The organelles of a cell are much like the organs of your body. In fact, the word organelle means little organ. Learn about important organelles of a human cell, such as the nucleus, endoplasmic reticulum, mitochondria, lysosomes and Golgi bodies.
I’d like you to meet Joe.
Joe is a human cell who has been feeling a bit sluggish lately. He has decided to visit the local cell doctor for a checkup. In the examining room, the doctor can see that Joe looks tired and rundown, so he starts a full examination. First, the doctor inspects Joe’s outer covering, known as his cell membrane, or plasma membrane, as it is also called. After a few moments of observation the doctor notes that the cell membrane is working properly as it controls the movement of substances into and out of the cell body.
Satisfied that Joe’s protective covering is fine, the doctor asks Joe to open up so he can take a look at his organelles. Organelles are the metabolic machines of the cell. It’s inside the organelles where most of the activities of the cell take place. This makes them much like the organs of your body; in fact, ‘organelles’ means ‘little organs.’ The doctor is convinced that if anything is wrong with Joe, the problem will be found by closely inspecting his organelles, so he gets to work on his internal examination.
A quick scan shows that all of the organelles are suspended in the gel-like cytoplasm as they should be. Because of the doctor’s vast experience in dealing with cases like Joe’s, he knows that he should start his internal exam with the nucleus.
After all, the nucleus is the control center of the cell – what you might think of as the brain of the cell. The nucleus has its own membrane. This membrane has pores that allow the transport of certain materials into and out of the nucleus. For this part of the exam, doc needs to put on his special high-power viewing googles so he can look inside one of the pores and check out the chromosomes found inside the nucleus.
After a few tweaks to get the goggles focused, the doctor starts to see the threadlike chromosomes come into view. Chromosomes are very important because they contain the genes and genetic material of the cell. Doc knows that someday Joe will want to divide and make his own family of new cells. When that happens, Joe will pass along a copy of this genetic material to his offspring. Joe breathes a bit easier when the doctor tells him that all is well with his nucleus and chromosomes.
Doc moves on to another of Joe’s organelles known as the endoplasmic reticulum, or ER for short. This is a collection of tube-like structures within the cytoplasm.
The endoplasmic reticulum acts as a highway transporting substances throughout the cell. Just like a highway you drive on, the endoplasmic reticulum connects different areas. This allows materials to be moved from one part of the cell to the next. The doctor grows a bit concerned when he notices that the surface of some of the ER is nice and smooth, but other surfaces are rough.
Much to his relief he soon remembers that there are two types of endoplasmic reticulum: smooth ER and rough ER. The rough ER’s surface looks bumpy because it’s covered with tiny organelles called ribosomes. Ribosomes can also be found floating around freely in the cytoplasm. They are very small, but they have a big job, which is to make proteins.
So far, doc can’t find anything wrong with Joe. Then he recalls that Joe’s complaint was that he was feeling sluggish.
This makes him think that Joe might be experiencing a power problem. Doc knows exactly which organelle to check, the mitochondria. This is a logical choice because the mitochondria are the powerhouses of the cell.
It’s inside the mitochondria where molecules of ATP are made. ATP is the fuel source for cellular activity.There are many mitochondria floating in Joe’s cytoplasm. Doc can’t inspect each one, so he focuses his attention on just one of the oblong organelles. The outer one looks smooth, and the inner membrane is highly folded, which is what he wants to see. These folds provide more surface area or space for the process of cellular respiration to take place.
Cellular respiration is the process that converts food into usable energy. Doc hooks up his power meter to the mitochondrion and finds that the output of energy is in the normal range.
Doc thought for sure the mitochondrion would be the problem.
He scratches his head and thinks hard. He knows that before food nutrients go to the mitochondria they have to be digested. He knows that this is the work of lysosomes. Lysosomes contain enzymes that help digest food and cell debris.
Doc wonders if this organelle might be malfunctioning. He decides to take a look, but knows he has to be very careful. Lysosomes are called suicide sacs. If the enzymes inside the lysosome get out, they could digest and destroy Joe.
Everything checks out with the lysosomes. Doc can think of just one more organelle he wants to look at, the Golgi bodies, also called the Golgi apparatus.
These organelles are the packaging and distribution centers of the cell. Upon inspection, doc watches as Joe’s Golgi bodies take in proteins and other substances and package them into little units that are then released out of the cell. This is exactly what is supposed to happen. Doc determines that Joe is perfectly healthy. He tells Joe that all he needs is some rest, and he should be feeling better in no time.
Joe is relieved that all of his organelles are working properly. This knowledge alone gives Joe a renewed spring in his step as he leaves for home.
Let’s review. In this lesson we learned about the organelles, which are the metabolic machines of the cell.
The nucleus is arguably the most important organelle because it is the control center of the cell. Inside the nucleus we find chromosomes, which are threadlike structures that contain the genes and genetic material of the cell.Another organelle we learned about was the endoplasmic reticulum, or ER.
This is a collection of tube-like structures within the cytoplasm that acts as a highway transporting substances throughout the cell. ER can be either smooth or rough. Rough ER has ribosomes on its surface that make it bumpy. Ribosomes are small organelles that make proteins.
Mitochondria are the powerhouses of the cell. It is inside mitochondria that we see cellular respiration taking place. Cellular respiration is the process that converts food into usable energy so your cells have fuel to run on.
Before food nutrients can be converted to energy, they need to be digested. This is the job of lysosomes. Lysosomes contain enzymes that help digest food and cell debris.The last organelles we learned about were the Golgi bodies, which are the packaging and distribution centers of the cell.
They package up proteins, getting them ready to be released out of the cell.
Once you have reviewed this lesson you should be able to identify and recall the functions of the different organelles inside of a cell.