wiki. Also look on the bottom of the page, where they sort different metabolic pathways, there is the glycolysis mentioned as part of cellular respiration as well

[daniel.kurz]

Unfortunately, both are wrong. Its a very common mistake but there is nothing about cellular respiration involved in glycolysis. Cellular respiration only refers to the action of oxidizing carbon compounds to its most oxidizable state and reducing some final acceptor.

Glycolysis uses substrate level phosphorylation to make ATP from some biomass and does not require oxidative phosphorylation which is the ultimate breakdown.

To be fair, glycolysis is required for cellular respiration but glycolysis doesn't is not incorporated within glycolysis. The reasoning being that in the case of cells like yeast they can undergo both cellular respiration and cellular fermentation. Both require glycolysis and so there must be a distinction between the two by stating that glycolysis is outside of either.

I've had this same debate with my past professors and they convinced me of my current view. They are the experts in cellular metabolics.

[Maatomaat]

Glycolysis is a stage of cellular respiration.
I attached this image that is a page of "Campbell Biology book" to prove it:
http://uploadkon.ir/uploads/479b3759080 ... 5ce24a.jpg