Glycolysis, Krebs cycle, ETC relationship

[callmesubo]

Can someone please connect the dotS for me? I understood and memorize the steps but having difficulty connecting these three in one string. Any explanation will help.

---

Members don't see this ad.

 

[dushash]

Can someone please connect the dotS for me? I understood and memorize the steps but having difficulty connecting these three in one string. Any explanation will help.

All living systems need energy. We get energy from food. When we eat food ----> Glycolysis breaks down carbs (Glucose) to Pyruvate. Then depending if O2 is present or not path divides. If no O2 present, Pyruvate is converted to Lactate (like in muscles) and this path is a dead end basically as it can go for limited amount of time. If O2 is present then Pyruvate enters Mitochondria where it undergoes further breakdown to Acetyl-CoA and then via Krebs cycle this Acetyl-CoA breaks down to CO2 and gives energy/electron rich molecules like NADH/FADH2 and then they are used via ETC that actually generates ATP - main energy currency in our body. That's all it is in short.

Now of course you need to know how this process is regulated in different states. If in well fed state - Acetyl-CoA may be converted to Fatty Acids in Mitochondria instead of going into Krebs cycle and ETC. Also proteins, AAs and fats can have their own pathway slightly different from Carbs pathway, but eventually they all join at some point in the pathway: for example proteins and AAs as well as fats can enter Glycolysis cycle at the point where Pyruvate is generated or at the point where Acetyl-Co-A is formed. Many processes are reversible, but some are not: for example once Pyruvate is converted to Acetyl-CoA you can't convert it back to Pyruvate to use it to generate Glucose - in that case Acetyl-CoA can only be used to produce Ketones which will act as Glucose substitution for brain to feed on (this happens during long starvation mode). There are some additional pathways except Glycolysis, Krebs and ETC - for example Pentose Phosphate Pathway - needed for nucleotide synthesis itself.

I think it's better if you watch some videos on metabolism in general - to get BIG picture - overview from bird's eye so to speak. But then eventually you still have to explore different pathways and relationships between them on your own and memorize things - can't skip that. Doing questions on metabolism is essential too - to get things sorted in your mind.

 

[Doctor Dream]

dushash did a good job explaining I think, but if you're still stuck the REAL general purpose of each is....

Glycolysis - Takes glucose (which can be obtained in a number of ways) and breaks it down into pyruvate, while producing 2 ATP and 2 NADH
Linking step - converts pyruvate into acetyl-CoA, and reduces NAD+ to NADH.
Krebs cycle - Makes as many reduced coenzymes (NADH, FADH2) as possible. Acetyl-CoA enters Krebs, and goes through cycle, making 3 NADH, 1 FADH2, and 1 ATP.
ETC - this is where the body takes those reduced coenzymes it made in Krebs and glycolysis and uses them to make a H+ gradient in the mitochondria, by pumping protons across a membrane. This gradient is then used to power ATP-synthase, which makes ATP as the name suggests.

Also note that glycolysis happens outside mitochondria in the cytosol, Krebs and ETC are both inside mitochondria

 

[callmesubo]

All living systems need energy. We get energy from food. When we eat food ----> Glycolysis breaks down carbs (Glucose) to Pyruvate. Then depending if O2 is present or not path divides. If no O2 present, Pyruvate is converted to Lactate (like in muscles) and this path is a dead end basically as it can go for limited amount of time. If O2 is present then Pyruvate enters Mitochondria where it undergoes further breakdown to Acetyl-CoA and then via Krebs cycle this Acetyl-CoA breaks down to CO2 and gives energy/electron rich molecules like NADH/FADH2 and then they are used via ETC that actually generates ATP - main energy currency in our body. That's all it is in short.

Now of course you need to know how this process is regulated in different states. If in well fed state - Acetyl-CoA may be converted to Fatty Acids in Mitochondria instead of going into Krebs cycle and ETC. Also proteins, AAs and fats can have their own pathway slightly different from Carbs pathway, but eventually they all join at some point in the pathway: for example proteins and AAs as well as fats can enter Glycolysis cycle at the point where Pyruvate is generated or at the point where Acetyl-Co-A is formed. Many processes are reversible, but some are not: for example once Pyruvate is converted to Acetyl-CoA you can't convert it back to Pyruvate to use it to generate Glucose - in that case Acetyl-CoA can only be used to produce Ketones which will act as Glucose substitution for brain to feed on (this happens during long starvation mode). There are some additional pathways except Glycolysis, Krebs and ETC - for example Pentose Phosphate Pathway - needed for nucleotide synthesis itself.

I think it's better if you watch some videos on metabolism in general - to get BIG picture - overview from bird's eye so to speak. But then eventually you still have to explore different pathways and relationships between them on your own and memorize things - can't skip that. Doing questions on metabolism is essential too - to get things sorted in your mind.

Thanks a lot. That was one of the best explanation every. You really know your stuff.

 

[callmesubo]

dushash did a good job explaining I think, but if you're still stuck the REAL general purpose of each is....

Glycolysis - Takes glucose (which can be obtained in a number of ways) and breaks it down into pyruvate, while producing 2 ATP and 2 NADH
Linking step - converts pyruvate into acetyl-CoA, and reduces NAD+ to NADH.
Krebs cycle - Makes as many reduced coenzymes (NADH, FADH2) as possible. Acetyl-CoA enters Krebs, and goes through cycle, making 3 NADH, 1 FADH2, and 1 ATP.
ETC - this is where the body takes those reduced coenzymes it made in Krebs and glycolysis and uses them to make a H+ gradient in the mitochondria, by pumping protons across a membrane. This gradient is then used to power ATP-synthase, which makes ATP as the name suggests.

Also note that glycolysis happens outside mitochondria in the cytosol, Krebs and ETC are both inside mitochondria

Thank you very much. I understand it much better now. It's good to see 10-20 pages worth of material simplified in just few paragraphs!