A cell is the smallest building block of life, meaning all living things are made of cells! Cells have membranes that surround them, separating the inside of the cell from the exterior environment. Inside the cell, there are different parts called organelles. Each organelle has its own role to ensure that the cell can stay healthy and work properly! Cells are necessary for life, since this is what performs the different functions needed. Depending on the cell, they will each have specialized tasks that they need to carry out. Organisms who are made of multiple cells are known as multicellular organisms whereas organisms made out of just a single cell are called unicellular, just like our friends Cera and Pora!
Cells can be divided into two main categories. If the cell contains a nucleus, they are considered eukaryotic. Prokaryotic cells, on the other hand, do not have a nucleus.
Here are five major differences:
Now that we have a basic understanding of the two main types of cells, we can explore deeper into the internal structure called organelles. You can think of organelles as tiny organs the cells have to help the cell survive and carry out life functions. Each organelle has a unique job to carry out, to contribute to the homeostasis of the cell!
Some important vocabulary that you should know, in relation to organelles are…
Cytoplasm: It is any of the content inside the cell, bounded by the plasma membrane. This includes all of the organelles.
Cytosol: The jelly-like substance inside the cell membrane. (The cytoplasm, excluding the organelles.)
Plasma membrane: It is a selectively permeable boundary between the cell’s internal and external environment. It regulates transport into and out of the cell. It is also used to communicate between and to other cells
Here are the different types of organelles:
Nucleus: This is where the genetic information is stored.
Ribosomes: They are made of ribosomal RNA and protein. This is where protein synthesis takes place. Ribosomes can be in two places.
Free ribosomes are suspended in the cytosol, making proteins for the cell.
Bound ribosomes can be attached to the outside of the endoplasmic reticulum, making proteins that will either be inserted into the membrane or proteins that will be exported.
Endoplasmic Reticulum: There are both rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). The difference between the two is that the rough one has ribosomes attached to the surface, giving it a rough appearance. The smooth one does not, which is why it is called smooth ER.
The smooth ER works to synthesize lipids. In simpler terms, it acts as a factory for the cell. It continuously makes lipids, including hormones and oils.
The rough ER has ribosomes that synthesize proteins. As proteins are being made, they enter the lumen, which is the interior space of the ER, where they get modified.
Golgi apparatus: This is basically the postal office of the cell. This is where proteins go once they are synthesized by the RER. Inside the golgi, these molecules go under more modification, sorting, and then are packed and transported in vesicles.
Vesicles: Vesicles are essentially just a small sac with liquid in it. It is used to carry stuff into and out of the cells. It transports materials.
Lysosome: This is like the cell’s recycling center. Here, digestion takes place and this is possible because of the digestive enzymes that lysosomes contain. These enzymes work best in acidic environments, such as lysosomes. Lysosomes are also able to break down old/damaged organelles and reuse its components. When lysosomes release certain enzymes, this can lead to apoptosis, which is the programmed death of the cell.
Mitochondria: The cell needs energy, such as ATP, to function. The mitochondria is where the production of ATP takes place.
Chloroplast: The chloroplast is only found in plant cells. Photosynthesis takes place in the chloroplast, converting light energy into chemical energy that the cell can use.
Vacuole: The vacuole is like the storage unit in the cell. There are various substances being stored such as water, waste products, and proteins.
Now, we can go more in depth about the differences between plant cells and animal cells.
Plant cells have chloroplasts, cell walls, and central vacuoles. The reason for this is because plant cells need to perform photosynthesis and it is also a way to store water and nutrients for themselves.
Animal cells, on the other hand, do NOT have chloroplasts or cell walls. Vacuoles can be present sometimes and if they are, they would be smaller. Instead, they possess flagella and cilia for movement.
We can see that these differences help both types of cell function differently. These traits help optimize energy production for plant cells whereas animal cells are able to have more mobility and communication, both of which are functions necessary for animal life.
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