1 00:00:00,350 --> 00:00:03,720 - Let's delve into the world of mitochondria 2 00:00:03,720 --> 00:00:07,250 which are probably my favorite organelle. 3 00:00:07,250 --> 00:00:10,090 So let's just have a little review of what mitochondria are 4 00:00:10,090 --> 00:00:11,450 and then we can delve a little bit deeper 5 00:00:11,450 --> 00:00:13,390 into their structure. 6 00:00:13,390 --> 00:00:15,990 So let's just think about a cell 7 00:00:15,990 --> 00:00:18,490 and not just any cell, but a eukaryotic cell. 8 00:00:18,490 --> 00:00:20,120 So that's the cellular membrane 9 00:00:20,120 --> 00:00:23,650 and when people say a eukaryote or a eukaryotic cell 10 00:00:23,650 --> 00:00:27,290 they most typically say, "Oh! That must have its nuclear DNA 11 00:00:27,290 --> 00:00:31,020 "in a membrane-bound nucleus." and that would be true, 12 00:00:31,020 --> 00:00:33,690 so let's draw our membrane-bound nucleus. 13 00:00:33,690 --> 00:00:35,220 That's our nuclear membrane. 14 00:00:35,220 --> 00:00:38,090 You have your DNA in here, 15 00:00:38,090 --> 00:00:39,990 so let's draw some DNA. 16 00:00:39,990 --> 00:00:42,190 But when we talk about eukaryotic cells, 17 00:00:42,190 --> 00:00:44,990 we're not just talking about a membrane-bound nucleus, 18 00:00:44,990 --> 00:00:47,720 we're also talking about other membrane-bound organelles 19 00:00:47,720 --> 00:00:51,180 and in a close second place for a membrane-bound structure 20 00:00:51,180 --> 00:00:52,720 that is very important to the cell 21 00:00:52,720 --> 00:00:55,550 would be the mitochondria. 22 00:00:55,550 --> 00:00:58,890 So let's draw some mitochondria right over here. 23 00:00:58,890 --> 00:01:00,120 So I'll talk a little bit more about 24 00:01:00,120 --> 00:01:02,020 what these little squiggly lines that I'm drawing 25 00:01:02,020 --> 00:01:04,120 inside of the mitochondria are 26 00:01:04,120 --> 00:01:05,290 and this is actually a little bit more 27 00:01:05,290 --> 00:01:06,920 of a textbook visualization, as we'll learn 28 00:01:06,920 --> 00:01:09,450 in a few minutes or seconds that we now have more 29 00:01:09,450 --> 00:01:12,050 sophisticated visualizations of what's actually going on 30 00:01:12,050 --> 00:01:13,690 inside of a mitochondria, but we haven't actually 31 00:01:13,690 --> 00:01:15,250 answered all of our questions, 32 00:01:15,250 --> 00:01:17,150 but you might have already learned that, 33 00:01:17,150 --> 00:01:20,090 so let me make it clear, these are mitochondria. 34 00:01:20,090 --> 00:01:21,020 That's the plural. 35 00:01:21,020 --> 00:01:22,050 If we're just talking about one of them, 36 00:01:22,050 --> 00:01:24,220 we're talking about a mitochondrion. 37 00:01:24,220 --> 00:01:26,120 That's the singular of mitochondria. 38 00:01:26,120 --> 00:01:27,720 But you might have already learned, 39 00:01:27,720 --> 00:01:31,190 some time in your past or in another Khan Academy video, 40 00:01:31,190 --> 00:01:35,960 that these are viewed as the ATP factories for cells. 41 00:01:35,960 --> 00:01:38,750 So let me right it this way. 42 00:01:38,750 --> 00:01:40,990 So ATP factories. 43 00:01:40,990 --> 00:01:45,720 A-T-P factories and if you watched the videos on ATP 44 00:01:45,720 --> 00:01:48,050 or cellular respiration or other videos, 45 00:01:48,050 --> 00:01:51,720 I'd repeatedly talk about how ATP is really the currency 46 00:01:51,720 --> 00:01:55,090 for energy in the cell that when it's in its ATP form 47 00:01:55,090 --> 00:01:57,150 you have adenosine triphosphate. 48 00:01:57,150 --> 00:02:00,150 If you pop one of the phosphate groups off, 49 00:02:00,150 --> 00:02:02,920 you pop one of the P's off, it release energy 50 00:02:02,920 --> 00:02:05,320 and that's what your body uses to do all sort of things 51 00:02:05,320 --> 00:02:08,420 from movement to thinking to all sorts of things 52 00:02:08,420 --> 00:02:10,450 that actually go on in your bodies, 53 00:02:10,450 --> 00:02:12,850 so you can imagine mitochondria are really important 54 00:02:12,850 --> 00:02:16,450 for energy, for when the cell has to do things. 55 00:02:16,450 --> 00:02:18,760 And that's why you'll find more mitochondria 56 00:02:18,760 --> 00:02:21,210 in things like muscle cells, things that have to use 57 00:02:21,210 --> 00:02:22,950 a lot of energy. 58 00:02:22,950 --> 00:02:25,990 Now before I get into the structure of mitochondria, 59 00:02:25,990 --> 00:02:28,590 I wanna talk a little bit about its fascinating past 60 00:02:28,590 --> 00:02:31,550 because we think of cells as the most basic unit of life 61 00:02:31,550 --> 00:02:33,850 and that is true, that comes straight out of cell theory, 62 00:02:33,850 --> 00:02:36,450 but it turns out the most prevalent theory 63 00:02:36,450 --> 00:02:39,620 of how mitochondria got into our cells 64 00:02:39,620 --> 00:02:43,390 is that at one time the predecessors, 65 00:02:43,390 --> 00:02:45,220 the ancestors to our mitochondria, 66 00:02:45,220 --> 00:02:49,790 were free, independent organisms, microorganisms. 67 00:02:49,790 --> 00:02:54,320 So they're descendent from bacterial-like microorganisms 68 00:02:54,320 --> 00:02:57,550 that might have been living on their own 69 00:02:57,550 --> 00:02:59,650 and they were maybe really good at processing energy 70 00:02:59,650 --> 00:03:01,290 or maybe they were even good at other things, 71 00:03:01,290 --> 00:03:04,190 but at some point in the evolutionary past, 72 00:03:04,190 --> 00:03:08,050 they got ingested by what the ancestors of our cells 73 00:03:08,050 --> 00:03:10,510 and instead of just being engulfed and being torn to shreds 74 00:03:10,510 --> 00:03:12,450 and kind of being digested and eaten, 75 00:03:12,450 --> 00:03:15,250 it was like, "Hey, wait, if these things stick around, 76 00:03:15,250 --> 00:03:17,120 "those cells are more likely to survive 77 00:03:17,120 --> 00:03:19,850 "because they're able to help process glucose 78 00:03:19,850 --> 00:03:24,550 "or help generate more energy out of things." 79 00:03:24,550 --> 00:03:27,920 And so the cells that were able to kind of live 80 00:03:27,920 --> 00:03:30,320 in symbiosis have them kind of give a place 81 00:03:30,320 --> 00:03:33,190 for the mitochondria to live or the pre-mitochondria, 82 00:03:33,190 --> 00:03:35,490 the ancestor mitochondria, those survived 83 00:03:35,490 --> 00:03:38,990 and then through kind of the processes of natural selection, 84 00:03:38,990 --> 00:03:41,350 this is what we now associate, 85 00:03:41,350 --> 00:03:43,290 we now associate eukaryotic cells 86 00:03:43,290 --> 00:03:44,890 as having mitochondria, 87 00:03:44,890 --> 00:03:47,820 so I find this whole idea of one organism being inside 88 00:03:47,820 --> 00:03:52,090 of another organism in symbiosis even at the cellular level, 89 00:03:52,090 --> 00:03:55,350 that's kind of mind-boggling, but anyway, 90 00:03:55,350 --> 00:03:57,590 I'll stop talking about that and now let's just talk 91 00:03:57,590 --> 00:03:59,850 about the present, let's talk about 92 00:03:59,850 --> 00:04:03,220 what the actual structure of mitochondria are. 93 00:04:03,220 --> 00:04:06,120 And I'll first draw kind of a simplified drawing 94 00:04:06,120 --> 00:04:10,050 of a mitochondion and I'll draw a cross section. 95 00:04:10,050 --> 00:04:13,120 So, I'm gonna draw a cross section. 96 00:04:13,120 --> 00:04:15,590 So if we were to kind of cut it in half. 97 00:04:15,590 --> 00:04:16,990 So what I've drawn right over here 98 00:04:16,990 --> 00:04:18,720 this would be its outer membrane. 99 00:04:18,720 --> 00:04:24,190 This is the outer membrane right over here 100 00:04:24,190 --> 00:04:25,520 and we label that. 101 00:04:25,520 --> 00:04:28,390 Outer membrane. 102 00:04:28,390 --> 00:04:30,588 And all of these membranes that I'm gonna draw, 103 00:04:30,588 --> 00:04:34,250 they're all going to be phospholipid bilayers. 104 00:04:34,250 --> 00:04:38,550 So if I were to zoom in right over here, 105 00:04:38,550 --> 00:04:41,420 so let me, if I were to zoom in, 106 00:04:41,420 --> 00:04:44,390 we would see a bilayer of phospholipids. 107 00:04:44,390 --> 00:04:47,350 So you have your 108 00:04:47,350 --> 00:04:50,490 hydrophilic heads facing outwards, 109 00:04:50,490 --> 00:04:53,390 hydrophilic heads facing outwards 110 00:04:53,390 --> 00:04:57,050 and your hydrophobic tails facing inwards. 111 00:04:57,050 --> 00:04:59,200 So. 112 00:05:00,090 --> 00:05:02,250 You see something just like that, 113 00:05:02,250 --> 00:05:05,880 so they're all phospholipid bilayers. 114 00:05:05,880 --> 00:05:07,890 But they aren't just phospholipids. 115 00:05:07,890 --> 00:05:10,220 All of these membranes have all sorts of proteins imbedded, 116 00:05:10,220 --> 00:05:13,250 I mean cells are incredibly complex structures, 117 00:05:13,250 --> 00:05:16,890 but even organelles like mitochondria have a fascinating, 118 00:05:16,890 --> 00:05:18,690 I guess you would say sub-structure to them. 119 00:05:18,690 --> 00:05:21,120 They themselves have all sorts of interesting proteins, 120 00:05:21,120 --> 00:05:23,150 enzymes imbedded in their membranes 121 00:05:23,150 --> 00:05:25,450 and are able to help regulate what's going on 122 00:05:25,450 --> 00:05:28,490 inside and outside of these organelles. 123 00:05:28,490 --> 00:05:34,760 And one of the proteins that you have in the outer membrane 124 00:05:34,760 --> 00:05:38,612 of mitochondria, they're called porins 125 00:05:38,612 --> 00:05:40,390 and porins aren't found only in mitochondria, 126 00:05:40,390 --> 00:05:41,590 but they're kind of tunnel proteins, 127 00:05:41,590 --> 00:05:44,450 they're structured so they kind of form a hole 128 00:05:44,450 --> 00:05:46,550 in the outer membrane. 129 00:05:46,550 --> 00:05:49,350 So I'm drawing them the best that I can. 130 00:05:49,350 --> 00:05:51,080 These are porins 131 00:05:51,080 --> 00:05:54,320 and what's interesting about porins is they don't allow 132 00:05:54,320 --> 00:05:57,120 large molecules to pass through passively, 133 00:05:57,120 --> 00:06:02,050 but small molecules like sugars or ions can pass passively 134 00:06:02,050 --> 00:06:04,090 through the porins. 135 00:06:04,090 --> 00:06:06,120 And so, because of that, your ion concentration 136 00:06:06,120 --> 00:06:07,450 and well, I should actually say, 137 00:06:07,450 --> 00:06:09,085 your small molecule concentrations tend 138 00:06:09,085 --> 00:06:12,555 to be similar on either side of this membrane, 139 00:06:12,555 --> 00:06:15,085 on either side of this outer membrane. 140 00:06:15,085 --> 00:06:17,125 But that's not the only membrane involved 141 00:06:17,125 --> 00:06:18,845 in a mitochondrion. 142 00:06:18,845 --> 00:06:20,685 We also have a inner membrane. 143 00:06:20,685 --> 00:06:22,605 I'll do that in yellow. 144 00:06:22,955 --> 00:06:24,155 We also have a inner membrane 145 00:06:24,155 --> 00:06:27,285 and I'm gonna draw it with a textbook model first 146 00:06:27,285 --> 00:06:28,545 and then we'll talk a little bit about, 147 00:06:28,545 --> 00:06:32,885 since we think this model is not quite right, 148 00:06:32,885 --> 00:06:36,685 but in this, so we have this inner membrane, 149 00:06:36,685 --> 00:06:41,625 inner membrane, 150 00:06:41,625 --> 00:06:45,525 and this inner membrane has these folds in it 151 00:06:45,525 --> 00:06:46,985 to increase their surface area 152 00:06:46,985 --> 00:06:48,555 and the surface area is really important 153 00:06:48,555 --> 00:06:50,485 for the inner membrane because that's 154 00:06:50,485 --> 00:06:53,355 where the processes of the electron transport chain 155 00:06:53,355 --> 00:06:55,955 occur across, essentially, these membranes. 156 00:06:55,955 --> 00:06:57,385 So you want this extra surgace area 157 00:06:57,385 --> 00:07:00,685 so you can essentially have more of that going on. 158 00:07:00,685 --> 00:07:02,585 And these folds have a name. 159 00:07:02,585 --> 00:07:04,225 So if you're talking about one of them, 160 00:07:04,225 --> 00:07:05,725 if you're talking about one of these folds, 161 00:07:05,725 --> 00:07:10,005 you're talking about a crista, 162 00:07:10,005 --> 00:07:14,485 but if you're talking about more than one of them, 163 00:07:14,485 --> 00:07:18,555 you would call that a cristae, cristae. 164 00:07:18,555 --> 00:07:20,085 Sometimes I've seen the pronunciation of this 165 00:07:20,085 --> 00:07:24,525 as cristae, cristae or cristae, that's plural for crista. 166 00:07:24,525 --> 00:07:27,925 These are just folds in the inner membrane 167 00:07:27,925 --> 00:07:30,125 and once again the inner membrane is also 168 00:07:30,125 --> 00:07:33,655 a phospholipid bilayer. 169 00:07:33,655 --> 00:07:36,085 Now inside of the inner membranes, 170 00:07:36,085 --> 00:07:40,085 so between the outer membrane and the inner membrane 171 00:07:40,085 --> 00:07:42,985 you could imagine what this is gonna be called. 172 00:07:42,985 --> 00:07:46,485 That space is called the intermembrane space, 173 00:07:46,485 --> 00:07:51,885 not too creative of a name, intermembrane space 174 00:07:51,885 --> 00:07:53,885 and because of the porins, 175 00:07:53,885 --> 00:07:56,545 the small molecule concentration 176 00:07:56,545 --> 00:07:58,985 of the intermembrane space and then outside 177 00:07:58,985 --> 00:08:02,685 of the mitochondria, 178 00:08:02,685 --> 00:08:03,855 out in the cytosol, 179 00:08:03,855 --> 00:08:05,825 those concentrations are gonna be similar, 180 00:08:05,825 --> 00:08:08,585 but then the inner membrane does not have the porins 181 00:08:08,585 --> 00:08:11,425 in it and so you can actually have a different concentration 182 00:08:11,425 --> 00:08:12,655 on either side and that is essential 183 00:08:12,655 --> 00:08:14,625 for the electron transport chain. 184 00:08:14,625 --> 00:08:16,555 The electron transport chain really culminates 185 00:08:16,555 --> 00:08:19,055 with hydrogen, a hydrogen ion gradient 186 00:08:19,055 --> 00:08:20,785 being built between the two sides 187 00:08:20,785 --> 00:08:24,085 and then they flow down that gradient through a protein 188 00:08:24,085 --> 00:08:28,125 called ATP synthase which helps us synthesize ATB, 189 00:08:28,125 --> 00:08:29,925 but we'll talk more about that maybe in this video 190 00:08:29,925 --> 00:08:31,255 or in a future video, 191 00:08:31,255 --> 00:08:33,255 but let's finish talking about the different parts 192 00:08:33,255 --> 00:08:36,555 of a mitochondrion. 193 00:08:36,555 --> 00:08:40,125 So inside the inner membrane you have 194 00:08:40,125 --> 00:08:42,855 this area right over here is called the matrix. 195 00:08:42,855 --> 00:08:45,685 It's called, let me use this in a different color, 196 00:08:45,685 --> 00:08:47,875 this is 197 00:08:48,555 --> 00:08:49,385 the matrix 198 00:08:49,385 --> 00:08:50,955 and it's called the matrix 'cause it actually has 199 00:08:50,955 --> 00:08:53,225 a much higher protein concentration, 200 00:08:53,225 --> 00:08:58,085 it's actually more viscus than the cytosol 201 00:08:58,085 --> 00:09:02,185 that would be outside of the 202 00:09:03,675 --> 00:09:05,385 mitochondria. 203 00:09:05,385 --> 00:09:07,525 So this right over here is the matrix. 204 00:09:07,525 --> 00:09:09,815 When we we talk about cellular respiration, 205 00:09:09,815 --> 00:09:11,925 cellular respiration has many phases in it. 206 00:09:11,925 --> 00:09:13,345 We talk about glycolysis. 207 00:09:13,345 --> 00:09:15,955 Glycolysis is actually occurring in the cytosol. 208 00:09:15,955 --> 00:09:20,315 So glycolysis can occur in the cytosol. 209 00:09:20,315 --> 00:09:22,855 Glycolysis. 210 00:09:22,855 --> 00:09:26,025 But the other major phases of cellular respiration. 211 00:09:26,025 --> 00:09:28,055 Remember we talk about the citric acid cycle 212 00:09:28,055 --> 00:09:29,855 also known as the Krebs cycle, 213 00:09:29,855 --> 00:09:32,585 that is occuring in the matrix. 214 00:09:32,585 --> 00:09:35,825 So Krebs cycle 215 00:09:35,825 --> 00:09:37,225 is occuring in the matrix 216 00:09:37,225 --> 00:09:40,525 and then I said the electron transport chain 217 00:09:40,525 --> 00:09:42,155 which is really what's responsible for producing 218 00:09:42,155 --> 00:09:46,185 the bulk of the ATP, that is happening through proteins 219 00:09:46,185 --> 00:09:49,255 that are straddling the inner membrane 220 00:09:49,255 --> 00:09:55,125 or straddling the cristae right over here. 221 00:09:55,125 --> 00:09:56,855 Now we're just done. 222 00:09:56,855 --> 00:09:59,085 Probably one of the most fascinating parts of mitochondria, 223 00:09:59,085 --> 00:10:01,985 we said that we think that they are descendent 224 00:10:01,985 --> 00:10:04,725 from these ancient independent lifeforms 225 00:10:04,725 --> 00:10:06,825 and in order to be an ancient independent life form, 226 00:10:06,825 --> 00:10:09,055 they'd would have to have some information, 227 00:10:09,055 --> 00:10:13,655 some way to actually transmit their genetic information 228 00:10:13,655 --> 00:10:16,185 and, it turns out, mitochondria actually have 229 00:10:16,185 --> 00:10:18,085 their own genetic information. 230 00:10:18,085 --> 00:10:19,785 They have mitochondrial DNA 231 00:10:19,785 --> 00:10:21,785 and they often don't just even have one copy of it, 232 00:10:21,785 --> 00:10:23,415 they have multiple copies of it 233 00:10:23,415 --> 00:10:28,225 and they're in loops very similar to bacterial DNA. 234 00:10:28,225 --> 00:10:29,585 In fact, they have a lot in common 235 00:10:29,585 --> 00:10:30,855 with bacterial DNA and that's why we think 236 00:10:30,855 --> 00:10:34,385 that the ancestor to mitochondria that live independently 237 00:10:34,385 --> 00:10:38,655 was probably a form of bacteria or related to bacteria 238 00:10:38,655 --> 00:10:39,985 in some way. 239 00:10:39,985 --> 00:10:41,485 So this is, this right over there, 240 00:10:41,485 --> 00:10:43,885 that is the loop of mitochondrial DNA. 241 00:10:43,885 --> 00:10:46,555 So all the DNA that's inside of you, the bulk of it, 242 00:10:46,555 --> 00:10:50,385 yes, it is in your nuclear DNA, but you still have 243 00:10:50,385 --> 00:10:52,625 a little bit of DNA in your mitochondria 244 00:10:52,625 --> 00:10:55,615 and what's interesting is your mitochondrial DNA, 245 00:10:55,615 --> 00:10:59,455 your mitochondria, are inherited, essentially, 246 00:10:59,455 --> 00:11:03,275 from your mother's side, because when a egg is fertilized, 247 00:11:05,545 --> 00:11:08,825 a human egg has tons of mitochondria in it 248 00:11:09,615 --> 00:11:11,785 and I'm obviously not drawing all of the things 249 00:11:11,785 --> 00:11:12,825 in the human egg. 250 00:11:12,825 --> 00:11:14,285 It obviously has a nucleus and all of that. 251 00:11:14,285 --> 00:11:16,355 The sperm has some mitochondria in it, 252 00:11:17,985 --> 00:11:20,467 you could imagine it needs to be able 253 00:11:20,467 --> 00:11:22,325 to win that very competitive fight 254 00:11:22,325 --> 00:11:24,125 to get to fertilize the egg, 255 00:11:24,125 --> 00:11:26,355 but the current theory is all or most of that 256 00:11:26,355 --> 00:11:30,085 gets digested or dissolved once it actually gets 257 00:11:30,085 --> 00:11:31,525 into the egg. 258 00:11:31,525 --> 00:11:34,485 And anyway, the egg itself has way more mitochondria, 259 00:11:34,485 --> 00:11:38,755 so the DNA in your mitochondria is 260 00:11:38,755 --> 00:11:42,085 from your mother or is essentially from your mother's side 261 00:11:42,085 --> 00:11:43,655 and that's actually used, mitochondrial DNA, 262 00:11:43,655 --> 00:11:45,585 when people talk about kind of an ancient Eve 263 00:11:45,585 --> 00:11:47,425 or tracing back to having kind 264 00:11:47,425 --> 00:11:48,625 of one common mother, 265 00:11:48,625 --> 00:11:52,885 people are looking at the mitochondrial DNA, 266 00:11:52,885 --> 00:11:56,785 so it is actually quite, quite fascinating. 267 00:11:56,785 --> 00:11:58,725 Now I said a little bit earlier, 268 00:11:58,725 --> 00:12:00,855 and you know, obviously, it has its own DNA 269 00:12:00,855 --> 00:12:02,345 and then because it has its own DNA 270 00:12:02,345 --> 00:12:04,455 it's able to synthesize some of its own RNA, 271 00:12:04,455 --> 00:12:07,555 its own ribosomes, so it also has ribosomes here. 272 00:12:07,555 --> 00:12:10,455 But it doesn't synthesize all of the proteins 273 00:12:10,455 --> 00:12:11,725 that are sitting in mitochondria. 274 00:12:11,725 --> 00:12:14,385 A lot of those are still synthesized by 275 00:12:14,385 --> 00:12:17,455 or encoded for by your nuclear DNA 276 00:12:17,455 --> 00:12:19,955 and are actually synthesized outside of the mitochondria 277 00:12:19,955 --> 00:12:22,885 and then make their way into the mitochondria, 278 00:12:22,885 --> 00:12:25,855 but mitochondria are these fascinating, fascinating things. 279 00:12:25,855 --> 00:12:29,455 They're these little creatures living in symbiosis 280 00:12:29,455 --> 00:12:32,355 in our cells and they're able to replicate themselves 281 00:12:32,355 --> 00:12:34,685 and I don't know, I find all of this mind boggling. 282 00:12:34,685 --> 00:12:35,385 But anyway. 283 00:12:35,385 --> 00:12:37,785 I said that this was the textbook model 284 00:12:37,785 --> 00:12:39,725 because it turns out, when you look 285 00:12:39,725 --> 00:12:43,685 at a micrograph, a picture of mitochondria, 286 00:12:43,685 --> 00:12:45,485 it seems to back up this textbook model 287 00:12:45,485 --> 00:12:49,125 of these folds, these cristae just kind of folding in, 288 00:12:49,125 --> 00:12:51,755 but when we've been able to have more sophisticated 289 00:12:51,755 --> 00:12:53,645 visualizations it actually turns out 290 00:12:53,645 --> 00:12:55,985 that it's not just these simple folds 291 00:12:55,985 --> 00:12:59,055 that the inner membrane essentially hooks 292 00:12:59,055 --> 00:13:02,255 into the matrix and it turns out it has 293 00:13:02,255 --> 00:13:05,085 these little tunnels that connect the space 294 00:13:05,085 --> 00:13:10,525 inside of the cristae to the intermembrane space. 295 00:13:10,525 --> 00:13:12,825 So I like to think about this because it makes you realize, 296 00:13:12,825 --> 00:13:14,825 you know, we look in textbooks and we take these things 297 00:13:14,825 --> 00:13:17,325 like mitochondria for granted, like, "Oh yeah, of course. 298 00:13:17,325 --> 00:13:18,875 "That's where ATP factories are," 299 00:13:18,875 --> 00:13:21,685 but it's still an area for visualization research 300 00:13:21,685 --> 00:13:24,455 to fully understand exactly how they work 301 00:13:24,455 --> 00:13:25,855 and even how they are structured 302 00:13:25,855 --> 00:13:28,655 that this Baffle Model where you see these cristae 303 00:13:28,655 --> 00:13:31,225 kind of just coming in and out of the different sides. 304 00:13:31,225 --> 00:13:33,885 This is actually no longer the accepted model 305 00:13:33,885 --> 00:13:36,745 for the actual visualization, the structure of mitochondria. 306 00:13:36,745 --> 00:13:39,485 Something more like this, something more where 307 00:13:39,485 --> 00:13:42,315 you have this cristae junction model 308 00:13:42,315 --> 00:13:46,615 where you have, if I were to draw a cross section 309 00:13:46,615 --> 00:13:50,025 where this is the, 310 00:13:50,025 --> 00:13:52,255 I drew the outer membrane and the inner membrane, 311 00:13:52,255 --> 00:13:54,655 I'll just draw has these little tunnels 312 00:13:54,655 --> 00:13:59,535 to the actual space inside of the cristae. 313 00:13:59,535 --> 00:14:03,455 This is actually now the more accepted visualization, 314 00:14:03,455 --> 00:14:04,725 so I want you to appreciate 315 00:14:04,725 --> 00:14:06,885 that when in Biology, you read something in a textbook 316 00:14:06,885 --> 00:14:08,225 you kind of say, "Oh, people have figured all 317 00:14:08,225 --> 00:14:10,285 "of this stuff out," but people are still think about, 318 00:14:10,285 --> 00:14:11,625 "Well, how does this structure work? 319 00:14:11,625 --> 00:14:12,785 "What is the actual structure?" and then, 320 00:14:12,785 --> 00:14:14,825 "How does it actually let this organelle, 321 00:14:14,825 --> 00:14:16,755 "this fascinating organelle do all of the things 322 00:14:16,755 --> 00:14:18,805 "that it needs to do?"