Introduction to Eukaryotic Organelles: Study with Video Lessons, Practice Problems & Examples

Eukaryotic cells contain various membrane-bound organelles, with differences between animal and plant cells. Key organelles include lysosomes, unique to animal cells, and chloroplasts and cell walls, found only in plant cells. Ribosomes, non-membranous organelles, are essential for protein synthesis through the process of translation. They can be free-floating in the cytoplasm or attached to the rough endoplasmic reticulum. Understanding these organelles is crucial for grasping cellular functions and processes, including the endomembrane system and energy-related organelles like mitochondria and chloroplasts.

Introduction to Eukaryotic Organelles

In this video, we're going to begin our introduction to Eukaryotic Organelles or organs inside of the cells. And so recall from our previous lesson videos that eukaryotic cells contain several membrane-bound organelles. And so moving forward in our course, we're going to talk about many of these membrane-bound organelles. Now it's important to note that both animal and plant cells are eukaryotic, and so that means that they both contain eukaryotic organelles. However, that being said, some of the organelles of animal and plant cells will actually differ from each other, and so that's important to keep in mind. And so down below in our example of eukaryotic organelles, notice that we're showing you our representation of an animal cell over here on the left-hand side and our representation of a plant cell over here on the right-hand side. And what you'll notice is that the organelles that are in the middle here are organelles that are shared between both animal and plant cells, whereas the organelles that are over here on the far left are only found or associated with animal cells, whereas the organelles that are on the far right are only found and associated with plant cells. Now it's also important to keep in mind that these are just general representations of animal cells and plant cells, but not all animal cells and plant cells are going to have all of these organelles. They're just generalized representations. And so, when we're talking about the animal cell, we're going to be focusing on how lysosomes are one of the characteristic organelles that are only found in animal cells but not found in plant cells. And when we're talking about plant cells, we're going to talk about how chloroplasts and cell walls are characteristic of only plant cells, but not so much in animal cells. Whereas, here in the middle, once again, we have organelles that are common to both animal and plant cells. And moving forward in our course, we're going to talk a lot more about each of these organelles that are here. So, for example, the mitochondria, which we're not just eukaryotic cells, but also prokaryotic cells too that we're not just eukaryotic cells, but also prokaryotic cells too that we're not talking about here. They both have a rough ER or a rough endoplasmic reticulum, as well as a smooth endoplasmic reticulum, that we're showing you here. They both also have structures that we call ribosomes, which are these tiny little blue dots that we're showing you. They both have a Golgi apparatus, and they both are going to have peroxisomes like what we see here. And so once again, we're going to be talking about each of these organelles and their own separate videos moving forward. So this is just, basically for you to use to figure out what it is that we're going to be talking about moving forward. So this here concludes our brief introduction to eukaryotic organelles, and once again, moving forward in our course, we're going to talk a lot more about each of these organelles. So I'll see you all in our next video.

Ribosomes

In this video, we're going to introduce ribosomes, and it's important to note that sometimes ribosomes are referred to as non-membranous organelles, which really just means that sometimes ribosomes are referred to as organelles that are not made of membranes, and that's what the non-membranes part refers to. Now, this is important to note because moving forward in our course, we're going to talk about a lot of different types of organelles, and most of those organelles are made of membranes. But once again, these ribosomes are not made of membranes. Now, your textbooks and professors will again sometimes refer to these ribosomes as organelles, but we need to remember that these ribosomes are non-membranous organelles. Now, ribosomes we have mentioned before in some of our previous lesson videos, but what exactly do these ribosomes do for the cell? And so these ribosomes are really just molecular machines that build proteins in all living cells and so ribosomes are found once again in all living cells regardless if those cells are plant cells or animal cells or eukaryotic cells or prokaryotic cells it does not matter. Again, ribosomes are found in all living cells, and they are really molecular machines that build proteins. Now the process that's conducted by these ribosomes that builds these proteins has a specific name that is called translation. And so translation we can define as the process that is conducted by ribosomes that allows them to build proteins. And later in our course, we're going to talk a lot more details about this process of translation, but for now in this video, all you should know is that ribosomes will build proteins by performing a process called translation. Now these ribosomes when they are inside a cell, they can either be free ribosomes that are free-floating in the cytoplasm or they can be attached ribosomes, and these attached ribosomes are not free-floating instead these attached ribosomes are going to be attached to another organelle, for example, the rough endoplasmic reticulum, that we'll get to talk more about this rough endoplasmic reticulum later in our course. But for now, if we take a look at our image down below, we can get a better understanding of these free and attached ribosomes and so notice right in the middle what we're showing you is our representation of our Eukaryotic cell and, notice that we have these blue circles throughout our Eukaryotic cell and they're all over the place, and so you can find all of these blue circles in your Eukaryotic cells. Now these blue circles, if we were to zoom into one of these blue circles, that's what this image over here is showing, you would notice that these blue circles are indeed ribosomes. And again these ribosomes are going to be performing translation and building proteins. Now, all of these blue circles that you see that are free-floating in the cytoplasm are going to be free ribosomes. And recall that the cytoplasm is really just going to be the area that is inside of a cell but outside of the organelle. So all of these, blue circles that you see, in these little areas here, those would be free ribosomes. And so these are going to be floating in the cytoplasm of the cell. So we can fill that in here. And again, these ribosomes are going to be performing translation, and so the ribosome in this image is represented by this blue structure that you see over here. And notice that this ribosome is building a chain of protein, here so we can say that this is our growing protein that is being built by the ribosome. Now again, some of the ribosomes will be free ribosomes, free-floating in the cytoplasm, but other ribosomes that you can see in these positions are attached ribosomes that are attached to another organelle. And so if we zoom into this area right here what you'll notice is that we can see some attached organelles, some attached ribosomes to, the rough endoplasmic reticulum. And so notice that the rough endoplasmic reticulum in this image is, being indicated by this, reddish structure that you see right here. And what you'll notice is that this rough endoplasmic reticulum, has these attached ribosomes. So, these attached ribosomes are attached to the rough endoplasmic reticulum. And again, we'll get to talk more about the rough ER or the rough endoplasmic reticulum more as we move forward in our course. But for now, notice that within these, eukaryotic cells you'll find some ribosomes that are free ribosomes, free-floating in the cytoplasm, and you'll find some ribosomes that are attached ribosomes that are attached to other organelles such as the rough ER for example. And so this here concludes our brief introduction to ribosomes, and we'll be able to learn more as we move forward in our course, so I'll see you all in our next video.

What biomolecule does a ribosome synthesize in all types of cells?

• A. Lipids.
• B. Carbohydrates.
• C. Nucleic Acids.
• D. Proteins.
• E. Amino Acids.

Map of the Lesson on Eukaryotic Organelles

In this video, we're going to introduce our map of the lesson on eukaryotic organelles which is down below right here. And so because this is a map of our lesson you can use it like a map or a table of contents to figure out what direction to take multiple times as we move forward through our course. And so let me explain to you how this map works. Of course, it's going to start up at the top here with these eukaryotic cell organelles, and everything down below are going to be eukaryotic cell organelles. And so we're going to be exploring the leftmost branches first, and then once we're done exploring the leftmost branches, we'll start to explore the right branches and so we'll start off talking about the endomembrane system and protein secretion, which is going to include the nucleus, the endoplasmic reticulum, the rough ER and the smooth ER, the Golgi apparatus, and the cell membrane. And once we finish talking about the protein secretion, we'll move on to cellular digestion focusing on lysosomes, peroxisomes, and vacuoles. Once we've finished covering these leftmost branches, then we'll start to focus on the right branches. So we'll go into energy-related organelles including the mitochondria and the chloroplasts. Once we've covered these, then we'll move on to talk about the cytoskeleton, which includes microfilaments, intermediate filaments, and microtubules, which are going to somewhat resemble our own skeleton. So that's why we have the little image of a skeleton here. And then of course, once we've covered that, we'll finally cover the cell junctions including tight junctions, anchoring junctions, gap junctions, and plasmodesmata. And so, again, this here is our map of the lesson on eukaryotic organelles, and we'll see you in our next video to learn more about the endomembrane system. So I'll see you all there.

Using the map above, which of the following is NOT a component of the cytoskeleton in eukaryotic cells?

• A. Intermediate filaments.
• B. Microtubules.
• C. Tight junctions.
• D. Microfilaments.

Using the map above, what two organelles produce cellular energy in eukaryotic cells?

• A. Mitochondria and Golgi Apparatus.
• B. Chloroplast and Nucleus.
• C. Lysosomes and Rough ER.
• D. Chloroplast and Smooth ER.
• E. Mitochondria and Chloroplasts.
• F. Microtubules and Chloroplasts.

Here’s what students ask on this topic:

What are the main differences between animal and plant cell organelles?

Animal and plant cells, both eukaryotic, share many organelles but also have distinct differences. Animal cells contain lysosomes, which are involved in digestion and waste removal, and are generally absent in plant cells. Plant cells, on the other hand, have chloroplasts for photosynthesis and a rigid cell wall for structural support, both of which are absent in animal cells. Additionally, plant cells often contain large central vacuoles for storage and maintaining cell turgor, whereas animal cells may have smaller, more numerous vacuoles. Understanding these differences is crucial for studying cellular functions and processes unique to each cell type.

What is the function of ribosomes in eukaryotic cells?

Ribosomes are essential molecular machines in eukaryotic cells responsible for protein synthesis. They perform a process called translation, where they read mRNA sequences to build polypeptide chains, which then fold into functional proteins. Ribosomes can be found free-floating in the cytoplasm or attached to the rough endoplasmic reticulum (ER). Free ribosomes typically synthesize proteins that function within the cytoplasm, while those attached to the rough ER produce proteins destined for secretion or for use in the cell membrane. Ribosomes are unique in that they are non-membranous organelles, found in all living cells, including prokaryotes.

What is the endomembrane system and its components?

The endomembrane system is a group of interconnected organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins. Key components include the nucleus, which houses DNA and is the site of transcription; the endoplasmic reticulum (ER), with rough ER involved in protein synthesis and smooth ER in lipid synthesis; the Golgi apparatus, which modifies and packages proteins and lipids for transport; and the cell membrane, which regulates the entry and exit of substances. This system is crucial for maintaining cellular organization and function.

How do mitochondria and chloroplasts differ in their roles within eukaryotic cells?

Mitochondria and chloroplasts are both energy-related organelles but serve different functions. Mitochondria, found in both animal and plant cells, are the powerhouses of the cell, generating ATP through cellular respiration. They convert chemical energy from nutrients into a form usable by the cell. Chloroplasts, found only in plant cells and some algae, are responsible for photosynthesis. They capture light energy to convert carbon dioxide and water into glucose and oxygen. This process not only provides energy for the plant but also contributes to the oxygen supply for other organisms. Both organelles have their own DNA and double membranes, indicating their evolutionary origins from ancient symbiotic bacteria.

What is the role of the cytoskeleton in eukaryotic cells?

The cytoskeleton is a network of protein filaments and tubules that provides structural support, shape, and organization to eukaryotic cells. It consists of three main components: microfilaments, intermediate filaments, and microtubules. Microfilaments, made of actin, are involved in cell movement and muscle contraction. Intermediate filaments provide mechanical strength and help maintain cell integrity. Microtubules, composed of tubulin, are crucial for cell division, intracellular transport, and the maintenance of cell shape. The cytoskeleton also plays a role in anchoring organelles and facilitating communication between them, making it essential for various cellular processes.