Endomembrane System: Protein Secretion

in this video, we're going to begin our introduction to the Endo Membrane System and toe one of the major functions of the Indo membrane system, which is protein secretion. And so the endo membrane system can be defined as a group of membrane bound organelles that are inside of a eukaryotic cell. And so the root endo and endo membrane system means inside and so you can see that we're talking about membranes that were found on the inside of the South, and the system here is really just referring to the fact that it's made up of a group of organelles. And all of these organelles are membrane bound meeting that their boundaries are made up of membranes. Now the endo membrane system includes many different organelles that we're going to mention down below. In this table. However, all of these organelles that air part of the endo membrane systems are interconnected to each other by these structures that air called vesicles and so vesicles is just a fancy name for these tiny little membrane bubbles that can carry materials on the inside. And so all of these organelles that are part of the end of membrane system they are interconnected by these vesicles, and we'll get to see examples of vesicles as we move forward. In our course now, the end of monitoring system has ah lot of different functions. It has multiple functions and we're not going to talk about. All of the different functions were mainly going to focus on two of its functions, and those include protein secretion as well as cellular digestion. And so notice that down below. In our example here we have a table that shows the organelles of the endo membrane system and notice that behind them we have this green color coding that links, uh, the organelles that we're gonna talk about in our course moving forward that are involved with protein secretion. And then I noticed that in yellow we have the organize that are involved with cellular digestion, that we're gonna talk about moving forward in our course, and then over here with this white background, we have the cell membrane, which we're not going to focus on in this particular portion of our lesson. We'll talk Maura about cell membranes later in a different lesson, However, what you'll see is that all of these numbers that you see here are showing you organelles that are part of the end of membrane system, and we have them grouped based on their functions, whether they're involved with protein secretion or cellular digestion. So moving forward in our course, we're gonna focus mainly on the organelles that are involved with protein secretion, which include the nuclear envelope or the nucleus of the eukaryotic self. The end of plasmid ridiculous, um, of the eukaryotic self, the Golgi apparatus, as well as transport vesicles, which we mentioned again are these little membrane bubbles. And then later in our course, we'll get to talk more about the organizer of the remembering system that are involved in cellular digestion, which include the license soames and paroxysms as well as vac. You'll, uh, such a central vacuole is and things like that. And so this here really just eyes outlining Theo organelles of the end of membrane system and grouping them by their functions. And we'll get to talk Maura about each of these organelles that are on here as we move forward in our course. So that being said, I'll see you all in our next video

So from our last lesson video, we know that one of the major functions of the Endo membrane system is protein secretion. But what exactly does protein secretion even mean? Well, the words secretion is just a fancy name for a process by which a substance is released into the environment or released into the surroundings of the cell. And so protein secretion is a process by which a protein is being released into the environment or released into the surroundings of the cell. And so protein secretion involves several different organ al's that interact with each other in a very specific order. And so moving forward in our course, we're going to talk about each of the organelles that air involved with protein secretion. And so here we're showing you an image of these organelles, but moving forward in our course, we're going to talk about each of the organelles in their own separate videos. And so this includes the nucleus of the cell as well as the Endo Plas, Mick, ridiculous, um, and the Golgi apparatus that we see here. And so once again, we'll get to talk about each of these organelles moving forward in our course in their own separate video. So I'll see you all in our next video

in this video, we're going to talk about the first organ L of the Endo Membrane system, which is the nucleus, and so protein secretion is going to start in the nucleus. And this is because the nucleus of a eukaryotic cell stores the D N A of the cell and recall that the D N A of the cell carries the recipe or the code for making the protein. And so that's exactly why protein secretion starts in the nucleus, because you can't secrete the protein until after you've made the protein. Now the nucleus can be defined as a rounded structure that contains and protects most of a eukaryotic cells. D n A. Now there are these three structures that we're going to talk about, uh, in the nucleus that you all should be aware of. Now remember that the nucleus is part of the Endo membrane system, which means that its border is going to be a membrane itself, and the border of the nucleus has a specific name that we refer to as the nuclear envelope. And so the nuclear envelope is really just defining the double membrane barrier that surrounds the nucleus and again acts as the barrier of the nucleus, basically separating the inside of the nucleus from the outside of the nucleus. Now nuclear pores are referring to tiny little pores or holes that are found in the nuclear envelope. And these tiny little nuclear pores or holes in the nuclear envelope are going to allow the entry and exit into and out of the nucleus so they basically can control and monitor what leaves the nucleus and also what enters the nucleus. Now this other, uh, word here the nuclear Olis is referring to a small, dense structure that's on the inside of the nucleus. And this is specifically where rhizomes are assembled and recall from our previous lesson videos that ribosomes are important for making proteins, which is another reason why the nucleus is the first step of protein secretion because it is involved with making ribosomes. And so let's take a look at our image down below right here to get a better understanding of the eukaryotic nucleus. So over here on the left hand side, we're showing you our representation of the Eukaryotic cell and notice right here. We're showing you the nucleus of the cell, and so if we zoom in here to the nucleus of the cell, which will notice is that it is made up of a membrane, a double membrane, and this double membrane that you see here acts as the barrier of the nucleus. And so the gray structures that you see here are referring to the nuclear envelope. And so we can label this as the nuclear envelope, the double membrane that surrounds the nucleus and acts as its barrier. Basically, what you see surrounding the nucleus here. Now, notice that in the nuclear envelope there are these holes that you see throughout these pores, if you will, the nuclear pores. So this whole that you see right here in the nuclear envelope is referring to the nuclear pore. Now, notice that on the inside of the nucleus we have d n A. And so these structures that you see here represent DNA and the DNA. Most of the Eukaryotic cell's DNA is found inside of the nucleus, so that's important to keep in mind now, also within the nucleus right here at the core of the nucleus. There's another small, dense structure on the inside of the nucleus, and this is where ribosomes are going to be assembled. So this is specifically the new CLee Olis. So this is the nuclear Alissa structure within the inside of the nucleus itself that is involved with building or assembling rhizomes. Now, the reason, once again that, uh, the protein secretion process starts in the nucleus is because the nucleus is what is going to contain the d n a of the cell. And so the DNA of a cell which is again found in the nucleus of the cell, is going to be transcribed into RNA, and then the RNA will then be translated into a protein itself. And, uh, the protein recall is being built by the Riva Zone. And there's gonna be a lot more details on this process that we're mentioning right here. Later, in our course on, we'll talk more about this idea of transcription or being transcribed as well as translation again later in our course. For now, what you should note is that protein secretion starts in the nucleus because in order for a protein to be made, it first needs the DNA in the nucleus needs to be transcribed into RNA, and then the Arna needs to be translated into the protein, and then once the protein is made, it can then be secreted. And so this year concludes our introduction to the nucleus, and we'll be able to talk more about the other organelles at the end of membrane system moving forward in our course. So I'll see you guys in our next video.

Which part of the nucleus is responsible for assembling ribosomes and ribosomal RNA?

• A. The mitochondria.
• B. Nuclear Envelope.
• C. Nuclear pores.
• D. Nucleolus.

in this video, we're going to talk about the second organ l of the Endo membrane system, which is the Endo Plas Mick. Ridiculous. Um, now the Endo Plas Mick ridiculous is commonly abbreviated as just e. R for short. And so the end of plasmid particular amore. The e r uh, is a part of the Endo membrane system, which means that its boundary is going to be a membrane. And so it's no surprise that the Endo Plasvic ridiculous is going to be a membrane ISS structure. Now the end of plasma particular more. Er it is a membrane is structure, but it's actually continuous with the nuclear envelope, which is the membrane of the nucleus. And, uh, the end of plasma ridiculous is actually going to have multiple functions, and we'll be able to talk about some of those functions down below here now, because the end of plasma ridiculous is a membrane structure, the membrane structure is going to act as a barrier to the end of plasma ridiculous separating the outside of the end of plasma ridiculous, um, from the inside of the end of plasma ridiculous and the internal space or the internal compartment of the end of Plasvic. Ridiculous has a specific name that we call the e. R. Lumen. And so the er Lumen is again the internal space or compartment on the inside of the Indo plasma particular. Now, really, there are two main types of endo plasmid particular, um, that you all should know and we have them number down below number one and number two. And so the first type of end a plasma particular, um, that you should know is the rough endo plasmid particular, um, or the rough e r for short And the rough er is sometimes abbreviated as just the r e r for the rough end A plasma critical. Um, now the rough end A plasma particular, um, or the rough e r r e r is going to be a lot closer to the nucleus. So it directly extends off of the nuclear envelope. And as its name implies here with rough the rough end of plasmid particular, um, has a rough surface that is coded with ribosomes. And so the reason the rough er is called the rough ER is because its surface is rough, or at least it appears to be rough because it has ribosomes coating the surface and attached to the surface of the ER. The rough er itself now recall that ribosomes are structures that build proteins. And so these ribosomes that air coded to the surface or attached to the surface of the rough er, are going to build a newly built proteins. Uh, build newly built proteins, and the newly built proteins that are built by these rhizomes coded on the surface of the rough er are going to fold and get modified on the rough E r. Lumen or the internal space or compartment of the rough end. A plasma Ridiculous. Now, the second type of endo plasvic ridiculous that you all should know is the smooth e r. Or for short the S e r for smooth and a plasmid ridiculous. And the smooth and a plasma ridiculous or s er is farther away from the nucleus, so it's extending off of the membrane of the rough er itself. And as its name implies, with the smooth, the smooth er has a smooth surface on. That is because it has a rib, a zone free surface, meaning that there are no ribosomes on the surface of the smooth er Now because the smooth yard does not have any ribosomes, it's Rabies, Um, free. Then it's not going to be associated with building proteins. Instead, the smooth er is going to be building or synthesizing lipids, and it's also important for detoxifying drugs and poisons. So let's take a look at our example. Image down below to further distinguish between the rough e r and the smooth E r. So once again, on the left hand side, over here, we're showing you are eukaryotic cell representation and we're zooming in specifically into this region right here, uh, in this box. And so what you'll notice is the nucleus, which we already covered in our last lesson. Video is right here in this image. This is the nucleus, and the nucleus we know is part of the end of membrane system because it has a membrane, uh, surrounding it called the nuclear envelope and the end of plasma ridiculous, which is shown here in blue and an orange eyes really just a continuous extension from the nuclear envelope, as we mentioned up above its continuous with the nuclear envelope. Now there's two types of endo plasma ridiculous. We know that there's the rough end. A plasma ridiculous, um, and the smooth and a plasma ridiculous. The rough endo Plasvic ridiculous is closer to the nucleus. And so the rough end of plasma ridiculous here is in bluish color Here it's in the bluish color surrounding the nucleus. And so we could go ahead and label this as the rough endo plasmid ridiculous or the rough e r. Now recall that the rough er is rough because it has a rough surface that is coded with ride his own. So it has a rough ride, his own coated surface. So when we take a look down below notice that all of these little blue dots that we see here on the rough er represent Riva zones okay, including this little dot right here. Those are ribosomes. And remember, the ribosomes are important for building proteins. And so, uh, the newly built proteins that are made, they're actually going to fold and get modified on the inside of the rough end. A plasmid particular inside of the lumen of the plasma. Ridiculous. And so, uh, if these Riva zones here, these little blue dots, if they're making proteins those proteins will end up on the inside of the endo Klasnic. Ridiculous, um, or the Lumet now extending off of the membrane of the rough er, we have this reddish structure that we're showing you here, which is actually the smooth er or the S E r. And so we could go ahead and label this as the smooth e r the smooth and a plasma ridiculous. And notice that the surface of the smooth and a plasma critical, um looks pretty smooth because it does not have any ribosomes. It's free. It's rivals, um, free. And so instead of making proteins, it's gonna be important for making lipids and detoxifying drugs and poisons and so extending off of these, uh, endo plasmid particularly because they're made up of membranes. Thes little membrane bubbles are capable of forming from both the smooth er uh, as well as from the rough er to even though we're not showing you any membrane bubbles budding from the rough er they can come from the rough er too. But these little bubbles that you see here these little vesicles thes little membrane bubbles they're important for carrying materials throughout and connecting interconnecting all of the organelles of the Indo membrane system. Now this year concludes our introduction to the end of plasma ridiculous and the two main types the rough E. R. And the smoothie er, and we'll be able to get some practice applying these concepts as we move forward in our course and continued to talk Maura about organelles of the end of membrane system as well. So I'll see you all in our next video.

Which of the following is most likely to have the greatest concentration of smooth endoplasmic reticulum?

• A. A cell that secretes enzymes.
• B. A cell that destroys pathogens.
• C. A cell that makes steroid hormones.
• D. A cell that engages in photosynthesis.
• E. A cell that manufactures proteins.

in this video, we're going to talk about the third organ L of the Endo Membrane System, which is the Golgi apparatus now, molecules that air synthesized or built in the Endo Plas Mick Ridiculous um, such as proteins in the rough er and lipids in the smooth E r. These molecules are transported by vesicles or tiny little membrane bubbles, and these molecules that air transported by vesicles they can be transported to the Golgi apparatus. And so the Golgi apparatus is really just a stack of flat membrane ISS sacks. And because it is membrane ISS, it's no surprise that it's part of the Endo membrane system. Now the stacks of flat membrane sacks have a scientific name that, uh, is Sastre knee. And so cistern e is just the scientific name that's referring to those flat membrane a sax. Now the Golgi apparatus. Its function is to act as a processing center because it's able to receive packages, modify the contents of the packages and then deliver the packages. And so it's acting like a processing center in that way. And so once again, the Golgi apparatus is capable of receiving vesicles that our transport remember the vesicles are transporting molecules that are being synthesized by the ER, either proteins or lipids. So the Golgi apparatus receives those vesicles, and then it modifies the vesicles contents, which would again either be proteins or lipids. And then, after it modifies the vesicles contents, it will actually repackage the modified contents back into vesicles for export from the Golgi apparatus. And so, once again, this is why the Golgi apparatus functions as a processing center because it receives vesicles. It modifies the vesicles contents, and then it repackages the contents for export either out of the cell or to a different location within the cell. And so this means that the Golgi apparatus is going to have a receiving end where it receives vesicles, and that's going to be the receiving end of the Golgi apparatus is referred to as the cysts end of the Golgi apparatus and then the shipping end, which is basically the end that repackages and exports. The shipping end of the Golgi apparatus is going to be the Trans and of the Golgi apparatus. Now, some of the vesicles that are being shipped from the Golgi apparatus can actually fuse with the cell membrane for secretion. And so this is why the Golgi apparatus here is gonna be one of the last organelles that air involved with protein secretion. And so let's take a look here at our image down below at the Golgi apparatus to get a better understanding here. And so the Golgi apparatus in this image is, uh, this pink structure that you see right here. This is the Golgi apparatus. And so you can see its position relative to other organelles that are around that we already talked about in our previous lesson. Videos such as the nucleus, the rough Endo Plasvic. Ridiculous. Um, and the smooth and a plasma ridiculous. So here we're talking about the Golgi apparatus. So here's a different view here of the Golgi apparatus and some of these other organelles notice It's a bird's eye view. Where here we have the nucleus here. We're showing you on Lee the smooth er for simplicity's sake. The I'm sorry, the rough er just for simplicity sake, we're only showing you the rough er the one that's here in blue. And the rough er recall is studded with ribosomes. And, uh, those rhizomes make proteins and those proteins can end up on the inside of vesicles, these little tiny membrane bubbles. And so this here is representing a vesicles that's carrying a protein because it's coming from the rough yard. And so these vesicles, they're capable of fusing with the Golgi apparatus, which were showing you right here. So the vesicles, the receiving end of the Golgi apparatus, recalled. The receiving end of the Golgi apparatus is going to be the cysts end of the Golgi apparatus. So here the receiving end is going to be the cysts end or the CIS face of the Golgi apparatus. And then once those contents make it to the Golgi apparatus, they get modified, and they make their way through the Golgi apparatus until they get to the other side of the Golgi apparatus, which is going to be the shipping end of the Golgi apparatus, or the trans end of the Golgi apparatus. And so down below, right here. This end over here is going to be the trans end of the Golgi apparatus or the trans face of the Golgi apparatus. And so this means that vesicles are going to be created at this end, and these vesicles are carrying the modified contents and these vesicles they can travel to the cell membrane, as we indicated up above, they can travel infused with the cell membrane for secretion. And so, at this point, traveling to the cell membrane, the contents can be exported and released to the outside of the cell on DSO. Once again, each of these flat sex that you see here these flat membrane a sex they're referred to as, uh, sister knee like this. So the cistern e once again are the flat membrane iss sacks of the Golgi apparatus. And so this here concludes our introduction to the Golgi apparatus and, uh, the organelles that air involved with protein secretion, and so we'll be able to get some practice applying the concepts that we've learned in our next video here, so I'll see you all there.

Which of the following is the most common pathway taken for a newly synthesized protein to be secreted?

• A. Rough ER → Golgi→ Transport vesicle → Nucleus.
• B. Golgi → Rough ER → Lysosome → Transport vesicle → Cell membrane.
• C. Rough ER → Golgi → Transport vesicle → Cell membrane.
• D. Rough ER → Lysosome → Transport vesicle → Cell membrane.