Cellular Respiration

 

Cellular Respiration is one of the most important concepts in understanding Biology because it is what happens inside all of the cells of the human body and provides energy to keep our bodies alive. Watch the video to learn how Cellular Respiration works.

 

Below is a picture of a worksheet that goes along with the video. Feel free to download and use it; all you have to do is right clic on the pictures, save, and print!

 

Cellular Respiration Worksheet Page 1 

Cellular Respiration Worksheet Page 2 

 

 

 

Complete Video Transcript:

"Cellular Respiration is one of the most important concepts in understanding Biology because it is what happens inside a eukaryotic cell, inside all of our cells in our body where we’re making energy for our cells to survive and for all of the processes to happen that need to happen for a cell to stay alive.

 

So, I’m going to give you an overview here of cellular respiration and try not to get into the biochemistry too deep because I don’t want to confuse you. And then there will be an opportunity in other videos to really focus in on the Krebs cycle and the Electron Transport Chain.

 

So we’re dealing with an animal cell here in cellular respiration. I’ve got just two organelles up here: the nucleus, let’s just say the “brain” that holds the DNA, but then I’ve got the cytoplasm and the mitochondria. The mitochondria is sort of the factory that makes all of the energy that the cell needs. And the cytoplasm is the space in between the organelles, but it is not just space, there’s a whole bunch of molecules in there, and processes, so chemical reactions can happen inside the cytoplasm - we’re going to see that right here.

 

So, I’ve got my mitochondria down there at the bottom and I’ve got the blue that is my cytoplasm.

 

In cellular respiration the first thing that has to happen is something called glycolysis. Note that I put up there that there is no oxygen needed. Glycolysis is the breakdown of glucose. If you go all the way back to the videos I made before about photosynthesis, plants spend a whole lot of time and energy making glucose; they take in the sun’s energy, they breathe in carbon dioxide, they take in water and they make this glucose. And then we, as animals and humans, we eat those plants and we extract all that energy that the plants spent so much time making. So, they build it up, we break it down to get the energy back out of it.

 

Now, glucose is a six carbon molecule, there are other things on here, there are hydrogens and oxygens, and C6H12O6, but I am just representing it as a six carbon chain so we can track where these molecules are going and how they are breaking apart.

 

Glucose is going to get broken down, once it gets inside your body and it enters your cells, ok, so the process of glycolysis is going to break this down. Your body, or the cell has to invest a little bit of energy. It uses ATP, that ATP comes in and hits that glucose and it breaks off it’s energy, alright, so that energy is released which means we have ADP and that phosphate that was broken off. We’ve gone through the ATP and ADP cycle before in photosynthesis, same thing, only now this is happening inside an animal cell. So that energy slams into that glucose and it breaks it up into two separate carbon molecules. So we have two molecules now, each with three carbons. So we’ve broken this thing in half.

 

Now, when that happens, it's gone through some enzymatic reactions and things, and energy is released and these are rearranged, carbons are broken apart, and they are rearranged into something we call pyruvate. Alright, so here are two pyruvate, or pyruvate, depending on how you say it. And they’re not attached together, I’ve just got two of them over there, and when those form, alright, when we broke that glucose apart, energy was released. We needed a little bit of energy, ATP, to go in and break them apart but once that energy went in there and broke it apart, it released a bunch of energy. It released energy in the form of NAD, NAD is not the energy it is the carrier of that energy. We’ve got NAD+, if we go all the way back to photosynthesis, we had NADP+, in an animal cell though, in a eukaryote we have NAD+. Think of this as a wagon and right now it is an empty wagon that you’ve got a little kid pulling on down the road and it needs to get filled up with something.

 

So, when this glucose breaks apart it it does get filled up and it gets filled up with electrons - 2 electrons. So now we say that it’s got energy or it got potential. And, um, those electrons, when they’re bound on there, we can use those later on in another chemical process.

 

So now the name of this has changed to NADH, which is the oxidized version of NAD+, notice that little plus on there and I’ve got the two electrons attached on there. The other thing that happens is ADP, which was broken apart earlier, that phosphate gets reattached on ADP, so ADP is Adenosine DiPhosphate, now it’s Adenosine TriPhosphate. Okay, ATP: Adenosine TriPhosphate, it’s got three phosphate groups on it and it’s got a whole bunch of energy.

 

So, here’s glycolysis. This is all happening outside of the mitochondria, but not, once oxygen is present, that mitochondria can take both of these in - the pyruvate and the NADH, and it can use those to make energy.

 

So, pyruvate is going to enter in something called Stage 1 which is the Krebs Cycle and then the other pieces of energy over here, ATP and NADPH are going to be needed in Stage 2, which is the Electron Transport.

 

So I’m going to move this whole screen down so we can look right into the mitochondria.

So, I’ve moved this thing down, so now we can see all of our mitochondria there. Remember what we are looking at, glycolysis was the first step, now we’re looking - what happens when oxygen becomes available, which my oxygen magically appeared over there, and then these two pyruvate end up going inside the mitochondria. Now, when they get absorbed in there they actually go into the matrix. The matrix, so you can see I’ve tried to draw in the inner membrane inside the mitochondria, it’s not very pretty but it will work. There’s a space in between the inner membrane called the matrix.

 

So, this goes into the matrix and a whole series of chemical reactions happens in there, which is called the Krebs Cycle. Now, there will be another video that goes into detail on the Krebs Cycle but just for right now, what happens is those carbons get broken apart and rearranged and what spits out of the Krebs Cycle is ATP, so energy, and then CO2. Now remember, we breathe in, our body really likes that Oxygen, and it needs that oxygen to make energy, not necessarily much for this part - the Krebs Cycle, but then we breathe out CO2, that’s the gas that we get rid of.

 

Now our body can use some of that ATP that comes out of the Krebs Cycle but some of that energy goes over to the next step. The next step is where we really need to pump in that oxygen. Ok, so this is the energy again from glycolysis which happens before, um is happening out in the cytoplasm out there and this is where we ended up with NADH, that’s our wagon that we now have filled up with electrons, and we also have ATP, our other source of energy. Those move in, but they move into that inner membrane area, not the matrix but the inner membrane, and they undergo something called the Electron - oh, forgot the oxygen comes in there - the Electron Transport Chain.

 

Basically what’s happening, electrons are getting pushed down the line through a series of reactions along that inner membrane, as they do it opens up channels where ions can go in and out and as that happens you start to reform our energy or our ATP and one more thing. But this requires a lot of energy - the electron transport chain. Some of that energy comes from the Krebs Cycle, some of it comes from ATP and NADH we got from the glycolysis, which happened earlier.

 

Now, out of the Electron Transport Chain, we get more ATP and we get water. There is also some heat released, I mean feel your body, it stays about 98.6 degrees. It stays warm, one of the reasons for that are these reactions that happen in the mitochondria - when they happen they release heat and they release energy and they release water.

 

So we are constantly getting rid of [breathes out] CO2 every time we breathe and we’re losing some water as well and we need to breathe in that oxygen.

 

Now, how much energy do we make from this? So, we’re eating up a plant, we eat the glucose from the plant, our body breaks that down and our mitochondria turns that into energy, here’s what we end up with. So this is a simplified equation for respiration, for cellular respiration.

 

We’ve got C6H12O6, that’s glucose, and then we’ve got oxygen, so six oxygen are needed in this process. Those react together and we release six CO2 molecules, six water molecules, and then we can make anywhere between 36 and 38 ATP - that’s a lot!

 

Basically you’ve taken one glucose molecule, breathed in a little bit of oxygen, and your body, through all of these process makes 36 ATPs! That’s a whole bunch of energy out of one little molecule of glucose. Now our bodies can use that to perform all of the functions that we need need to have. So this is cellular respiration.

 

Now I’ve got two slides here, the same two that you saw before, but again, these are the worksheet things, you can download these, there’s a link down there in the description right below the video. And, if you’re watching this on a computer you’ll see those links pop up, but if you’re looking at this on a phone or any other mobile device, those don’t pop up. For some reason YouTube doesn’t have those annotations allowed there. But if, again if you’re on a computer you’re going to see things popping up all around here, if not, you’re going to see a black screen. But if you go back to the YouTube, my YouTube channel, you’ll see all the same stuff for cellular respiration, including the link down there which will take you to my webpage that’s got all these worksheets on there. And if you’re looking for photosynthesis and Krebs Cycle and ATP / ADP cycle, I’ve got those under the biology link as well.

 

So, good luck and keep on learning!"

 

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Craig Beals  |  Craig@BealsScience.com 

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