Golgi Apparatus / Complex [Structure, Functions, Products]

Structure of Golgi Apparatus

Under the electron microscope, the Golgi apparatus is seen to be composed of stacks of flattened structures that contain various vesicles including secretory granules. The Golgi complex is morphologically very comparable in both plant and animal cells.

However, it is exceptionally pleomorphic: in some cell types it appears compact and restricted, in others spread out and reticular (net-like). Typically, however, the Golgi complex looks like a complicated selection of interconnecting tubules, vesicles, and cisternae.

A.Cisternae

The simplest unit of the Golgi complex is the cisterna. Cisternae (about 1 μm in size) are central, flattened, plate-like, or saucer-like closed compartments that are kept in parallel packages or stacks one above the other.In each stack, cisternae are separated by an area of 20 to 30 nm which might consist of rod-like elements or fibers.

Each stack of cisternae forms a dictyosome which might consist of 5 to 6 Golgi cisternae in animal cells or 20 or more cisternae in plant cells. Each cisterna is bounded by a smooth unit membrane (7.5 nm thick), having a lumen varying in width from about 500 to 1000 nm. The margins of each cisterna are gently curved so that the entire dictyosome of the Golgi apparatus takes on a bow-like appearance. The cisternae at the convex end of the dictyosome make up proximal, forming, or cis-face, and cisternae at the concave end of the dictyosome make up the distal, growing or trans-face.

B.Tubules

A complicated variety of associated vesicles and anastomosing tubules (30 to 50 nm diameter) surround the dictyosome and radiate from it. In fact, the peripheral area of the dictyosome is fenestrated (lace-like) in structure.

C.Vesicles

The vesicles (60 nm in size) are of three types:

• (i) Transitional vesicles are small membrane-limited vesicles which are thought to form as blebs from the transitional ER to move and converge to the cis face of Golgi, where they coalesce to form new cisternae.
• (ii) Secretory vesicles are varied-sized membrane-limited vesicles that release from margins of cisternae of Golgi. They, typically, present in between the growing or maturing face of Golgi and the plasma membrane.
• (iii) Clathrin-coated vesicles are spherical protrusions, about 50 μm in size, and with a rough surface. They are present at the periphery of the organelle, typically at the ends of single tubules, and are morphologically rather distinct from the secretory vesicles. The Clathrin-coated vesicles are understood to play a role in intracellular traffic of membranes and of secretory items, i.e., in between ER and Golgi, along with, between the GELR area and the endosomal and lysosomal compartments.

 

Golgi Apparatus Functions

The Golgi apparatus has lots of discrete functions. But all functions are related to moving molecules from the endoplasmic reticulum to their last location and customizing particular products along the way. The numerous sacs of the Golgi serve as different chambers for chemical reactions. As the products of the endoplasmic reticulum relocation through the Golgi apparatus, they are continuously transferred into new environments, and the reactions that can occur are different.

In this way, an item can be given modifications, or multiple items can be combined to form big macromolecules. The many sacs and folds of the Golgi apparatus enable numerous reactions to take place at the same time, increasing the speed at which an organism can produce products.

Tagging Cellular Products

Regardless of the item, the vesicles consisting of the product move from the endoplasmic reticulum and into the cis face of the Golgi apparatus. In layman’s terms, this is the side facing the endoplasmic reticulum. The side outermost from the endoplasmic reticulum is referred to as the trans face of the Golgi apparatus, and this is where products are headed.

After having any modifications or additions to their structure, the items are packaged in vesicles and tagged with markers that suggest where the vesicle needs to end up. These tags can be molecules, such as phosphate groups, or unique proteins on the surface of the vesicle. As soon as tagged, the vesicle is excreted from the Golgi complex, on its way to its final location.

Finalizing Cellular Products

In secretory cells, or cells that produce big amounts of a substance that your body needs, the Golgi complex will be large. Consider the cells in your stomach that produce acid. The acid is produced by reactions in the endoplasmic reticulum and is modified as it passed through the Golgi complex. When to the trans side of the Golgi apparatus, the acid is packaged in a vesicle and sent towards the cell’s surface. As the vesicle joins with the plasma membrane, the acid is released into the stomach, so it can absorb your food.

Golgi Complex in Plant Cells

While this article primarily discusses the operation of the Golgi apparatus within animal cells, plant cells also have a Golgi apparatus. In fact, plant cells may consist of hundreds of these organelles.

Within plant cells, the Golgi apparatus serves the additional function of synthesizing the major polysaccharide molecules which help in the formation of the cell wall. To do this, plants frequently have a lot more Golgi bodies than an animal cell.

Even more, plant cells do not include lysosomes. These digestive organelles are replaced in the plant with the central vacuole, which serves as a large lysosome along with an organelle to store water. Hence, lots of vesicles from the Golgi bodies of plants transfer to the vacuole and fuse their contents with this big organelle.

MCQs

 

FAQs – Golgi Apparatus / Complex [Structure, Functions, Products]