Cell Membrane | Enzymes | Prokaryotic and Eukaryotic Cells | RNA's Role | The Role of the Endoplasmic Reticulum and the Golgi Apparatus | Energy Capture and Storage | Mitochondria | Macromolecules | What Determines the Eukaryotic Cell's Shape? | Summary
|The Role of the Endoplasmic Reticulum and the Golgi Apparatus|
|CA GR.9-12 Biology 1.e.|
Inside the cell membrane there is the cytoplasm (also called “cell fluid” or cytosol). This cytoplasm is actually not just “fluid" -- it is a complex system of fibers, tubes, membranes, particles and organelles (little organs), all of which have very specific functions.
At the center of it all is the nucleus, which contains DNA, the genetic material we learned about in our last Instruction.
These are relatively tiny organelles. There are two different kinds of ribosomes: free ribosomes (which float “free” in the cytoplasm) and bound ribosomes (which are attached, to something called the endoplasmic reticulum).
Ribosomes are so important because they assemble (“sequence”) amino acids into proteins (as we also learned in our last Instruction). If a protein is going to be used inside the cytoplasm of a cell, it is generally built by free ribosomes and not by ones bound to the endoplasmic reticulum.
The Endoplasmic Reticulum
This brings us to an organelle called the Endoplasmic Reticulum. Scientists call it “ER” (like the TV show).
There are two different kinds of ER:
Smooth ER is not involved in protein synthesis. It is the site of the synthesis of fatty acids and
phospholipids. It is called “smooth” because it has no ribosomes on its surface.
It is shaped like little tubes, as you can see in this illustration:
As people consume more alcohol, they realize that they have to continue to drink more to get the same effect. This happens because more inactivating enzymes are being produced.
These inactivating enzymes are responsible for helping to detoxify the liver. A body’s production of more Smooth ER is just an example of how it tries to protect you from the toxic effects of alcohol.
These ribosomes are said to be “bound” to the ER. The largest number of bound ribosomes is found in cells that produce secretory products.
These secretory proteins (enzymes) are manufactured here. The term secretory just means that these proteins are made for secretion, or delivery outside the cell, into the body.
Once a protein has been synthesized (made), Rough ER creates a bubble around
it by pinching off a portion of its own membrane. This bubble is called a
The Golgi Apparatus
What’s the Golgi Apparatus?
First, you need to learn to pronounce it. The first three letters, G-O-L are pronounced “goal” and
the last two
The Golgi Apparatus was named for Camillo Golgi, the Italian physician who discovered it. It is sometimes also called the Golgi Body, the Golgi Region or the Golgi Complex (probably just to confuse us).
The Golgi Apparatus looks like a loose stack of pancakes. Plant cells contain many of these stacks, while animal cells have just a few.
The Golgi takes simple molecules it gets from the Rough ER and makes them bigger. Remember the transition vesicles? Well, these little transported packages, or vesicles have their contents modified inside the Golgi apparatus. Not only do these little packages get modified, they get “addressed” for delivery to their next destination. The packages that now carry the modified contents are called secretory vesicles. You might want to look back it will make this a lot easier to understand.
Here's how it works:
In many cases, the Rough ER, the Smooth ER and the Golgi Apparatus are actually attached to one other. This helps them work easily together -- even if what they do does sound pretty complicated to us.
Experiments for Home and Classroom
In this activity, students are invited to build a model of a cell and
then see how it divides. Each student starts out with a bowl of Jell-O™ --
and various edible objects are added to represent various organelles. The
endoplastic reticulum (ER) and the Golgi Apparatus are represented by Fruit
Roll-Ups™. At the end of activity, the "cell" can be eaten. Scroll down to
"Make a Cell." Click: