The document discusses the discovery and structure of the Golgi apparatus. It was discovered in 1898 by Italian physician Camillo Golgi and has since been observed under light and electron microscopes. Under electron microscopy, it appears as a stack of flattened sacs called cisternae, along with peripheral tubules and vesicles. The cisternae vary in number between cell types and the Golgi complex plays an important role in processing and transporting materials within the cell.

2. DISCOVERY
 THE GOLGI APPARATUS IS NOTICIBLE WITH BOTH LIGHT AND
ELECTRONE MICROSCOPE. IT ALSO CALLED AS GOLGI
COMPLEX .
 THE GOLGI COMPLEX WAS DISCOVERED BY AN ITALIAN
PHYSICIAN CAMILLO GOLGI IN 1998 DURING THE
INVESTIGATION OF NERVUS SYSTEM.
 ITS ELECTRON MICROSCOPIC STRUCTURE WAS DESCRIBED BY
DALTON AND FELIX IN 1954.

3. LOCATION
 The golgi apparatus is present in all Eukaryotic cells and absent in
prokaryotes.
 The golgi apparatus is specially extensive in the secretory cells.
 It is absent in few cell type, such as the mammalian RBCs, sperm cells of
Bryophytes and sieve tubes of plants.
 A cell may have one large golgi complex or severe very small ones. It
occupies different positions in different kind of cells.
 In secretory and absorptive cells, it usually lies between the nucleus.
 Plant cells usually have several small golgi complex , called dictyosomes

4. STRUCTURE OF GOLGI COMPLEX
 Golgi bodies varies in size and form in different cell
types, but usually has similar organization for kind
of cells. For example it is well developed in
secretory and nerve cells but is rather small in
muscle cells.
 Electron microscope show it as a central stack of
flattened sacs or cisternae and many peripheral
tubes and vesicles.

5. CISTERNAE
 The cisternae vary in number from 3-7 in most animal cells and from 10-24 in plant cells.
 The cisternae may be flat but are often curved.
 Golgi complex has a distinct polarity , the two poles are called cis face and trans face,
which act respectively as the receiving and shipping departments.
 Convex side of stack – forming face(cis face )
 Concave side of stack - maturity face(trans face)
 Secretory materials reach the golgi complex from smooth endoplasmic reticulum (SER) by
way of transport vesicles which bud off from SER with fuse with golgi cisternae on the cis
face.
 From the trans face secretory vesicles arises that carry the processed material to their
destination.
 TUBULES: small, round tubules arises from the periphery of the cisternae. Some of
these enlarged at their end to form vesicles.
 Vesicles : the vesicles lie near the ends and concave surface of the golgi complex.

6. FUNCTIONS
 Formation of secretory vesicles.
 Synthesis of carbohydrates.
 Formation of glycoproteins.
 Formation of lipoproteins.
 Addition to cell membrane.
 Membrane transformation.
 Formation of cell wall.
 Formation of lysosomes.
 Acrosome formation.
 Storage of secretions.
 Absorption of materials.

7. RIBOSOMES
 Term ribosomes was coined by G.Palade(1955).
 Also called ‘palade particles’ Found in both prokaryotes & eukaryotes(
except sperm & RBC)
 Reported inside the matrix of mitochondria & plastids also.
 No. of ribosomes depend upon the RNA contents & basophilic nature of
the cell.
 Sites of protein synthesis so called protein factories.

8. Types :
On the basis of sedimentation coefficient, ribosomes are of 2 types:
(A ) 70S Ribosomes:
Found in prokaryotes.
(B)80S Ribosomes:
Found in cytoplasm of eukaryotes.

10.  Chemical composition:
 70S 60-65% r-RNA
50S subunit :23S rRNA,5S rRNA
30S subunit:16S rRNA
 80S ribosome:
 60S subunit:28S rRNA,5SrRNA,5.8SrRNA
 40S subunit:18SrRNA
 In each ribosomal subunit rRNA is in the form of highly folded filament, different types of proteins are
adhered to it.
 60% rRNA is in double helix form.
 Most abundant nitrogen bases are guanine & cytosine.

11. FUNCTIONS:
These are sites where specific no. & types of
acids are linked in a specific sequence form a
polypeptide chain, so these are protein factories of
the cell.
Free ribosomes are involved in synthesis of
intracellular proteins.
ER-bound ribosomes synthesize proteins which
intercellularly.

13. introduction
 The plastid (Greek: plastós: formed, molded) is a
major organelle found In the cells of plants and algae.
 Plastids are the sites of manufacture and storage of starch, fatty acids,
cuticle, epicuticular wax and terpenes which can be used for
producing energy and important chemical compounds used by the
cell. Therefore known as kitchen of plant cell.
 Plastids often contain pigments used in photosynthesis, and others
which determine the cell's color.
 All plastids are derived from proplastids which are present in
the meristematic regions of the plant. Proplastids and young
chloroplasts commonly divide by binary fission.

14.  In plants, plastids may differentiate into several forms, depending upon which
function they play in the cell. Undifferentiated plastids (proplastids) may develop into
any of the following variants:
 Chloroplasts (green) plastids:for photosynthesis
 Chromoplasts (coloured) plastids: for pigment synthesis and storage
 Leucoplasts: colourless plastids: for monoterpene synthesis; leucoplasts sometimes
differentiate into more specialized plastids:
 Amyloplasts: for starch storage and detecting gravity
 Elaioplasts: for storing fat
 Proteinoplasts: for storing and modifying protein
 Tannosomes: for synthesizing and producing tannins and polyphenols
 Depending on their morphology and function, plastids have the ability
to differentiate, or redifferentiate, between these and other forms.

15. Plastids
chromoplasts amyloplasts chloroplasts

16.  The proplastid contains a single nucleoid located in the centre
of the plastid. The developing plastid has many nucleoids
located at the periphery of the plastid.
 Plastid DNA (plastome) is circular 75–250 kilobase. The number
of plastome per plastid is variable, ranging from more than 1000
to 100 or fewer in cells. Plastid multiply by divisions.
 The plastome contains about 100 genes encoding ribosomal
and transfer ribonucleic acid (rRNAs and tRNAs) as well
as proteins involved in photosynthesis and transcription and
translation of plastid’s genes.

17. Structure
 Chloroplasts are located in the parenchyma cells of plants as well as in
autotrophic algae. They are oval-shaped organelles having a diameter of 2
- 10 µm and a thickness of 1 - 2 µm. Although their dimensions are almost
similar in all plants, the algal chloroplasts show a variation in their size as
well as shape.
 Envelope: The chloroplast envelope is double-membrane
structure comprising an outer and an inner membrane. Each
of these membranes is a phospholipid bilayer, and is 6 - 8 nm
thick. A 10 - 20 nm thick space present between the two
membranes is known as intermembrane space.

18. Chloroplasts in plants

19.  Stroma: The aqueous matrix present inside the double-membrane
envelope is called the stroma. The stroma is especially rich in
proteins, and contains several enzymes necessary for vital cellular
processes.
 Thylakoids: two membranes that form the envelope, chloroplasts
contain a third internal membrane system called thylakoid
membrane. The internal portion of the thylakoid is called the
thylakoid lumen, and contains plastocyanins and other molecules
required for the transport of electrons.
 Grana: Some of the thylakoids are arranged in the form of discs
stacked one above the other. These stacks are termed grana.


20. FUNCTIONS.
1. Protein synthesis
2. Starch storage
3.oxygen supply
4.photosynthesis
5. Photorespiration

21. Leucoplasts (leukós „white“) are non-pigmented plastids.
 Lacking pigments, leucoplasts are colourless, so they are predictably located
non-photosynthetic tissues of plants. They may become specialized for bulk storage
of starch, lipid or protein and are then known as amyloplasts, elaioplasts,
or proteinoplasts respectively.
 In many cell types leucoplasts have wide range of essential biosynthetic functions,
including the synthesis of fatty acids, many amino acids.
 In general, leucoplasts are much smaller than chloroplasts and have a variable
morphology, often described as amoeboid. Extensive networks of stromules
interconnecting leucoplasts have been observed in epidermal cells of roots, hypocotyls,
and petals, and suspension culture cells of tobacco.

22. Chromoplasts
 They are found in fruits, flowers, roots, and stressed and aging leaves,
and are responsible for their distinctive colors. This is always
with a massive increase in the accumulation of carotenoid pigments.
 Chromoplast are heterogeneous organelles responsible for pigment
synthesis and storage in specific photosynthetic eukaryotes.

23.  Chromoplasts synthesize and store pigments such as orange carotene,
yellow xanthophylls, and various other red pigments. As such, their color
varies depending on what pigment they contain.
 The main evolutionary purpose of chromoplasts is probably to
attract pollinators or eaters of colored fruits, which help disperse seeds.
However, they are also found in roots such as carrots and sweet potatoes.
They allow the accumulation of large quantities of water-insoluble
compounds in otherwise watery parts of plants.
 When leaves change color in the fall, it is due to the loss of
green chlorophyll, which unmasks preexisting carotenoids. In this case,
relatively little new carotenoid is produced.

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