Difference between revisions of "2013 Group 3 Project"

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[[File:The_relationship_between_the_Golgi_and_microtubules.png]]
 
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==What was previously assumed about how GA participated during cell division==
 
  
 
==Morphology of GA prior to cell division==
 
==Morphology of GA prior to cell division==
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It was once theorised that the Golgi apparatus could be formed de novo within daughter and mitotic cells. It has since been discovered that in animal cells, the organelle cannot be synthesised de novo and thus, must divide when a cell divides (1). Through cytochemical (2) and immunofluorescence (3) light microscopy, it has been shown that the Golgi would undergo breakdown early on in mitosis, giving rise to many Golgi fragments (4). These fragments (in the form of small tubules and vesicles) would be dispersed throughout the cytoplasm at random. The partitioned Golgi would segregate into even groups and end up in the daughter cells to serve as a template to new Golgi apparatuses(5).
 
It was once theorised that the Golgi apparatus could be formed de novo within daughter and mitotic cells. It has since been discovered that in animal cells, the organelle cannot be synthesised de novo and thus, must divide when a cell divides (1). Through cytochemical (2) and immunofluorescence (3) light microscopy, it has been shown that the Golgi would undergo breakdown early on in mitosis, giving rise to many Golgi fragments (4). These fragments (in the form of small tubules and vesicles) would be dispersed throughout the cytoplasm at random. The partitioned Golgi would segregate into even groups and end up in the daughter cells to serve as a template to new Golgi apparatuses(5).
 
==the GA can't be synthesized within a cell de novo, so how is it that daughter cells contain a GA?==
 
 
==does the GA's function relate to its behavior during mitosis==
 
  
  

Revision as of 13:07, 9 May 2013

2013 Projects: Group 1 | Group 2 | Group 3 | Group 4 | Group 5 | Group 6 | Group 7


Golgi Apparatus

Introduction

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. [1]

Behavior of the Golgi during Mitosis

Despite being one of the earliest organelles to be identified and studied, there are still grey areas concerning the division of the Golgi Apparatus. Some existing models of division for the Golgi suggest that it interacts with the endoplasmic reticulum during several points throughout cell division. This is due to their structural similarities during the interphase stage of mitosis in mammalian cells. Both consist of interconnect membrane networks and studies have found that both Golgi and ER proteins can be found together in bound vesicles. An experiment conducted by Jesch SA et. al. compares the distribution of the two organelles during interphase using innumnoflourecence microscopy, velocity gradient fractionation and density gradient fractionation. They concluded that the Golgi and the ER do not combine and furthermore that mitotic cells are unable to facilitate the fusion of the two. Instead the Golgi dismantles directly into vesicles and disperses equally throughout the dividing cell so that the resultant daughter cells will contain the necessary constituents.[2]

How does the Golgi differ from other organelles?

Where GA is located in cells

Structure

The Golgi apparatus is a relatively large organelle and thus one of the easiest cell structures to study in detail [3]. 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 (3). 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 (6).

Overall, the Golgi apparatus is made of 4-8 flattened, membrane-bound sacs that are stacked upon one another [4]. 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 (5). 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 [4].

function

history

Stained Golgi.png The relationship between the Golgi and microtubules.png


Morphology of GA prior to cell division

morphology during each part of cell divisions

how the above process differs in other organisms

limitations of current models

Why the GA participates in cell division differently compared to other membrane bound organelles

It was once theorised that the Golgi apparatus could be formed de novo within daughter and mitotic cells. It has since been discovered that in animal cells, the organelle cannot be synthesised de novo and thus, must divide when a cell divides (1). Through cytochemical (2) and immunofluorescence (3) light microscopy, it has been shown that the Golgi would undergo breakdown early on in mitosis, giving rise to many Golgi fragments (4). These fragments (in the form of small tubules and vesicles) would be dispersed throughout the cytoplasm at random. The partitioned Golgi would segregate into even groups and end up in the daughter cells to serve as a template to new Golgi apparatuses(5).


--Mark Hill (talk) 10:00, 4 April 2013 (EST) I do not see even sub-headings listed on the project page?

References

  1. <pubmed>PMC2106267</pubmed>
  2. <pubmed>PMC25291</pubmed>
  3. <pubmed>9865849</pubmed>
  4. 4.0 4.1 <pubmed>19866649</pubmed>


Links

Golgi Apparatus Maintains Its Organization Independent of the Endoplasmic Reticulum

Partitioning of the Golgi Apparatus during Mitosis in Living HeLa Cells

Golgi biogenesis



2013 Projects: Group 1 | Group 2 | Group 3 | Group 4 | Group 5 | Group 6 | Group 7

Dr Mark Hill 2013, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G