Krebs cycle help

jenrninmi, MSN, RN · Nov 1, 2004

Ugh! Does that bring back bad memories - from biochem especially! I thought I had a website saved in my bookmarks, but I don't see it. I wish I could help you, I just want to wish you luck! I hated learning that!

jenrninmi, MSN, RN · Nov 1, 2004

Acutally, here's one I found right away and seems to explain it well: http://www.science.smith.edu/departments/Biology/Bio231/krebs.html

This is a good one too and I think this is what I used to help me when I had it:

http://www.jonmaber.demon.co.uk/tcasteps/

This one too: http://www.people.virginia.edu/~rjh9u/krebs.html

http://www.people.virginia.edu/~rjh9u/krebsum.html

http://www.stark.kent.edu/~cearley/pchem/Krebs/Krebs.htm step by step.

Hope these help!

Achoo!, LPN · Nov 1, 2004

Thanks ! :)

DenaInWyo · Nov 1, 2004

yes, thanks! I have a test in micro tonight and those were really helpful.

Deana

purplekath · Nov 1, 2004

This is very simplified, but I'm sure you've read all the details of this in your book. When I was studying for this, I read the section several times to get an "overall picture", then placed the following onto flashcards and just drilled them into my brain:

KREBS CYCLE

2 molecules of pyruvate for every molecule of glucose that enters glycolysis.

(1 glucose = pyruvate)

Pyruvate easily enters the matrix of the mitochondria into a circular pathway - the Krebs cycle.

Krebs cycle:

1. Each pyruvate converted to a two-carbon fragment, which is attached to a co-enzyme called CoA or coenzyme A.

2. The enzyme that accomplishes this is a large enzyme known as the pryruvate dehydrogeneses complex. It is inhibited by high ATP, Acetyl-CoA, and NADH. In the process NAD+ is converted to NADH + H+ and CO2 (a carboxyl group) is lost. Therefore over all simplified Krebs cycle is as follows...

2 pyruvate = enters krebs cycle = yields: 6 CO2 (waste) = ATP to cell to do the work

8 NADH

2 FADH

2 ATP

If you need to take it further into the Electron Transport Chain, drop me an email on [email protected] and I'll send you a doc I made up explaining it fairly simply. Best of luck!!

purplekath · Nov 1, 2004

(1 glucose = pyruvate)

....this was meant to be 1 glucose = 2 pyruvate!!

Achoo!, LPN · Nov 1, 2004

Thanks so much!!

longroadahead · Nov 2, 2004

I thought it had to be converted to Acetyl-CoA before it entered the Kreb's Cycle ("at the doorway to the Kreb's cycle" - can't believe I remembered that from my instructor's notes...)

purplekath · Nov 2, 2004

Yes that's true -- it depends on where you read as to where the Kreb's cycle technically begins. Your "doorway" concept is a good one. The actual glycolysis of glucose to pyruvate takes place in the cytoplasm, but it then goes through the "doorway" to the mitochondrial matrix where the pyruvate is oxidised.

Because the glycolysis bit can take place without oxygen (fermentation), you can still make ATP without needing to go into the oxidisation phase...so in that respect it's like a separate step. But in the presence of oxygen, it forms a part of the Krebs cycle (ie: the Krebs cycle cannot occur without this step, so in that respect it's part of the Krebs cycle).

When I was studying this 50% of the stuff I read said it was part of the Krebs cycle, and the other 50% said that it was a separate step that occured BEFORE the Krebs cycle! In the end, I put my lecturer's opinion in my exam! lol

Dublin37 · Nov 2, 2004

EEEeeeeeeeeeeeeeeek, i'm having flashbacks! Dang, other than memorizing the number outcome, i really don't get it!

stressgal, RN · Nov 3, 2004

Not knowing the nitty gritty about the krebs cycle has only cost me three points on an exam. I'll gladly give those up for the survival of neurons that would be destroyed during my frustration. Just concentrate on the products.