If you know glycolysis really well....

[JeanettePNP, MSN, RN, NP]

I have a couple questions for anyone really good at explaining cell respiration.

When a molecule of NAD+ is reduced to NADH and H+, where does the extra H come from? I know that 2 hydrogen atoms are needed, because NAD+ needs one H and 2 electrons, so you have one proton (H+) left over. But where did it come from? Between step 4 and step 5 of glycolysis, an H is removed from glyceraldehyde and replaced with O~P. That is the only H I see that's missing. Where did the O come from, and the other H? If it's coming from H2O, then there would still be an extra H somewhere.

Also in the last step of glycolysis - in step 8, the first carbon is CH2, and in step 9, it's CH3. Where does the H come from? I don't see it accounted for in the equations.

As long as I'm at it, I'm totally lost with the electron transport chain. I understand that electrons are being passed to lower energy levels and energy is being harvested to change ADP to ATP. But I'm really lost as to where the hydrogens are going. I don't understand the whole gradient thing.

I hope there's someone here who recently took bio and can help me!

[carolinapooh, BSN, RN]

You've answered your own question.

Water is H2O. NAD+ gets reduced to NADH, and H+ is left over. (Yes - it comes from water.)

There are your two hydrogens. I have a great pic of this cycle in my text if you need it; I can scan and email it to you.

I take it you're sticking with at least your prereqs for now? I'm so glad!!

[carolinapooh, BSN, RN]

Another thing - when we took our test on this, we had to show "inputs and outputs". I physically drew the cycle out on a piece of paper, and showed the inputs on one side and the outputs on the other, with arrows. (Sorta hard to explain in the abstract....) It really helped me learn it. Maybe you could try that.

[JeanettePNP, MSN, RN, NP]

Thanks, Carolina. I have not started taking any college courses yet, that's because I didn't really start thinking seriously about school until December, and it was too late to register for the spring term. I will start in the summer or fall. But in the meantime I'm teaching myself as much science as I can using textbooks and online resources. That will hopefully ease some of the pressure once I start class. I am really, really enjoying it. I always liked science and I feel better now that my brain cells are not going to waste. If I can apply those same brain cells to helping people (i.e. nursing), even better.

OK I see how it all adds up. I don't know why the diagram in my book doesn't indicate that H2O is entering into the picture though. It accounts for everything else, but you have to figure out that an H2O is being used up?

[JeanettePNP, MSN, RN, NP]

Carolina: How detailed were your tests? I am using various texts and some are more detailed than others. Did you have to know the structure of every amino acid? Of every molecule in glycolysis and Krebs cycle? Now I'm really just focused on getting the general picture but I want to know if I'll need that for later.

[carolinapooh, BSN, RN]

The problem is it depends on what your instructor thinks is important. We didn't have to know amino acid structures (that seems very in-depth to me; we learned it when I took organic chem but it wasn't in A&P or in Microbiology). We did have to know the inputs and outputs for cellular metabolism.

For most reactions like glycolysis, you have to have water - you need a source of O and H+. If you need those atoms, chances are the cell/organism is going to get them by breaking down water. It took me an entire semester of organic to get this through my head until it was automatic, so don't feel lonely in that. (I'd be doing the same thing, staring at some reaction mechanism and getting completely confused - where in the heck did the H+ come from? Oh - the water. THE WATER THAT'S RIGHT THERE. :) )

Could I recommend MICROBIOLOGY DEMYSTIFIED? It's a great sourcebook for breaking down complex topics into something a bit easier to understand. I bought it and use it with my Micro text as a supplemental source. There are a bunch of books in that series - including Chemistry, General Biology, and A&P. They're sort of like the "for dummies" series (in fact, the graphics in them look very similar, so I wonder if they're from the same publisher or group). I got mine at Barnes and Noble. It has really come in handy. Of course, there are topics in there that it summarizes in a paragraph and the text takes nine pages - but when we started Microbial Genetics I took preliminary notes based on that book, and then just filled them in with details from my textbook. I studied them, the study guide our instructor gave us, and the lecture handouts. I got a 94 on the test, so I guess it wasn't such a bad strategy!

The Demystified book is even set up exactly like my textbook.

You could also look at http://www.excelsior.edu - they have free study guides that you can download for various courses (they might make you register, but it costs nothing to do that). They are set up like outlines and give a good guide to studying the subjects. I know they have Micro and A&P. Keep in mind that those outlines are geared toward their own exams, but the key points you need to know would be the same, and I think you would find them useful for your purposes.

I think what you're doing is great. I'm sure it helps to keep your interest up and makes use of free time that you might have. And it certainly won't hurt! It also seems like something I myself would do so I wouldn't feel idle.

I'm actually in Micro right now; you can PM me anytime if you have questions.