0:00 Armondo Houserinan biology and medicine videos, please make sure to subscribe, 0:05 join the form 0:06 and group for the latest videos, please visit Facebook Armondo Houserinan. 0:12 In this video, we're going to look at the fates of a cell. 0:16 So here we have a mitotic cell, such as the cells in our skin, in our gut, and 0:23 in test 0:24 time, the epithelial cells. 0:27 These mitotic cells will double its organelles, it will double its DNA, and 0:32 then it will divide 0:33 into two identical cells. 0:36 So this is known as a cell cycle. 0:38 You have the G1 phase, the S phase, the G2 phase, and the M phase. 0:46 So this is the cell cycle where the cell divides. 0:51 But the mitotic cell can also enter a G0 phase where it will essentially, which 0:59 is essentially 0:59 cell arrest. 1:01 And so this is known as the G0 phase, the dormant phase. 1:05 But with appropriate signals, the cell can re-enter the cell cycle if needed to 1:11 regenerate or renew 1:13 the cells around it. 1:19 Of course, after this mitotic cell has divided many, many times, it will reach 1:24 a limit to 1:25 when it cannot divide anymore. 1:28 And so this cell will become a senescent cell. 1:30 So a senescent cell means that the cell cannot replicate anymore because it has 1:37 reached its 1:37 limit, known as the hayflic limit. 1:41 One reason for this is that its DNA becomes shorter with each replication. 1:47 So if this was the cells DNA, so if this was the end of the cells DNA, the end 1:57 of the DNA 1:59 actually becomes shorter with each replication. 2:02 The ends of the DNA are known as telomeres. 2:07 So if the ends of the DNA does not become shorter, it would mean that we would 2:14 be immortal. 2:16 And interestingly enough, cancer cells are immortal because their DNA do not 2:21 get shorter 2:22 like that, like normal cells. 2:31 Now not all cells are mitotic cells. 2:35 Remember mitotic cells are like your skin cells, your gut and intestine cells. 2:41 But then you have post mitotic cells, which are cells such as your neurons and 2:46 your muscle 2:47 cells. 2:48 These cells cannot enter the cell cycle. 2:53 Once it's become that type of cell, it cannot divide. 2:56 It just becomes dormant, you can say. 3:00 It will stay in the G0 phase constantly. 3:05 Anyways, that's important to know that you have mitotic cells and post mitotic 3:10 cells. 3:11 But also you have also germ cells, which are your sperm and your eggs. 3:16 Anyway, so these cells, any cells can actually undergo a few fates during its 3:26 course. 3:27 They can undergo apoptosis, necrosis and oto-fagie. 3:36 Now let's look at each one of these three and look at what they're all about. 3:43 So apoptosis is essentially a programmed cell death. 3:48 It's a normal physiological response, which removes unwanted cells. 3:53 It's programmed cell death. 3:55 It is due to some stress that occurs to a cell. 3:59 It can be an infection or whatever. 4:02 But the cell realizes this and it will undergo programmed cell death, apoptosis 4:08 . 4:08 In apoptosis, the cell receives a death signal, either from the outside or from 4:13 within the 4:14 cell. 4:15 This death signal causes the breakdown of the cell's DNA and the cytoskeleton 4:22 and proteins, 4:23 which causes the cell to shrink. 4:26 As the cell shrinks, blebs will form. 4:30 These are like droplets of water separating and at the same time, the nucleus 4:36 breaks. 4:37 But the cell's integrity is still maintained. 4:41 It doesn't go everywhere. 4:43 As blebs are formed, it will form into apoptotic bodies. 4:49 These apoptotic bodies will have the cell's organelles and parts within it 4:56 confined. 4:57 Then macrophages will come along and clean up the apoptotic bodies. 5:01 So the apoptotic bodies are phagostitis. 5:05 This leads to a silent, non-inflammatory cell death and everything is cleaned 5:13 up. 5:14 Necrosis on the other hand is completely different. 5:17 The cell may be chemically or physically damaged by some form of trauma or 5:22 infection. 5:24 A normal cell, if it was in normal conditions, it will undergo apoptosis. 5:29 But if a cell just died, it will undergo necrosis, and so it will die by non- 5:36 programmed means. 5:39 Necrosis is non-programmed cell death. 5:42 And what happens here is that the cell will swell. 5:46 Not only this, but the organelles will swell too and it will accumulate, just 5:51 keep accumulating 5:52 water. 5:53 And this process continues. 5:56 The cells will also show signs of blubbing as though it will separate. 6:01 But in reality, it will just grow and then rupture and break the out and it 6:06 will break 6:07 the outer cell membrane, releasing all its cellular content to adjacent cells, 6:14 causing 6:15 further damage. 6:18 This will create a response that will attract neutrophils, which are highly 6:22 inflammatory 6:22 cells, to clean up the mess and cause further inflammation. 6:27 Therefore, we can say that necrosis, unlike apoptosis, causes the whole cell to 6:34 rupture 6:35 and therefore it is highly inflammatory. 6:39 Cells can also undergo otophagy. 6:42 This is where, within the cell, you have damaged organelles, specifically. 6:49 So the cell itself is not damaged, just the organelles within it is damaged, 6:54 either through 6:55 starvation or infection. 6:58 If this happens, the cell does not want to keep this organelle, and so it will 7:03 undergo 7:04 otophagy. 7:07 What happens here is that the cell normally have lysosomes, which are vesicles 7:11 containing 7:11 an acidic environment. 7:14 The cell will program the lysosomes to engulf the damaged organelle, or, if it 7:19 was an infectious 7:20 agent, to engulf the infectious agent, and whatever it is. 7:26 And then it will essentially, the lysosome will essentially digest it. 7:30 And so through this mechanism, the cell will survive and will not need to 7:35 undergo apoptosis. 7:36 It's balanced, its energy balance is maintained, and it can remove the 7:42 infection, or it can 7:44 eliminate the damaged organelle, whatever the case may be. 7:48 So that was a brief overview of the fates of the cell. 7:52 They can die either through apoptosis or necrosis, and they can undergo otoph 7:56 agy.
