Learning About Cell Biology

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The distinct compartmentalized components of the parts of cells are called organelles. Each organelle performs a specific function

These organelles are:

Nucleus

Endoplasmic reticulum

Golgi apparatus

Vesicles

Lysosomes

Mitochondria

Some parts of the cell will provide structure:

Plasma membrane

Cytoskeleton

We will go through each one of these organelles on the following pages, but here is a quick overview:

The Nucleus is probably the most important part of the cell because it contains each organism's unique DNA. The DNA will never leave the nucleus, instead it is copied into RNA and that copy is transported out of the nucleus through pores or openings in the nuclear membrane. The fluid outside the nucleus is called the cytoplasm. Once the RNA reaches the cytoplasm it can be translated into proteins. These proteins all have specific jobs to do in the body. Sometimes they need to be modified before leaving the cell, and other times they are destroyed by the cell.

The Endoplasmic Reticulum is a thin ribbon-like membrane close to the nucleus that acts as a transportation system for RNA. When RNA exits the nucleus through the nuclear pores it passes into the Rough Endoplasmic Reticulum (RER) where ribosomes help translate the RNA into proteins that correspond to the genetic code. After the RER translates the RNA into a protein, the protein passes to the Smooth Endoplasmic Reticulum (SER) where it begins to be processed. Once this initial processing is finsihed the proteins are shuttled through the cytoplasm by microtubules.

Microtubules are like a scaffolding system in the cytoplasm.

The Centriole is also called the microtubule organizing center and enables these microtubules to lengthen and shorten as necessary to shuttle proteins throughout the cytoplasm. It is part of the Cytoskeleton.

The Golgi apparatus is a processing center (like a UPS hub) for proteins where other molecules, such as sugars, can be added. Once the proteins are processed they bud off into vesicles and can then fuse with the plasma membrane and leave the cell.

The Lysosome can be compared to a garbage dump. The pH inside this organelle is low, acidic, and it degrades proteins that are no longer necessary or are a danger to the cell.

The Perixisome is like the lysosome and functions to break down cells that that can be dangerous.

The Mitochondria is where metabolism takes place. These organelles make all the energy (in the form of ATP) that the cell and the organism would require. The mitochondria are special because it contains its own DNA.

The Plasma Membrane is what separates the inside of the cell (intracellular) from the outside (extracellular). It is composed of lipid (fat) molecules that prevent hydrophilic (water loving) molecules from passing though. Hydrophobic (water hating) molecules however, can pass through the plasma membrane.