eh, anyone got any acronyms for glycolysis or krebs cycle :\

TCA = tricarboxylic acid cycle = krebs

Thanks for bringing this up because we've come a long ways since my college biology. You made me do some research.

krebs cycle

I read further that the longer your krebs cycle cranks with some vigor,so do you into old age. Krebs, don't fail me now.

Just aman

Well if you really want some detail...

 

Pyruvate is converted to pryuvate dehydrogenase by HS-CoA, and the free hydogen is used convert NAD+ to NADH, and also produces CO2. Then PyrDH is converted to Acetyl CoA, and then to citrate synthase by way of oxaloacetate, which has a free energy change of -7.5kJ/mol. Then citrate is formed and converted to isocitrate by way of aconitase, which a free evergy change of +1.5. The isocitrate loses a hydrogen to convert another NAD+ to NADH and produce another CO2. Now we have a-ketoglutarate which hydrolyzes succinyl-CoA and in the conversion produces another NADH and CO2 pair. Succinyl-CoA synthase phosphorylizes GDP into GTP and also produces HS-CoA. Now we've got succinate, which becomes succinate dehydrogenase and FAD in converted into FADH2. This leaves us with fumarate, which becomes fumarase after the addition of a water, and then we have malate, which becomes a dehydrogenase as the final NAD in converted into NADH. Electrons from the FADH2 and NADHs are used for ATP production.

I'm just guessing but if ATP is the final product then is ADP the original material being upgraded? Now we are talking about photosynthesis or is this also happening in human mitochondria?

Help me?

Just aman

Both. ADP (adenosine diphosphate) undergoes non-cyclic phosphorylation via chemiosmosis and the electron transport chain to add another phosphate group (P_i) and becomes ATP (adenosine triphosphate).

Thanks faf, but I was looking for an acronym for the main steps in glycolysis and the intermediate enzymes that catalyze the reactions.

 

I'm just guessing but if ATP is the final product then is ADP the original material being upgraded? Now we are talking about photosynthesis or is this also happening in human mitochondria?

 

Talking about animal cells here. Pyruvate [the starting molecule for krebs] is formed from breaking down glucose molecues in a process called glycolysis.

 

The main point of the krebs cycle (faf's post) is to produce NADH and FADH2. These are used to carry electrons to the "electron transport chain" to create ATP, which faf devoted one sentence to

 

Basically the electron transport chain is a series of molecules the electrons "fall down", finally reaching oxygen. Kind of like a ball bouncing down a staircase. The energy released from this fall is used to create ATP from ADP + Pi.

 

 

When I studied cellular respiration last year, I could not believe all this happens in one tiny cell. Amazing stuff.

You asked about both, I'll post all the steps of glycolysis later

It's not really part of the Krebs cycle, thats why I only had a sentence about it. It's actually another paragraph. There's something like 8 intermediates with O2 at the end.

Yea, I'm just saying that post could lead one to believe that the purpose of krebs was to produce ATP. Taken in context, it does..but when analyzed alone, basically it produces NADH and FADH2

Wow - this takes me back.

 

Amazing what you forget in a few short years, isn't it?

As promised, the steps of glycolysis:

 

We start off obviously with glucose, which is immediately converted to fructose phosphate by the use of one ATP, then phosphorylated again with a second ATP to a compound with the phosphate groups at the C1 and C6 ends of the fructose chain to form Fructose 1,6-bisphosphate. This is split into 2 3 carbon monophosphates called glyceraldehyde 3-phosphate. These are oxidized into acids as NAD+ is reduced to NADH. C1 is phosphorylated to form an acyl phosphate. Now we have 2 1,3-Bisphosphoglycerates. The C1 phosphate groups are then used to phosphorylate 2ADP to produce 2 ATP. Now we have two 3-phosphoglycerates, which react to form two phosphoenol-pyruvates. The phosphate groups are pulled off by ADPs, leaving us with 2 pyruvates for the Krebs cycle.

You forgot the intermediate enzymes

 

Bah, the only one I remember is phosphofructokinase, which transfers a phosphate group from an ATP to the sugar.....I think.

Hexokinase, phosphoglucose isomerase, phosphofructokinase, aldoase, dihydroxyacetone phosphate, triose phosphate isomerase, glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase, phosphoglyceromutase, enolase, pyruvate kinase. In that order. Want the free energy values?

For the TCA the intermediates are pyruvate dehydrogenase, citrate synthase, aconitase, isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, succinyl CoA synthase, succinate dehydrogenase, fumarase, and malate dehydrogenase.

Thanks Faf. I probably graduated so easily because they didn't know all this when I was a pup and they could put the whole cycle on a blackboard in about six steps. I had no idea so many enzymes were involved. Sounds like we should take our vitamins to keep the processes working. If we're short on one element then the whole chain goes down the tubes.

Just aman