2013 Group 3 Project
The Golgi Apparatus discovered in 1897 by physician Camillo Golgi is a vital cellular organelle which is found in almost all eukaryotic cells. It is found in the cytoplasm and facilitates the formation and direction of membrane bound vesicles, mainly formed from proteins directed from the rough endoplasmic reticulum before they reach the plasma membrane. The Golgi is capable of regulating cellular transport and secretion depending on the volume and density of the vesicles and their contents. Structurally, it consists of a series of stacked components of cisternae and has two identified faces- a cis face and a trans face. 
The Golgi apparatus is a relatively large, membrane-bound organelle and thus one of the easiest cell structures to study in detail . The organelle is located nearby the cell nucleus and is closely associated with the endoplasmic reticulum. By observing via metallic impregnation, it can be seen through phase contrast microscopy that the Golgi has a convoluted, dense and “ill-formed” morphology . Initial studies have shown that the organelle has great variance in its form dependent on the type of cell it is in as well as the state of activity that the cell is in. There are roughly around 40-100 Golgi apparatus ‘stacks’ within a mammalian cell .
Overall, the Golgi apparatus is made of 4-8 flattened, membrane-bound sacs that are stacked upon one another . These are known as cisternae. The Golgi also includes associated nearby vesicles. Each cisterna primarily contains products from the endoplasmic reticulum, which enter the Golgi at the cis face – the end that is closest to the ER and accepts incoming vesicles . The cis face is where new cisternae are formed. The products eventually pass through two more functional regions (medial Golgi and endo Golgi networks) and then are exported via outgoing vesicles at the trans face of the organelle. The trans face is where formed proteins are sent off and is the face furthest away from the ER. There is a constant and relatively consistent distance kept between cisternae of the Golgi apparatus .
Golgi apparatus is considered to be essential membrane-bound organelle in eukaryotic cells that sums all plant, animal and fungi life . It's physical structure is a composition of dozens of flattened cristernae that has been brought together and flattened with fenestrated rims. Golgi has a primary function of modifying and packaging proteins and lipids into several transport carriers to be able to send them to their proper locations. Proteins such as secretory or trans-membrane proteins are delivered from the endoplasmic reticulum (ER) to the cis-Golgi network. Consequently, the Golgi act as a series of transportation canal where cargo molecules travel via different Golgi cristernae where residential enzymes modify and post-transitionally process them.
|1898||The organelle was first described by Camillo Golgi. It was observed via treatment of tissue with potassium dichromate and osmic acid followed by silver nitrate. He termed the organelle 'appareil reticulaire interne' (internal reticular apparatus) and documented his findings in 'Arhives Italliennes de Biol 1898'.|
|Up to 1950s||The term 'Golgi apparatus' was coined in 1910, and its first appearance in scientific literature was in 1913Cite error: Closing
Morphology of GA prior to cell division
flattened membrane-bound structures approxi- mately 1 m m long, also termed Golgi cisternae. Between two and five cisternae are aligned in a parallel manner to form a Golgi stack.
The Golgi stacks are polarized in a cis / trans fashion
morphology during each part of cell divisions
limitations of current models
A key problem with this line of reasoning is that micro- injection of the identical Sar1p mutant protein (GDP- or GTP- bound form) in interphase cells leads to the fragmentation of the Golgi apparatus into vesicles and tubules very similar to those comprising the MGCs.
This suggests that in itself cessation of transport from the ER is a detrimental factor for the maintenance of the Golgi apparatus and is independent of the localization of Golgi enzymes. One possibility is the requirement for a factor that needs to be transported to a downstream location to regulate maintenance/reassembly of the Golgi apparatus is accumulated in the ER. It is perhaps therefore not possible for normal Golgi reassembly to occur at the end of the mitosis in cells micro-injected with Sar1p DN .
The recycling of Golgi enzymes to the ER observed during interphase could take place to a certain extent during mitosis. More sensitive electron microscopy methods need to be developed to detect endogenous and transfected and epitope-tagged proteins that are expressed at low levels. These enzymes, when present in the ER, could indeed be partitioned in an ER-dependent manner, while others Golgi components, the structural Golgi proteins (see the Introduction), could be partitioned with the MGCs.