Cell Organelles

16/09/2010 § 1 Comment

In today’s class, I re-learned the basics of organelles and inner structures inside a cell. By ‘relearn’, I mean that I’ve learned of mitochondria, Golgi apparatuses, ERs, and other internal characteristics of eukaryotic and prokaryotic cells. Of course, I began studying it back in 6th grade so the level we’re studying cells right now is much higher.

In any case, firstly, prokaryotes are the smallest and most basic form of life there is. They like to “keep things simple”, don’t have nuclei and don’t have any organelles, either. But we didn’t really discuss prokaryotes as much this class as we did eukaryotes. Eukaryotes are the ‘cars’ we talked about last class. For some people, a prokaryote is a bicycle that helps them get to school (if they live on the island, like me) but the eukaryote is the Lexus that brings them to Sannomiya and back with style. In general, a eukaryote is obviously more advanced and can do much more than a prokaryotic cell can. This is because of the many smaller compartments that a eukaryotic cell has inside its structure.

Now, there are probably multiple reasons why a cell needs a various amount of smaller compartments but the main reason is that the smaller compartments are needed to do its own individual specialized function to help sustain the cell. In class, this cooperative relationship between all the organelles in a cell was described as the economy. Many jobs help supply the economic market (and all other types of markets) and keeps the economy alive and working. The same goes for all cells out there. The multiple organelles (cell membrane, nucleus, lysosomes, ER, etc.) all work together to keep the cell alive and working.

First, the  membrane has a rather important role in keeping the cell and its organelles safe from unfamiliar substances and bacteria, too. The membrane itself and the proteins attached to it lets in certain substances and keeps other out. Nearly all organelles have membranes around them and they are all the same. All membranes are made of phospholipid bilayers except for protein membranes, which will vary depending on the type of protein.

The nucleus, as we’ve repeatedly mentioned in class, holds all of the information living creatures inherit from their parents. This information tells our cells what kind of proteins to make and then from there, the proteins do the rest, distributing themselves throughout the cell or even out of the cell. The sequence of nucleotides in DNA directs the sequence of amino acids, which make proteins in ribosomes.

Next, the endoplasmic reticulum is like the inner highway of a cell because they are some proteins’ means of transportation and also help the rest of the proteins get around the cell. There are two parts of the endoplasmic reticulum (ER, for short). The rough ER is considered rough because it is the part of the ER that has many ribosomes attached to the surface and under an electron microscope, the exterior looks rough and bumpy. Obviously with all those ribosomes, the rough ER is where many proteins are made. In reality, the ribosomes on the surface are always working and producing proteins and is very similar to a 24/7 factory; always making things. In contrast, the smooth ER has no ribosomes attached to its exterior (and is therefore smooth) and instead processes molecules inside its tubes.

The function of the ER can be seen through its form (which relates to the essay question!) because of its many folds that form passageways (like hallways, almost) that the proteins can weave through. So for example, the proteins that have already been made by the rough ER are then sent inside the ER to move through the highway, later packing the proteins into vesicles.

Afterwards, the proteins are sent to Golgi apparatuses, where the proteins encounter what could be called the post office. The proteins in the vesicles are taken and chemically modified, then repacked. (Like in a post office. The package is taken, examined, repacked and relabeled.)  The proteins are put into new vacuoles are released from the Golgi apparatus to be distributed to other organelles (they are distributed by exploding, literally) or outside of the cell.

Also, lysosomes go around the cells to break down food. They are membrane-bound organelles. These organelles have very violent and rough characteristics and, though we haven’t really studied their structures a lot, they function by cutting things down to very small bits. (A very good example was the destruction of bacteria when one is sick). Lysosomes also break down old organelles that no longer function efficiently enough for the cell.

Finally, the mitochondrion is the organelle that’s like the powerhouse of the cell. It harvests energy from the nutrients and foods an organism eats and turns it into ATP, our energy currency.

All of the previous organelles are all in animal cells and are also in plant cells but plant cells have three different organelles that animal cells don’t have. They have chloroplasts, which are the organelles that use the energy harvested from sunlight to make carbohydrates with carbon-dioxide and oxygen. These organelles are vital providers of energy for the cell.

Plant cells also have cell walls that are rigid and surround the cell membrane. It is thick and made of proteins and carbohydrates, supporting the shape of the plant and protecting the cell from damage.

Finally, the central vacuole is a large shape (also membrane-bound) that stores water and other substances. These vacuoles, when a plant is being nourished and watered, puffer up and enlarge with the water it’s storing. The fullness of the vacuole helps the plant stand rigidly and when the plant is being malnourished, the vacuole is not full enough, therefore causes the plant to wilt.

So now I know many types of organelles and their functions and also have a general idea of how their structure helps their functions and jobs. Some examples of this would be the ER, central vacuoles in a plant and even membranes. One could even take the subject of phospholipid bilayers and use them to explain how their form relates to their function.

§ One Response to Cell Organelles

  • Dave Ferguson says:

    Kari,

    Another excellent post: Your writing shows thorough understanding and you are expressing ideas with clarity. Keep up the great work.

    Mr. F.

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