Erythrocytes - Video Tutorials & Practice Problems
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Structure of Erythrocytes
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In this video, we're going to talk about the structure of erythrocytes. And so erythrocytes, red blood cells or RB CS are relatively small cells in comparison to most other body cells. In fact, they're about three times smaller than most other body cells. So that's a pretty notable fact, also these erythrocytes or red blood cells are biconcave shaped, which really just means that there are these flattened discs as you can see here with a depressed center. And so notice that we're showing you a cross section of the red blood cells so that you can see that biconcave shape even better. And notice once again that they are a flattened disc with a depressed center. And so really the biconcave shape of these red blood cells is very similar to the shape of a donut because they are both flattened discs with a depressed center. However, most donuts have a complete hole going through the middle of them. Whereas that's not the case with these red blood cells, the red blood cells only have a depressed center, not a complete hole going through the middle. Now, these erythrocytes or red blood cells are also different than most other body cells and that they lack a nucleus. And so these erythrocytes or red blood cells are considered a nucleus since they do not have a nucleus and they also lack many organelles as well, including mitochondria, endoplasmic reticulum and golgi apparatus and more as well. And so the structure of these erythrocytes or red blood cells is going to be highly linked to its function. Which recall from our previous lesson videos that the main function of these erythrocytes or red blood cells is gas transport, oxygen, gas and carbon dioxide gas transport. Now, the biconcave shape of these erythrocytes helps to increase or increases the red blood cells overall flexibility so that it can fit into really tight and narrow spaces. And the biconcave shape also increases the red blood cells surface area to volume ratio, which is critical to help maximize the efficiency of gas exchange and gas transport. And so again, it's the structure that's going to help dictate the function. Now, these erythrocytes or red blood cells also have a meshwork of cytoplasmic proteins, including a family of proteins known as spectrin and spectrin is going to help maintain the red blood cells shape. And so what's important to note is that these erythrocytes or red blood cells are often going to need to fit into really tiny blood vessels or capillaries where the red blood cells themselves are actually bigger and wider than those blood vessels. And so what this means is that the red blood cells often need to fold up on themselves and bend in order to fit through the tight and narrow spaces of the capillaries. However, when those red blood cells get back into a larger vessel with more space, those red blood cells will spring back into their original biconcave shape. And again, it's these cytoplasmic proteins like spectrum that helps to maintain the red blood cells shape. Now, a very important fact to note about red blood cells is that they are packed with tons and tons of hemoglobin, which can be abbreviated as HB. And so this hemoglobin is really just a protein that functions in gas transport, specifically oxygen and carbon dioxide gas transport. And as we move forward in our course, we'll get to talk more about the structure and function of the hemoglobin molecule. But for now, what you should note is that each individual red blood cell is packed with tons of hemoglobin protein. And so let's take a look at our table down below so that we can differentiate between erythrocytes on the left and most other body cells on the right. And so the first thing that you'll notice is that erythrocytes are quite small in their size, they're smaller in size in comparison to most other body cells. Uh In fact, the diameter of the erythrocyte is about 7.5 micrometers. Uh whereas most other body cells again are going to be larger in size and have a diameter that is about 25 micrometers. And so again, most other body cells are about 3.5 times larger than erythrocytes. Now again, erythrocytes in terms of their shape, they are biconcave in their shape, which means that they have this flattened disc with a depressed center. Whereas most other body cells do not have a biconcave shape. Also, erythrocytes are going to lack a nucleus. So they are a nucleus and they also lack many organelles such as mitochondria, endoplasmic reticulum and golgi apparatus. For example, whereas most other body cells do contain a nucleus and they also contain organelles as well. Now again, the erythrocytes are coated with flexible proteins such as spectrum, which helps them to maintain their shape even after they squeeze through tiny, tiny blood vessels and have to fold up and uh bend. Whereas most other body cells are not going to be coated with those spectrum proteins. And then last but definitely not least erythrocytes are going to be packed with tons and tons of the hemoglobin protein molecules, which again are going to function in gas transport, oxygen and carbon dioxide gas transport. Whereas most other body cells are not going to be packed with those hemoglobin proteins. And so this here concludes our brief lesson on the structure of erythrocytes. And as we move forward in our course, we'll be able to learn more. So I'll see you all in our next video
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example
Erythrocytes Example 1
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So here we have a pretty straightforward example, problem asking which of the following statements about erythrocytes is false. And we've got these four potential answer options down below. Option A says they use mitochondria to make their own A T PB says they are smaller than the average body cell. C says their shape is flexible and D says they don't have a nucleus. Now, of course, recall from our last lesson video that erythrocytes or red blood cells lack a nucleus and many organelles including mitochondria and so erythrocytes don't have mitochondria. And to say that they use mitochondria to make their own A TP is simply a false statement again because they don't have mitochondria. And so they have to use other means to make their own A TP. And so what this means is that answer option A is the false statement that we are looking for. So we can indicate that A here is the correct answer to this problem. And these other statements that we see down below are all true statements. It's true that erythrocytes are smaller than the average body cell. In fact, they're about three times smaller than the average body cell, which is pretty significant. It's also true that their shape is flexible. They have a biconcave shape that increases their flexibility. They lack a nucleus in many organelles, which also adds to their flexibility since that helps them be able to bend and fold easier. Uh They also have proteins such as spectrum which increases their flexibility and helps them maintain their shape even after they have to fold and bend through tiny blood vessels and capillaries. And when they get back into a larger space, they can spring back into their original shape because of those proteins, uh also erythrocytes don't have a nucleus. And so they are considered a nucleus. So again, option A is the correct answer to this problem. Now, it is interesting to think what if erythrocytes did have mitochondria. Well, recall from previous videos that mitochondria use or consume oxygen to make a TP and erythrocytes play a huge role in delivering oxygen to tissues. And so if erythrocytes did have mitochondria, they would be consuming some of the oxygen that they were supposed to be delivering to the tissues. And so that would be similar to a pizza delivery guy taking a bite out of one of the slices before they deliver it to you. It's simply not going to work. And so thankfully, our erythrocytes have evolved to dispose of their mitochondria. And so again, this concludes this problem. Option A is the correct answer and I will see you all in our next video.
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Problem
Problem
What is the primary function of the protein spectrin in erythrocytes?
A
To allow efficient gas exchange of oxygen and carbon dioxide into and out of erythrocytes.
B
To maintain the shape of erythrocytes and allow them to change shape when needed.
C
To make ATP, as there are no mitochondria in erythrocytes.