C3, C4 & CAM Plants - Video Tutorials & Practice Problems
On a tight schedule?
Get a 10 bullets summary of the topic
1
concept
C3, C4 & CAM Plants
Video duration:
4m
Play a video:
Video transcript
In this video, we're going to begin our introduction to the differences between C3, C4, and CAM plants. And so it's important to recall from our previous lesson videos that photorespiration is actually a bad thing for plants. Because photorespiration, recall from our previous lesson videos, will waste energy in the form of ATP and NADPH to make carbon dioxide gas or CO 2, which is really the opposite of what photosynthesis does, which is consume or use carbon dioxide. And so ultimately photorespiration is going to make photosynthesis inefficient and that's why photorespiration is a bad thing for plants that plants want to try to avoid or minimize. Now, here in this lesson, what we're saying is that in hot temperatures, it actually turns out that it's the C3 plants specifically that are most susceptible to photorespiration. But some other plants have been able to evolve a solution for photorespiration, and this includes the c 4 and the CAM plants. And so the c 4 and the CAM plants have evolved a slightly different variation in the way that they do photosynthesis that allows them to avoid or minimize photorespiration. And so this allows c 4 and CAM plants to better withstand hot temperatures that c 3 plants are not able to withstand those hot temperatures. And so once again, c 4 and CAM plants are able to better withstand hot temperatures because they've evolved a solution to be able to minimize or avoid photorespiration. And so moving forward in our course in our next video, we're gonna talk more about the differences between C3 plants, C4 plants and CAM plants. But for now, let's take a look at this image down below that we have here, which is really a map of our lesson on photosynthesis And notice already in our previous lesson videos, we've talked about the light reactions and the Calvin Cycle, which are the 2 stages of photosynthesis. So because we've already talked about these, that's why they're grayed out in this image here. And we did talk about the light reactions and the Calvin cycle reactions, under the conditions where the stomata were in an open position, where gas exchange was able to occur. But also in our previous lesson videos, we talked about how in hot temperatures, plants will close their stomata to prevent dehydration. But when they close their stomata, they also are going to prevent gas exchange. And by preventing gas exchange, this is going to lead to photorespiration. And here in this video, we're telling you that it's actually the c three plants that are most susceptible to photorespiration. And so here, we're indicating that we're calling it C3 photorespiration. Now again, C3 photorespiration is a bad thing for plants that wastes energy and makes carbon dioxide. So plants want to be able to avoid or minimize photorespiration, and some plants have actually been able to evolve a solution. And this includes the c 4 and the cam plants, which have evolved a solution for photorespiration to be able to withstand hot temperatures and avoid photorespiration. And so you can see here in our image that we have some plants that are able to avoid photorespiration and this includes again the c 4 plants and the CAM plants. Now notice that right next to the C4 plants, we have this C4 bomb, and later in our next video, we're going to talk about exactly how this C4 bomb can help you remember C4 plants. Then also notice that next to the cam plants over here, we have this camel wearing some pajamas. And so again, in our next video, we're gonna talk about how thinking of a camel wearing pajamas can help you remember cam plants. But for now this here concludes our brief introduction to, c three, c four and CAM plants. And again, in our next video, we're gonna talk more about the differences between C3, C4 and CAM plants. So I'll see you all in that video.
2
concept
Comparing 3 Types of Photosynthetic Plants
Video duration:
15m
Play a video:
Video transcript
In this video, we're going to be comparing the 3 types of photosynthetic plants, which are the c three plants, the C4 plants, and the CAM plants. And so it turns out that the vast majority of plant species are actually C3 plants. And so the C3 plants actually perform the standard photosynthesis process that we already covered in our previous lesson videos. And so the C3 plants will perform the light reactions and the Calvin cycle exactly as we discussed them in our previous lesson videos. And so really when it comes to the c three plants, really there's nothing new here. It's really just review information from our previous lesson videos. And so the reason that C 3 plants are called C 3 plants is because the very first stable molecule that's produced during the Calvin cycle is a 3 carbon intermediate or a c 3 intermediate. That's why it's called c 3 plants. And also during, c 3 photosynthesis, c 3 plants are going to only have one round of carbon fixation. And so carbon dioxide gas is only going to be affixed to another molecule just one time and that is during the Calvin cycle. And also with c three plants, it turns out that the light reactions, the light reactions and the Calvin cycle are both going to occur in the same exact cell. And so that cell is going to be the Mesophyll cell. And so when it comes to the c three plants, we can see a reminder of the c three plants down below in our image over here on the far left hand side. And so over here what we have are the c 3 plants. And so when it comes to the c three plants again, it's really just review from our previous lesson videos. There's really nothing new when it comes to, c three plants and c three photosynthesis. And so when it comes to the c three plants, it turns out that the light reactions and the Calvin cycle reactions are going to occur in the same exact cell, the mesophyll cell. Now notice that the light reactions is not being shown in any of these images here, and we're focusing mainly on the Calvin cycle. And so, in c three plants, the light reactions and Calvin Cycle are going to occur in the same exact cell. And so notice that here we only have one cell and that is the Mesophyll cell. And so, you can see carbon dioxide coming into the Calvin cycle and glucose being produced here in the Calvin cycle. And so here we have c 3, leave it be, and that's because again c 3 plants just use the standard c 3 photosynthesis that we've already talked about. And so again there's really nothing new here, it's all review. So c 3, leave it be with how we already discussed it. So now we're gonna turn our attention to the next type of plant, the c 4 plants. And so the c 4 plants and the CAM plants have both evolved slightly different variations in the way that they perform photosynthesis. And so these slightly different variations that the C4 and CAM plants have evolved have allowed them to withstand hot temperatures by avoiding or minimizing photorespiration. And so, we're gonna focus in on the C 4 plants first. So the C 4 plants are called c 4 plants because the very first molecule that's gonna be made is a 4 carbon intermediate, f 4 c intermediate or a c 4 intermediate. And one major difference between c 3 and c 4 plants is that in terms of the number of carbon fixation rounds, the c 4 plants use 2 carbon fixation rounds instead of just 1 carbon fixation round like c 3 plants. And so we'll be able to talk about these carbon fixation rounds down below once we get to our image. Now what's also another really big difference between c 4 plants and the c 3 plants that we're used to is that c 4 plants, the light reactions and the Calvin cycle reactions occur in different cells. And so we'll be able to see this down below in our image as well of the c 4 plants. And so, unlike the c three plants where the light reactions and the Calvin cycle reactions occur in the same cell, with c 4 plants the light reactions will occur in one cell type and the Calvin cycle reactions will occur in a different cell type and so they occur in different cells. Now, this 4 carbon intermediate here is actually gonna be the key to allowing c 4 plants to minimize photorespiration. And that's because this 4 carbon intermediate, this 4 c intermediate or c 4 intermediate, is going to be useful in supplying additional carbon dioxide, c o two, when carbon dioxide levels get really, really low from closing the stomata in warmer and drier temperatures. And so let's take a look at our image down below right here in the middle image. This is where we are showing you the c 4 plants and so we can go ahead and label them as the c 4 plants. And, standard, example of c 4 plants are corn. And so, what you'll notice is that in, c 4 plants, the, there is going to be the light reaction and the Calvin reaction that are going to occur in different cells. So notice here what we have are 2 different cells. We have the mesophyll cells, which are up above right here, and then down below what we have are the bundle sheath cells, and so those cells are down here. And notice that the bundle sheath cells down below are the ones that will be performing the Calvin cycle, And the mesophyll cells up above here are the ones that are actually gonna be performing the light reactions. And also in c 4 plants, there is going to be 2 rounds of carbon fixation. And so you can see here in the mesophyll cells, Carbon dioxide is going to be able to come into the Mesophyll Cell and it's going to be affixed to a 3 carbon molecule to make a 4 carbon intermediate. And the 4 c intermediate, the c 4 intermediate is really why these plants are called c 4 plants. And so this 4 c intermediate is really really important because what it does is it's fixing carbon dioxide, and storing carbon dioxide as this 4 carbon intermediate. And so whenever carbon dioxide levels get really really low, this 4 carbon intermediate can be a supply, can provide additional carbon dioxide. So you can see c o two production here is able to occur, and the 4 carbon intermediate is able to be essentially converted to, supply additional carbon dioxide whenever they get low. And this carbon dioxide, ultimately it's going to make its way into a second cell, again, the bundle sheath cell, and the bundle sheath cell is going to fix the carbon dioxide here a second time in the Calvin cycle to produce glucose. And so ultimately, what we can see is that carbon dioxide or CO 2 is getting fixed up here in the mesophyll cell to form a 4 c intermediate once, and then the 4 c intermediate is really just a way to store carbon dioxide. So whenever carbon dioxide gets low, carbon dioxide production can occur. So here we have our c o two molecule again, and the c o two molecule can get fixed a second time in the Calvin cycle within the bundle sheath cell. Now one way to help you remember that c 4 plants will use 2 different cells, the mesophyll cell and the bundle sheath cell, is to realize that c fours are actually explosives like bombs. So if you ever if you know anybody that plays video games like Call of Duty or something like that, you'll know that c fours are explosives or bombs. And so, when you think of c 4 plants, even though really c 4 plants have nothing to do with explosives, you can think of these explosives and what explosives do or bombs do, when they explode, they basically break things up into pieces. And so, when you think of c 4 plants, you can think of c 4 explosives and think of things getting broken up into pieces, and really that's what we have here. We have, two pieces. We've got the mesophyll cell piece and we've got the bundle sheath cell piece down below. And so, the c 4 plants are gonna be different in this respect, of having 2 different cells utilized. And so now what we're going to do is move on to our 3rd and final type of plant which are the CAM plants. And the CAM plants are similar to the C4 plants in that they also form a 4 Carbon Intermediate, a 4 c intermediate, just like the c 4 plants do. But the camp plants are different. Well, actually the CAM plants are similar to the c 4 plants in that they have a 4 carbon intermediate and that they have 2 rounds of carbon fixation. So this is how they are similar, right here. But what's different between the c 4 and the CAM plants is that the CAM plants, have the light reactions and the Calvin cycle reactions in the same cell. And so, the same cell is gonna be, similar to how the c three plants perform. But the CAM plants, again, they're different than the c three plants because they form a 4 c intermediate that's different than c 3, and they also have 2 rounds of carbon fixation, which is again different than the c 3. But really what makes the CAM plant so unique is that the carbon fixation rounds, these 2 carbon fixation rounds are going to occur at different times of the day. And so essentially what's going to happen is that the stomata of camp plants are going to be open. They're going to be in the open position during the night when the temperatures are cooler, and then the stomata are going to change to their closed position during the day when the temperatures are hotter so that they can avoid dehydration. And so let's take a look here at our CAM plant image down below over here on the right hand side and so we can go ahead and label these as the can plants. And a classic example of can plants are going to be, cacti or a cactus like what you see in the desert. And so what's important to note here is that here with the camp plants there's only one cell type here. We only have the mesophyll cell, so, there's only one cell type unlike the c 4 plants, which again, they have 2 cell types, the bundle sheath and the mesophyll cells. So the CAM plants only have one cell type and, they still, fix carbon twice. So you can see carbon dioxide here is gonna make its way in and get fixed and form a 4 c intermediate, similar to how there's a 4 c Intermediate formed in c 4 plants. And this 4 c Intermediate is again gonna act as a storage form of carbon dioxide. So when carbon dioxide levels get low, this 4 c Intermediate can provide additional carbon dioxide or c o two production, and then this carbon dioxide can be fixed a second time here in the Calvin cycle to form glucose. And so, what you'll also notice is that the carbon fixation is occurring at different times of the day. The first carbon fixation is occurring at night, which you can see up above here, and then the second carbon fixation right here is occurring during the day. And so ultimately what happens is, is again, at night, when the temperatures in the desert are much much cooler, the CAM plant can have its stomata open without risking dehydration. And so when the stomata are open carbon dioxide can come in and the plant can store a whole bunch of carbon dioxide at night as 4 c intermediates. And then when the daytime comes around, and the temperatures get much hotter, the, camp plant needs to close its stomata. And when it closes its stomata, the carbon dioxide levels get low within the cam plant. However, because at night it stored a whole bunch of 4 carbon intermediates, the 4 carbon intermediate can provide carbon dioxide during the day so that the Calvin cycle can run during the day and again perform, the Calvin cycle to create glucose. And so ultimately, the key feature here of the canned plants is that they are going to occur at different times of the day. 1, one carbon fixation occurs at night, the second carbon fixation occurs during the day. And so something that can help remind you of, what the CAM plants do is to think that cam plants are kind of like a camel. And camels, we know they live in really hot and dry, environments like deserts. And so if you think of a camel wearing pajamas, then you'll know that, the this will help remind you that camp plants will perform their carbon fixation at different times of the day. The first carbon fixation is going to occur at night, and that can help remind you, the pajamas can help remind you of that. And then of course, the second carbon fixation is going to occur during the day. And so really this is, our brief introduction that's comparing the 3 types of photosynthetic plants, the c 3 versus the c 4 versus the CAM plants. And we'll be able to get some practice applying the concepts that we've learned here as we move forward in our course. So I'll see you all in our next video.