“Teach me,” she said.

[Cecily]

I was driving at that. Extremely inefficient and borderline disrespectful use of my time, pretttty sure our manual / text doesn’t have a differential reference, but I have a much better idea of how the tests operate than I got while scrambling to go through the physical motions rushed in the lab. I gained a few points in research and found some sources I plan to come back to help with course and personal interest.

From the top of my head (and this is all “new” information acquired today I’ve long since forgotten about when I did it before) :

O-F tests how / if an organism metabolizes sugar, seeing if ferments glucose in the presence of oxygen or if oxygen is toxic to it. That’s alot of variables that I haven’t quite gotten my head around, and I think we’re basically we’re seeing how deep into the Krebs cycle something gets, oxygen needed for oxidative phosphorylation in aerobic respiration’s electron transport chain = most efficient use of glucose for ATP.

Hazy on krebs, but I think each turn gets you 30+ 2 or 4? some ATP. Earlier step of glycolysis is way less efficient, so I’d make the assumption that anaerobic organisms reproduce much slower simply due to less available energy than ones that can survive in O2. Need to ask if I’m right on that.

Triple sugar iron test I need to look into more because the results are complicated. There’s like 8 different variables, glucose fermentation or glucose AND sucrose and or frutose, and also if it reduces sulfur. There’s also an indicator for metabolism of animal proteins. There’s a reaction with acid from fermentation that turns into black percipitate when sulfwr reduction happens.

Phenol red broth, this is the only one I actually know the indicator for (hint: phenol red) and I need to fix that in the future, but this can be glucose/ sucrose/ frutose as a differential, I’m assuming. But what it does is change color to yellow from red if fermentation happens when the ph drops to 6.8 or lower from the acid. If some p word happens the solution the solution turns pink from the alkaline end products. There’s also a tube floating in the solution that gets a bubble in it if fermentation produces gas. That gives you 3 or 4 results, depending.

As far as what bacteria does what, that’s all white noise atm and I need to see how relevant knowing that is to my grade. I think the concepts and characteristics are the focus here. The big picture in this lab from what I can see is these are simply various ways to test for fermentation of carbohydrates with slightly different variables.

[Cecily]

Question I have is wtf is fermentation? Lol. Feel like that’s a bad point to miss! Krebs cycle is fucking scary to look at and I need to learn the simplified version again to really get this.

Ok so it’s glucose molecule -> glycolysis -> two pyruvates and depending on O2 availability it goes either through oxidative respiration (big atp) or fermentation (acid, gas, alcohol byproducts depending on type of fementation).

I thought fermentation happened under anaerobic conditions and O-F test had me thinking it happened in both.

Fermentation = 2 ATP per glucose
Krebs = 36 + 2 ATP per glucose

Legit scared of this thing. I used to know it.
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https://wikispaces.psu.edu/display/2...ric+Acid+Cycle

[DMN]

Originally Posted by Cecily [You must be logged in to view images. Log in or Register.]

Question I have is wtf is fermentation? Lol. Feel like that’s a bad point to miss! Krebs cycle is fucking scary to look at and I need to learn the simplified version again to really get this.

In micro the definition is generally: the ability to metabolize sugars(produce ATP) without oxygen(anaerobically).

[DMN]

Originally Posted by Cecily [You must be logged in to view images. Log in or Register.]

I thought fermentation happened under anaerobic conditions and O-F test had me thinking it happened in both.

No, the F in OF is specifically for fermentation. if you get a change in PH in the "F" part of that test, the organism can use fermentation for a metabolic pathway.

[Cecily]

Originally Posted by DMN [You must be logged in to view images. Log in or Register.]

In micro the definition is generally: the ability to metabolize sugars(produce ATP) without oxygen(anaerobically).

Word. Thank you.

Originally Posted by DMN [You must be logged in to view images. Log in or Register.]

No, the F in OF is specifically for fermentation. if you get a change in PH in the "F" part of that test, the organism can use fermentation for a metabolic pathway.

Ohhh ok. So if it’s oxidative in open medium and ferments in sealed it has both pathways? And I guess they can be oxidative only and fermentative only. Or just not mess with that sugar. Thank you! That helps me get it.

[DMN]

Originally Posted by Cecily [You must be logged in to view images. Log in or Register.]

Word. Thank you.



Ohhh ok. So if it’s oxidative in open medium and ferments in sealed it has both pathways? And I guess they can be oxidative only and fermentation only. Or just not mess with that sugar. Thank you! That helps me get it.

99% of the time the answer is yes, but there are weird exceptions in much of biology. I'm not quite sure what you mean by "I guess they can be oxidative only and fermentation only".

[Cecily]

One pathway or the other. Or both.

Aerobic respiration only
Aerobic and anaerobic respiration
Anaerobic respiration only

It seems like this could be a differential for aerobes, facultative anaerobes, and anaerobes.

[TheSurgeon]

Originally Posted by Cecily [You must be logged in to view images. Log in or Register.]

Question I have is wtf is fermentation? Lol. Feel like that’s a bad point to miss! Krebs cycle is fucking scary to look at and I need to learn the simplified version again to really get this.

Ok so it’s glucose molecule -> glycolysis -> two pyruvates and depending on O2 availability it goes either through oxidative respiration (big atp) or fermentation (acid, gas, alcohol byproducts depending on type of fementation).

I thought fermentation happened under anaerobic conditions and O-F test had me thinking it happened in both.

Fermentation = 2 ATP per glucose
Krebs = 36 + 2 ATP per glucose

Legit scared of this thing. I used to know it.
[You must be logged in to view images. Log in or Register.]
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https://wikispaces.psu.edu/display/2...ric+Acid+Cycle

So, no shit, I spent a lot of time memorizing the entire CAC for the MCAT, knowing, just knowing they would ask a question that required you to memorize it. The one question about it on the test they had the entire cycle displayed in an image involving the question. Such a god damn waste of time.

[Cecily]

lol [You must be logged in to view images. Log in or Register.]

[DMN]

Originally Posted by Cecily [You must be logged in to view images. Log in or Register.]

One pathway or the other. Or both.

Aerobic respiration only
Aerobic and anaerobic respiration
Anaerobic respiration only

It seems like this could be a differential for aerobes, facultative anaerobes, and anaerobes.

Yes but that test won't perfectly differentiate those three. You could have an obligate anerobe that grows at the bottom of the "o" tube where there is little to no oxygen. So it might look exactly like a facultative anaerobe.