Here is a compilation of term papers on ‘Golgi Complex’ for class 9, 10, 11 and 12. Find paragraphs, long and short term papers on ‘Golgi Complex’ especially written for school and college students.
Term Paper on Golgi Complex
Term Paper Contents:
- Term Paper on the Introduction to Golgi Complex
- Term Paper on the Origin of Golgi Complex
- Term Paper on the Occurrence of Golgi Complex
- Term Paper on the Morphology of Golgi Complex
- Term Paper on the Detailed Structure of Golgi Complex
- Term Paper on the Golgi Complex is Structurally and Biochemically Polarised
- Term Paper on the Chemical Composition of Golgi Complex
- Term Paper on the Functions of Golgi Complex
Term Paper # 1. Introduction to Golgi Complex:
In 1898 by means of a silver staining method, Golgi discovered a reticular structure in the cytoplasm. The name “Golgi apparatus”, generally given to this structure, is confusing because it suggests a definite relationship with the physiologic processes of the cell.
Today it seems more appropriate to use the name “Golgi substance” or “Golgi complex to refer to this material that has special staining properties. Because, its refractive index to similar to that of the matrix, the Golgi complex is difficult to observe in living cells. The use of the electron microscope has provided a distinct image of this component, and its submicroscopic structure has been revealed.
For years the Golgi complex was thought to be an artifact of various fixation and staining procedures. In other words, many scientists believed that the structure observed during numerous microscopy procedures and termed the Golgi did not actually exist in the living cell. Guilliermond, Parat Walker and Allen, doubts arose with regard to the existence of Golgi complex.
The different lines of objections against the existence of Golgi complex are as follows:
(a) Nothing corresponding to the Golgi elements exists in the living cells, what appears Golgi bodies in the processed cells are myeline figures, produced by the action of cytological reagents or lipids, hove, ever, believe in the existence of Golgi bodies in the germ cells but no such things in the somatic cells.
(b) The Golgi apparatus of the fixed material is produced by the deformation and metallic impregnation of several unrelated cytoplasmic bodies.
(c) The dictyosome or acroblasts of male germ cells homologised with the Golgi apparatus of nerve cells. Gatenby, Bowen and Hirschler, Parol believed that they are nothing but the modified mitochondria.
(d) The Golgi apparatus is a stack of the smooth endoplasmic reticulum.
Answer to the Objections:
(a) In a number of cells those bodies have been studied in vivo or in vitro with phase contrast microscopy.
(b) The Golgi bodies have been separated by centrifugal fractionation of homogenised cell. The objection of artifact is discarded on the basis that artifact cannot show the pattern of the same type as shown by these bodies.
(c) Their ultra-structure has been recently studied with the electron microscope by Sjostrand and flanzon and Dalton and Felix.
(d) Dictyosomes of male germ cells which are impregnated with silver and osmium have same type of chemical composition as the Golgi apparatus of somatic cells.
(e) According to Srivastava dictyosomes in male germ cells, are favourable materials for the study of Golgi bodies even under the light microscope.
(f) The idea that the dictyosomes are modified, mitochondria has been discarded on the basis of biochemical tests:
(i) The dictyosomes of male germ cells contain appreciable quantity of polysaccharides, it is also present in the somatic Golgi bodies but not found in mitochondria. Similarly alkaline phosphatase is associated with Golgi bodies, but not found in the mitochondria.
(ii) Tiwari and Broune have found that the distribution of adenosine triphosphatase is localised in mitochondria but not in Golgi bodies. In the same way succinic dehydrogenase and cytochrome oxidase are noted from the mitochondria, but not in the Golgi bodies.
(g) The statement that the Golgi bodies of neuron are nothing but endoplasmic reticulum is discarded on the basis of electron microscopic structure and the width of Golgi membrane is different from that of the endoplasmic reticulum.
In concluding the controversy of the Golgi apparatus, it should be pointed out that Baker and these students were the last to accept the reality of the Golgi apparatus when Baker wrote “The author accepts, after long hesitation, the view that the Golgi apparatus in the neurons of vertebrates corresponds with the organelle of the same name, in other cells”.
Term Paper # 2. Origin of Golgi Complex:
Three different sources have been proposed from which new Golgi complex may arise:
a. From Endoplasmic Reticulum:
Essner and Novikoff and Beams and Kessel have proposed that the Golgi cisternae arise from the ER. The rough endoplasmic reticulum after synthesizing specific proteins loses ribosomes and changes into smooth ER. Small transitory vesicles pinch off from smooth ER. These migrate to dictyosome. On reaching the forming face of dictyosome these fuse to form new cisternae and thus contribute to its growth.
By the fusion of these vesicles new cisternae are formed, continuously on the forming face and on the maturing face the old cisternae break down into secretory vesicles. Thus Golgi exhibits a phenomenon of membranous flow.
b. From Nuclear Membrane:
Figure 5.6: Origin of Golgi Complex by the Division of Pre-Existing One
Bouch described the origin of Golgi from outer membrane of nuclear envelope in brown algae. Vesicles are pinched off from outer nuclear membrane which fuses to form cisternae on the forming face of dictyosome.
Presence of zones of exclusion in relation with smooth ER or nuclear membrane, the occurrence of zones of exclusion in dormant seeds of higher plants and the formation of ditcyosome from these zones in germinating seeds provide evidence in support of the above two theories about the origin of dictyosome.
c. By the Division of Pre-Existing Dictyosome:
It has been observed that during cell division in both plants and animals, the number of dictyosomes increases and the number of dictyosomes in each daughter cell just after division is almost equal to the number in the parent cell prior to division. From this and other direct observations on the dividing cells, it has been presumed that dictyosomes also divide during cell division.
Term Paper # 3. Occurrence of Golgi Complex:
The Golgi complex occurs in all cells except the prokaryotic cells (viz., mycoplasma, bacteria and blue green algae) and eukaryotic cells of certain fungi, sperm cells of bryophytes and pteridophytes, cells of mature sieve tubes of plants and mature sperm and red blood cells of animals.
Their number per plant cell can vary from several hundred as in tissues of corn root and algal rhizoids (i.e., more than 25,000 in algal rhizoids), to a single organelle in some algae. In animal cells, there usually occurs a single Golgi complex; however, enveloping oocytes of chordates may contain many Golgi bodies.
Term Paper # 4. Morphology of Golgi Complex:
The morphology of the Golgi complex varies from cell to cell depending upon the type of cell in which they are found.
Two forms of Golgi complex have been observed:
a. Localised Form:
In polarised cells of vertebrates (which have base and apex), Golgi complex occurs singly and occupies a fixed position. It lies between the nucleus and secretory pole. This can be best seen in thyroid cells, in exocrine cells of pancreas and the mucous cells of intestine.
b. Diffused Form:
In some specialised cells of vertebrates (nerve cells and liver cells), in most plant cells and in the cells of invertebrates several units of Golgi complex are found scattered along with the elements of endoplasmic reticulum. Each unit is called a dictyosome. In liver cells there occur as many as 50 dictyosomes per cell and in certain plants cells their number may reach upto hundreds.
Shape of Golgi Complex:
The shape of the Golgi complex is quite variable in different somatic cell types of animals. Even in the same cell there are variations in different functional stages. The shape is, however, constant with each cell type. It varies in form from a compact mass to a disperse filamentous network.
Number:
The number of Golgi stacks per cell varies enormously, depending on the cell type-from as few as one to the hundreds. There is a single large in some cells while in the case of Paramoeba there are two. In Stereomyxa (a species of Amoeba) there are many Golgi complexes.
Nerve cells, liver cells and most plant cells also have multiple Golgi complexes, there being about 50 in liver cells. The Golgi complex can even account for a large fraction of the cell volume in some specialised cells. One example is the goblet cell of the intestinal epithelium, which secretes mucus into the gut; the glycoproteins in mucus are glycosylated principally in the Golgi complex.
Size of Golgi Complex:
The size is likewise very variable. It is large in the nerve and gland cells and small in the muscle cells. In general the Golgi complex is well developed while the cell is in active state. When the cell grows old, the apparatus progressively diminishes in size and disappears.
Position of Golgi Complex:
The position of the Golgi complex is relatively fixed for each cell type. In the cells of octodermal origin, the Golgi complex is polarised from the time of the embryonic state sweep the nucleus and the periphery. In the secretory exocrine cells that have in general a typical polarisation the Golgi complex is found between the nucleus and the secretory pole.
In the endocrine glands the polarity of this organoid is variable, except in the thyroid, where it is oriented towards the centre of the follicle. In the younger cells and often in the older ones it lies most commonly at one side of the nucleus but certain cases may completely surround it. In ganglionic cells the mouse the position is perinuclear.
Term Paper # 5. Detailed Structure of Golgi Complex:
Dalton and Felix described the Golgi complex in the Jidymis of the rat after taking the first electron microphs.
The following description of the Golgi complex is found as follows:
a. Cisternae:
The cisternae or saccules are similar to the smooth surface ER, and appear in section as stacks of closely spaced membrane-delimited sacs. The number of saccules varies from about 4 to 8 in most animal and plant cell types. In Euglena, the number may go upto 20. The membrane of the saccule is roughly 60 to 70 Å in thickness which encloses a cavity about 150 Å wide whose edges are often dilated.
According to most authors, there are two well defined faces of the cisternae, i.e., convex and the concave; the latter is generally referred to as e mature or forming or distal face and the convex side is assumed to be the immature or excite or proximal face, the cisternae lie in parallel array are separated from each other by a space of about 200 to 300 Å.
What holds them together is not yet known but in few cells a thin layer of electron opaque, sometimes dense material is seen between the saccules which at certain regions are more prominent to which Amos and Grimstone applied the term nodes. Mollenhauer et al. explored in some detail intercisternal elements and plaques in certain plant Golgi complex.
b. Tubules:
From the peripheral area of cisternae arise a complex, anastomosing flat network of tubules of 300 to 500 Å diameters. Clowes and Juniper have compared this tubular network to disc of lace.
c. Vesicles:
The vesicles are small droplet-like sacs which remain attached to tubules at the periphery of the cisternae.
They are of following two types:
i. Smooth Vesicle:
The smooth vesicles are of 20 to 8m 0μ diameter. They contain secretory material (so often are called secretory vesicles) and are budded off from the cisternal tubules within the net. Often more than one tubule connects to, and presumably fill, a single forming vesicles.
ii. Coated Vesicles:
The coated vesicles are spherical protuberances, about 50 mμ in diameter and with a rouge surface.
They are found at the periphery of the organelle, usually at the end of single tubules, and are morphologically quite distinct from the secretory vesicles. Their function is unknown.
d. Golgian Vacuoles:
These are large rounded sacs present on the maturing face of Golgi. These are formed either by the expanded cisternae or by the fusion of secretory vesicles. The vacuoles are filled with some amorphous or granular substance.
Term Paper # 6. The Golgi Complex is Structurally and Biochemically Polarised:
The Golgi complex has two distinct faces:
i. A cis, or forming face and
ii. A trans, or maturing face.
The cis face is closely associated with a smooth transitional portion of the rough ER. In secretory cells, the trans face is the face closest to the plasma membrance; here, the large secretory vesicles are found exclusively in association with the trans face of a Golgi stack, and the membrane of a forming secretory vesicle is often continuous with that of the trans face of the last (‘transmost”) cisterna.
In contrast, the small Golgi vesicles are localised more evenly along the stack. Proteins are commonly thought to enter a Golgi stack from the ER on the cis side and to exit far multiple destinations on the trans side; however, neither their exact path through the Golgi complex nor bow they travel from cisterna to cisterna along each stack are known.
The two faces of the Golgi complex are biochemically distinct. For example, a variation in the thickness of the Golgi membranes can be detected across the stack in certain cases, with those at the cis side being thinner (ER-like) and those at the trans side being thicker (plasma- membrane like).
More striking are the results obtained when certain histochemical tests are used in conjunction with electron microscopy to localise particular proteins within the Golgi complex. Some of these tests reveal membrane-bound enzyme activities that show a distinct polarity in their localisation within the Golgi stack.
A particularly intriguing biochemical finding was the discovery that lysosomal enzymes, such as acid phosphatase, are concentrated with the trans-most cisterna of the Golgi stack and within some of the coated vesicles nearby. This suggests that specific vesicles leaving for lysosomes are assembled in this region.
Secretory proteins are found by histochemical methods in all of the stacked cisterna, even though the large secretory vesicles in which these products are concentrated and associated only with the trans-most Golgi cisterna.
Term Paper # 7. Chemical Composition of Golgi Complex:
Regarding the chemical composition of Golgi complex, it has been demonstrated that the following substances are present:
a. Phospholipids:
Phospholipids composition of Golgi membranes is intermediate between those of endoplasmic membranes and plasma membranes.
b. Proteins and Enzymes:
Golgi complex from different plant and animal cells show great variations in the protein and enzyme contents. Some of the enzymes are ADPase, ATPase, CTPase, NADPHcytochrome-C-reductase, glycosyl transferases, galactosyl transferase, thiamine pyrophosphate etc.
c. Carbohydrates:
Both plant and animal cells have some common carbohydrate components, like glucosarine, galactose, glucose mannosa, and fructose. Plant Golgi lack sialic acid, but occurs in high concentration in rat liver. Some carbohydrate like xylase and arabinose are present in plant cell only.
d. Vitamin C:
The function of vitamin C stored in the Golgi complex has been shown by Tomitte. According to him Golgi complex stores vitamin C and liberates it slowly into the cytoplasm it sufficient amount to prevent- oxidation of the cell products.
Term Paper # 8. Functions of Golgi Complex:
i. Formation of Acrosome during Spermiogenesis:
During the maturation of sperm the Golgi complex plays a in the formation of acrosome. In early stages, the Golgi appears as a spherical body, comprising cisternae arranged in paralled stacks and numerous small vesicles. The later always pinched off from the cisternae. As development proceeds, the Golgi complex becomes irregular in shape and large vacuoles are formed by dilations of cisternal sacs.
In the centre of these large vacuole or vacuoles is/are present a dense granule, the proacrosomal granule. This granule which is derived from Golgi complex continues to grow within the vacuole by a process known as accretion. This vacuole and granule approaches the anterior pole of the nuclear membrane, constituting acrosomal granule.
With the elongation of the spermatid, the acrosomal vesicle spreads over the nuclear surface and finally collapses with the nuclear membrane, forming the cap material. The acrosomal granule becomes the acrosome which lies at the apex of the nucleus and apparently comprises certain enzymes involved in the process of fertilisation.
ii. Synthesis and Secretion of Polysachharides:
Studies on goblet cell by autoradiography and electron microscopy have established the inter-relationship between protein synthesis, carbohydrate addition and sulphation. The goblet cells of the colon produce mucigen. This secretory material contains a large proportion of carbohydrate. The Golgi complex is found just above the nucleus.
Towards the free surface of the cell are gradually enlarging mucigen granules. The proximal cisternae of the Golgi complex do not show any welling, but at some distance across the stack the distal cisternae are quite suddenly converted into mucigen granules. The distal cisternae continually convert into mucigen granules very 2-4 minutes. New proximal cisternae are formed in compensation.
iii. Role in Secretion:
Golgi complex is considered to play some role in the secretory functions of a cell. But the question is this that they are secreting or synthesizing some substances themselves or they are simply a store house in which the secretory products which are secreted somewhere else in the cell, is simply stored and concentrated.
From the studies of Palade et al. 1962 this secretory is now well defined and includes four steps in case of pancreatic acinar cells and they are:
(a) The in-corporation of amino-acids into protein at the surface of rough endoplasmic reticulum.
(b) Transfer of these nascent secretory proteins into the cisternae of rough endoplasmic reticulum.
(c) The intracellular transport of these proteins to the Golgi complex.
(d) The migration of zymogen granules towards the apex of the cell where they discharged into lumens.
iv. Role of Golgi Body in Oogenesis:
Srivastava has given a brief review on the Golgi complex during oogenesis.
According to Afzelius, the Golgi complex of a sea-urchin egg, as seen under electron microscope, consists of stacks of lamellae forming walls of flat pouches, which may occasionally be swollen. There are some indications of transverse divisions of these bodies. Satelo and Solelo and Porter have described the Golgi complex in rat-ovum as seen under the electron microscope and found juxtra nuclear localisation of this organelle in early oocytes.
In the next stage, these resolve into fragments and in the third stage, these move towards the cortex. In all these cases, their structures remain to be of closely packed arrays of slender, double profiles (flattened sacs) and spherical vesicles. In the early oocytes the complex is compactly organised. In later stage, discrete bundles of profiles, surrounded by small vesicles are found scattered in the cortical zone. In the early oocytes, the Golgi complex and centrosome are closely associated.
v. Absorption of Compounds:
Hirsch et al., have discovered that, when iron sugar is fed to an animal, iron becomes absorbed on Golgi complex (Kedrowsky). Van Teel has shown that Golgi systems also absorb compounds of copper and gold. Kedrowsky has shown that Golgi complex of Opalina can absorb bismutose (compound of albumin and bismuth) and protargol (compound of albumin and silver). Thus, Kirkman and Severing-haus state that Golgi complex acts as a condensation membrane for the concentration of products into droplets or granules.
vi. Plant Cell Wall Formation:
The cell walls of plants are made up of fibrils which predominantly contain polysaccharides, along with some lipids and proteins. During cytokinesis a cell plate is formed between the two daughter nuclei, and has around it a membrane which later becomes the plasma membrane of the daughter cells. There is clear evidence that the polysaccharides are formed in the Golgi complex and transferred to the new cell wall which is laid down while the cells are still growing.
Substances like pectins and hemicelluloses, which form the matrix of the cell plate separating the plasma membranes, are also contributed by the Golgi complex.
vii. Formation of Intracellular Crystals:
In the marine isopod, Limnoria ligmorum, there are present mid-glands whose cells consist crystals. These range up to 30A° in length and 15A° thick. It is been proved that these crystals are formed by Golgi complex and are known to contain protein and iron. They are without enclosing membrane and usually spheroidal in shape. They are concerned with the secretory activity.
viii. Milk Protein Droplet Formation:
In the lactating mammary gland of mice are produced protein droplets which are related with Golgi complex. These droplets usually open on to the cell surface by the fusion of their enclosing membrane with the plasma membrane.
ix. Formation of Lysosomes and Vacuoles:
Primary lysosomes are formed from the Golgi membranes the same way as the secretory vesicles. There is good evidence that dictyosomes accumulate hydrolytic enzymes in their more mature regions. Some vacuoles in plant cells have been found to contain small amounts of hydrolytic enzymes and these are presumed to have been derived from Golgi complex.
x. Pigment Formation:
In many mammalian tumour and cancer cells the Golgi complex has been described as the site of origin of pigment granules (melanin).
xi. Regulation of Fluid Balance:
A homology has been suggested between the Golgi complex and the contractile vacuole of lower Metazoa and Protozoa. The contractile vacuole expels surplus water from the cell. In certain Protozoa the Golgi complex is also concerned with regulation of fluid balance.