AP Bio 2026 FRQ 3 – Cyanide, CCO, ATP, and Lactic Acid

Added: 2026-05-09

[00:00:01]Hello, my name is Mr. Chipman and this is question three from the 2026 F FRQ uh AP Biology. Here we go. We've worked our way through the long questions. Now we're to the short question. This one's funny. This one's giving me a little more trouble than [clears throat] the other ones have. It's kind of went back and forth on some stuff. Some of it's just cuz I can't read. All right, so let's look at it together. Uh cyanide is a chemical that affects enzyme cytochrome C oxidase. Key enzyme mitochondrial electron transport chain at high cyanide concentrations. CCO activity is much lower when no then when no cyanide is present at low concentrations of cyanide. CCO activity is slightly higher than when no and then you have the table there. Uh some strains of bacteria produce cyanide which they then release into their environment. Other strains of bacteria do not produce cyanide. Uh researchers grew both types of bacteria in a high concentration nutrient medium. Then isolate the medium from the bacteria.

[00:01:05]One half of each medium sample was left at high concentration while the other half was lowered. Okay, good. So far concentration of the medium. Yes. Okay, good.

[00:01:19]And then to study the effects of cyanide on mamalian cells, researchers then added four samples of media to the cells and culture dishes as shown in table two. They measured ATP and lactic acid production mamalian cells each four treatments. Okay, good. And then we have the treatments. We have uh whether or not cyanide was in the medium and then the concentration of the medium. So this is where I messed up here is I was thinking it was nutrient concentration.

[00:01:49]It's not. It is the concentration of the cyanide in the medium. And so that clears things up immediately there. As I was looking through that, you know, it's I, you know, we've talked about this before and if you've listened to me at all, you know that I will say that there's tricky questions on purpose and I believe this to be one of those. Some of you guys are like, "Well, that's not tricky at all." Well, for me it was, right? That's the idea. It's just going to hit different people different ways.

[00:02:16]All right, [clears throat] let's look at part A. Describe the advantage to cells of producing ATP from one molecule of glucose by aerobic respiration rather than glycolysis alone. Uh the advantage is that the glucose uh in aerobic respiration produces a lot more ATP than than glycolysis alone. You could get into the numbers here if you wanted to.

[00:02:39]you know, uh it's two net ATP for glycolysis 34 to 36 ATP or was it 36 to 38 or one of those? Uh but I think that if you just said the advantage is is that a lot more or more um is produced from a respiration than glycolysis alone that should be sufficient. Um since those numbers aren't required by this class, um I think just knowing that one is much more efficient would be helpful.

[00:03:09]Part B, identify the two treatment groups that served as controls. Okay, good. And so now that I know um that this has to do with the concentration of the now I'm like double concentration of the medium whether or not cyanide is in there. Okay. And high and low. So I believe that three and four serve as control groups. I originally had one and three. And the reason that I had one and three is because these would be known uh groups because we know what happens when you have cyanide and when you don't, right? And so um but I'm going to go with three and four final answer. And then part C based on the information provided predict the treatment group that is likely to have the the highest ATP. So because cyanide is there but it's a low concentration which we know that lower concentration slightly increases CCO activity then I'm going to go with group two for this one.

[00:04:10]Change my original answer. My original answer here was three. So yeah just just a reading question. This class is a reading class that masquerades a science class. Or you could just even say science is really just reading with maybe a little math depending on which science you're taking. Uh the researchers claim that cells in the CCO activity is inhibited uh will show an increase in lactic acid production which makes sense. If you shut down CCO, you're shutting down the ETC, which means that oxygen is not going to be the final electron acceptor, which means that NADH is going to have to drop its electrons off someplace else, which is fermentation. Support the researcher's claim. Researchers correct because of everything that I just said. Basically researchers correct because of the definition of fermentation right u because if there's no longer oxygen is no longer the final electron acceptor because the etc is shut down then lactic acid production is going to increase that is all question three let me know if you have questions in the comments down below we're going to be working on four five and six Next.