Introduction to Eukaryotic Organelles - Online Tutor, Practice Problems & Exam Prep

Eukaryotic cells contain various membrane-bound organelles, including lysosomes unique to animal cells and chloroplasts and cell walls exclusive to plant cells. Ribosomes, non-membranous organelles found in all living cells, are essential for protein synthesis through the process of translation. They can be free in the cytoplasm or attached to the rough endoplasmic reticulum (ER). 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 representing like this, are found in both animal and plant cells. The cell membrane is found in both animal and plant cells.

Remember, all cells have a cell membrane, not just eukaryotic cells, but also prokaryotic cells too that we're not talking about here. They both have a rough ER or 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 in 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. Ribosomes are sometimes referred to as nonmembranous organelles, meaning they are not made up of membranes. This is important to keep in mind because most of the organelles we will discuss moving forward are made up of membranes, but ribosomes are not. It's crucial to remember that ribosomes are nonmembranous organelles, as both textbooks and professors often refer to them simply as organelles.

Now, we have mentioned this term "ribosomes" a few times in our previous lesson videos, but what exactly are these ribosomes, and what do they do for a cell? Well, you can think of ribosomes as tiny molecular machines inside of cells that build proteins. Ribosomes are found in all living cells, regardless of whether those cells are prokaryotic or eukaryotic, or whether they are animal or plant cells. The process conducted by ribosomes that builds proteins is specifically named "translation."

Translation is the scientific term for the process conducted by ribosomes to build proteins. Later in our course, we will discuss this process in much more detail. For now, you should know that ribosomes build proteins by conducting this process called translation. It's also important to note that ribosomes can either be free ribosomes, which are free-floating in the cytoplasm, or attached ribosomes, which are not free and instead are attached to another organelle inside the cell, such as the rough endoplasmic reticulum (ER). We will talk more about the endoplasmic reticulum later in our course. But for now, let's take a look at this image we have here to better understand ribosomes.

Notice in the representation of a eukaryotic animal cell, these little tiny blue circles scattered throughout are ribosomes. If we zoom into one of these ribosomes, you will notice that some of them are free ribosomes, meaning they are just free-floating in the cytoplasm of the cell. The cytoplasm is the space inside the cell, in between organelles, and inside the cell membrane. However, whether they are free or attached ribosomes, their main function is to build proteins. This little blue ribosome we are zooming into is building a chain of amino acids which represents the protein being built.

Some of the ribosomes are attached ribosomes and are attached to another organelle such as the rough ER. If we zoom into this image, you'll see that the rough ER is this blue structure surrounding the nucleus. Attached to the rough ER are these tiny little blue dots, which are ribosomes specifically attached ribosomes. Free ribosomes make proteins that end up floating in the cytoplasm, but when the attached ribosomes make proteins, those proteins end up on the inside of the rough ER.

This concludes our introduction to ribosomes as machines that build proteins. We will apply some of these concepts moving forward in our course. 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, I'm going to introduce our map of the lesson on Eukaryotic Organelles, which is down below right here. And so this is actually a map of our lesson moving forward in our course. And so that means that you can use this image like a map, and you can actually use it to make predictions about what direction we're going to head into moving forward with our videos. And so let me explain to you how this map works. It works, starting at the top here.

So we have eukaryotic cell organelles at the very, very top. And then moving forward through our lesson, we're going to be exploring the leftmost branches first. And then once we've explored the leftmost branches, we'll start to explore the right branches. So for example, we're going to start here at eukaryotic cell organelles, then we're going to explore the leftmost branches first. So we'll talk about the endomembrane system.

Then we'll talk about the components that are part of protein secretion, which include the nucleus, the endoplasmic reticulum, the rough ER and smooth ER, the Golgi apparatus, and the cell membrane. And then once we've explored the leftmost branches, what we're going to do is we're going to zoom out and start to explore the right branches, which includes cellular digestion, lysosomes, peroxisomes, and vacuoles. And then once we've explored all of these branches over here on the left, we're going to zoom back out and start to explore the new branch over here, energy-related organelles, and then talk about the mitochondria and the chloroplasts. And then once we've covered these, we're going to move on to the next branch and talk about the cytoskeleton, which includes microfilaments, intermediate filaments, and microtubules, and has a lot of resemblance to actual skeletons, which is why we've got this little skeleton here. And then once we've covered the cytoskeleton components, last but not least, we'll move on to the cell junctions at the end, tight junctions, anchoring junctions, gap junctions, and plasmodesmata.

And so this is basically the way that we're going to cover videos moving forward in our course in that fashion, exploring the leftmost branches first. And so what this means is that you should be referring back to this map, as we move forward in our course, so that you can know exactly what direction we're headed in and how much is left within our lesson. And so keeping that in mind, of course, we're going to start off by exploring the leftmost branches first. So we're going to talk about the endomembrane system in our next lesson video. And 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, which are not found in animal cells. Both cell types share organelles like the nucleus, mitochondria, endoplasmic reticulum (ER), Golgi apparatus, and peroxisomes. Understanding these differences is crucial for studying cellular functions and processes specific to each cell type.

What is the function of ribosomes in eukaryotic cells?

Ribosomes are essential for protein synthesis in eukaryotic cells. They are non-membranous organelles found in all living cells, including both prokaryotic and eukaryotic cells. Ribosomes can be free-floating in the cytoplasm or attached to the rough endoplasmic reticulum (ER). Their primary function is to build proteins through a process called translation, where they assemble amino acids into polypeptide chains based on the sequence of messenger RNA (mRNA). This process is vital for cell growth, repair, and overall function.

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 nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, and vesicles. The rough ER is involved in protein synthesis and modification, while the smooth ER synthesizes lipids. The Golgi apparatus further modifies, sorts, and packages proteins and lipids for transport. Lysosomes contain digestive enzymes to break down macromolecules. 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 glucose and oxygen into energy, carbon dioxide, and water. Chloroplasts, found only in plant cells, are responsible for photosynthesis. They capture light energy to convert carbon dioxide and water into glucose and oxygen. While mitochondria provide energy for cellular activities, chloroplasts enable plants to produce their own food and release oxygen as a byproduct.

What is the role of the Golgi apparatus in eukaryotic cells?

The Golgi apparatus, also known as the Golgi complex, is a critical organelle in eukaryotic cells responsible for modifying, sorting, and packaging proteins and lipids for transport. It receives proteins and lipids from the endoplasmic reticulum (ER), processes them by adding carbohydrates or phosphates, and then sorts them into vesicles. These vesicles transport the modified molecules to their final destinations, either within the cell or to the cell membrane for secretion. The Golgi apparatus plays a vital role in maintaining cellular organization and function.