Cellular organelles and structure
What is a cell
What’s found inside a cell
|Nucleus||DNA Storage||Room where the blueprints are kept|
|Smooth Endoplasmic Reticulum (SER)||Lipid production; Detoxification||Accessory production - makes decorations for the toy, etc.|
|Rough Endoplasmic Reticulum (RER)||Protein production; in particular for export out of the cell||Primary production line - makes the toys|
|Golgi apparatus||Protein modification and export||Shipping department|
|Peroxisome||Lipid Destruction; contains oxidative enzymes||Security and waste removal|
|Lysosome||Protein destruction||Recycling and security|
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
Golgi apparatus (aka Golgi body aka Golgi)
- Cytosol: the proteins that enter the Golgi by mistake are sent back into the cytosol (imagine the barcode scanning wrong and the item being returned).
- Cell membrane: proteins destined for the cell membrane are processed continuously. Once the vesicle is made, it moves to the cell membrane and fuses with it. Molecules in this pathway are often protein channels which allow molecules into or out of the cell, or cell identifiers which project into the extracellular space and act like a name tag for the cell.
- Secretion: some proteins are meant to be secreted from the cell to act on other parts of the body. Before these vesicles can fuse with the cell membrane, they must accumulate in number, and require a special chemical signal to be released. This way shipments only go out if they’re worth the cost of sending them (you generally wouldn’t ship just one toy and expect to profit).
- Lysosome: The final destination for proteins coming through the Golgi is the lysosome. Vesicles sent to this acidic organelle contain enzymes that will hydrolyze the lysosome’s content.
Plants and Platelets
Eukaryotes vs Bacteria vs Archaea
Consider the Following:
- Some diseases can be traced back to organelle lack / malformation. For example, inclusion-cell (I-cell) disease occurs due to a defect in the Golgi. In order to mark enzymes that should be sent to lysosomes to help degrade unwanted molecules, the Golgi has to bind them with a mannose 6-phosphate tag, like a shipping label. However, in patients with I-cell disease, one of the proteins that make this tag is mutated, and cannot do its job, like a broken label machine. This means that proteins cannot be targeted to lysosomes. These untagged proteins are the enzymes that are responsible for chopping up other proteins. What happens is the inactivated enzymes end up being sent outside the cell, while lysosomes clog up with undigested material. This disease is congenital, and usually fatal before patients reach 7 years of age.
- An interesting idea is that mitochondria can be used to trace maternal ancestry. Since mitochondria are self-replicating and have their own DNA, they are not determined by the genes found in the nucleus. Instead, your mitochondria have developed from the mitochondria present in the female ovum (egg) that you developed from. Defects in mitochondrial DNA cause hereditary diseases that pass only from mother to children.