For students who need to learn more about endoplasmic reticulum, you should understand that it’s all about the continuous membrane present in both animal and plant cells, but it’s absent in prokaryotic cells. Basically, it’s a membrane of flattened sacs and network tubules, and it serves many important functions within cells. The space that you can see in it is called the lumen.
Keep in mind that it’s a significant organelle present in the cells of all eukaryotic organisms and the interconnected network of tubes and fattened sacs in membranes. The latter ones are continuous and they join the outer nuclear membranes. Endoplasmic reticulum is present almost in all kinds of eukaryotic cells, except sperm and red blood cells. It has two basic types, including smooth and rough. The second one is often studied with ribosomes, which are the site of protein synthesis. It’s quite prominent in specific cell types, such as hepatocytes where the synthesis of active protein takes place. When it comes to its smooth type, it doesn’t have any ribosomes, but it plays an important role in metabolism processes.
Remember that endoplasmic reticulum serves many purposes within cells, such as transporting different proteins, folding them, and so on. When it comes to specific proteins, including glycoproteins, they move across its membranes. Besides, it’s responsible for marking them with a certain signal sequence. There are some other proteins that are headed outside this organelle and packed into special transport vesicles to be moved from cells through the cytoskeleton. This term is all about an efficient and important system of eukaryotic cells, and don’t forget that it contains proteins until they must be moved.
As you already know, it can be defined as some eukaryotic organelle that forms a certain network of vesicles, tubules, and cisternae within cells. Take into consideration that endoplasmic reticulum contains two basic regions that have different functions and structure. One of them is rough and contains the ribosomes attached to cytoplasmic membrane sides and is a series of some flattened sacs. The other one is smooth and it lacks such attached ribosomes and is a tubule network.
What are the most important functions of this eukaryotic organelle? To answer this question in full, you need to consider the following:
What is its structure? You should realize that endoplasmic reticulum is some extensive membrane network of sac-like structures of cisternae that are held together by a cytoskeleton. Phospholipid membranes enclose this space or the lumen that is continuous with the perinuclear one.
The surface of its rough type is studded with those ribosomes that manufacture proteins, and this is what provides it a rough appearance and name. Its smooth type consists of those tubules that are located near the periphery of cells and this network boosts a surface area to store important enzymes and their products. Keep in mind that rough endoplasmic reticulum is responsible for synthesizing proteins, while its smooth type synthesizes steroids and lipids. Other crucial functions that it has include metabolizing carbs and regulating such processes as drug detox, calcium concentration, and attaching receptors on cell membranes. This kind of organelle varies considerably so that it extends from cell membranes via a cytoplasm to form some continuous connection with nuclear envelopes.
In plant cells, endoplasmic reticulum functions as an efficient port that regulated the entry of proteins into membranes. It’s also important for storing and biosynthesizing lipids. There are many soluble membranes associated with molecular chaperones and enzymes, and the key functions of this organelle in plant cells include maturation and synthesis. However, it has other functions that are not available in animal cells. One of the main functions of endoplasmic reticulum is the right cell to cell communication, and it also serves as a great storing site for proteins. It contains structural proteins and enzymes involved in the process of lipid storage and oil body biogenesis. Another important detail is that it’s connected between cells through the plasmodesmata.
In animal cells, it’s all about a certain network of sacs that play a huge role in processing, producing, and transporting different chemical compounds to be used both outside and inside cells. Endoplasmic reticulum is also connected to double-layered nuclear envelopes that provide effective pipelines between the cytoplasm and nucleus in such cells. As you can see, it’s a multifunctional organelle that synthesizes membrane proteins and lipids while regulating intracellular calcium levels.
Wrapping Your Knowledge Up
As a biology student, you need to know that the main function of nucleus is to be a cell brain, while endoplasmic reticulum serves as an efficient packaging and manufacturing system. It works quite closely with ribosomes, tRNA, and mRNA. Structurally, it’s a network of those membranes that are found in cells and are connected to the nucleus. Don’t forget that these membranes are a bit different, and only specific cell functions can determine the structure and size of endoplasmic reticulum. As an example, some cells, including red blood cells and prokaryotes, don’t have this kind of organelle. Those cells that synthesize and produce many proteins require a lot of it, and you should take a look at liver or pancreas cells because they serve as its good examples.
There are 2 main types involved in this subject, and they both come with the same membrane types, but the key difference is that their shapes are different. When dealing with rough endoplasmic reticulum, it looks like some disks or sheets of bumpy membranes, while its smooth type resembles tubes. Take into account that the first type is called rough because ribosomes are attached to its surface.
Another thing that should be remembered is that the double membranes found in both types form sacs or cisternae. Protein molecules are collected and produced in the lumen, and when enough of them are synthesized, they are collected to be pinched off in vesicles that move further for extra distribution and packaging.
Smooth endoplasmic reticulum functions as a special organelle for storing. It plays a significant role when it comes to the storage and creation of steroids and lipids. If you’re more interested in steroids, you should know that they are ringed organic molecules that serve a number of purposes in organisms. It’s worth mentioning that they involve more than just building muscles. Those cells in the body that are responsible for releasing oil tend to have more smooth endoplasmic reticulum than others.
Pay attention to a rare type called sarcoplasmic that can store many ions in a certain solution that cells may need later on. When they need to perform some functions urgently, there is no sense in searching for a suitable environment for additional ions floating around. That’s because it’s much easier to store them in packs for easy usage. As an example, when you’re running and your muscle cells remain active, they require more calcium ions. The good news is that endoplasmic reticulum releases them when needed. When you’re relaxing, they will be stored for further use.
Its rough type may be studied with ribosomes because it plays an important role in the right packaging and synthesizing of proteins. Ribosomes must be attached to its membrane to make it rough. This organelle is also attached to the nuclear envelopes that surround the nucleus. Focus on a direct connection between the lumen of endoplasmic reticulum and a perinuclear space, as this is what allows the movement of molecules via both membranes.
For biology students, you should already know that the process of synthesizing proteins starts when mRNA moves to ribosomes from the nucleus, and it happens on the surface of this organelle. Ribosomes are important for building amino acid chains, and when proteins are complete, they are collected to be pinched off vesicles. Some of them are used in cells, while others are sent into the intercellular space.
In conclusion, you should find out more about the main functions of its smooth type, including making lipids or fats, producing steroids, such as vitamins and hormones, metabolizing carbs, such as starches and sugars, detoxifying or breaking down harmful elements to turn them into safe substances, and others. That’s why the importance of this eukaryotic organelle shouldn’t be underestimated by any student, especially when studying this subject.