PPT ABOUT PLASTIDS

this is one of the best ppt about Plastids

1. PLASTIDS

2. Name: Shuvankar Dutta Class : B. tech (C.S.E) Roll no : 10 Group No: 3 Subject : Biological Science Supervised by: Madhurima Das Power Point Presentation for CA 4 Exam Plastids

3. Definition Plastids are a group of phylogenetically and physiologically-related organelles found in all types of plants and algae. In their roles, the different types of plastids contribute to plant metabolism thus promoting plant growth and development. One of the main characteristics of these organelles is the fact that they have a double membrane. In the cells, plastids are primarily involved in the manufacture and storage of food. They are therefore involved in such processes as photosynthesis, synthesis of amino acids and lipids as well as storage of various materials among a few other functions. Apart from plants and algae, plastids can also be found in a number of other organisms including: Examples: Chromoplasts Chloroplasts Leucoplasts

4. Types of Plastids

5. Types of Plastids An undifferentiated plastid is called a  proplastid . It may develop later into any of the other plastids. Chloroplasts Chromoplasts Leucoplasts Gerontoplasts  

6. Structures Structure of Plastids : Chloroplasts may be spherical, ovoid or discoid in higher plants and stellate, cup-shaped or spiral as in some algae. They are usu­ally 4-6 µm in diameter and 20 to 40 in number in each cell of higher plants, evenly distributed throughout the cytoplasm. The chloroplast is bounded by two lipoprotein membranes, an outer and an inner membrane, with an intermembrane space between them. The inner membrane encloses a matrix, the stroma which contains small cylindri­cal structures called grana. Most chloroplasts con­tain 10-100 grana. Each granum has a number of disc-shaped membranous sacs called grana lamellae or thylakoids (80-120Å across) piled one over the other. The grana are intercon­nected by a network of anastomosing tubules called inter-grana or stroma lamellae. Single thylakoids, called stroma thylakoids, are also found in chloroplasts.

7. Structures Structure of Plastids : Electron dense bodies, osmophilic granules along with ribosomes (70S), circular DNA, RNA and soluble enzymes of Calvin cycles are also present in the matrix of the stroma. Chloroplasts thus have three different mem­branes, the outer, the inner and the thylakoid membrane. The thylakoid membrane consists of lipoprotein with a greater amount of lipids which are galactolipids, sulpholipids , phospholipids. The inner surface of the thylakoid membrane is gra­nular in the organization due to small spheroidal quantosomes . The quantosomes are the photosynthetic units, and consist of two structurally distinct photosystems, PS I and PS II, containing about 250 chlorophyll molecules. Each photosystem has antenna chlorophyll com­plexes and one reaction center in which energy conversion takes place. In higher plants, the pig­ments present are chlorophyll-a, chlorophyll-b, carotene, and xanthophyll. The two photosystems and the components of the electron transport chain are asymmetrically distributed across the thylakoid membrane. Electron acceptors of both PS I and PS II are on the outer (stroma) surface of the thylakoid membrane. Electron donors of PS I are on the inner (thylakoid space) surface.

8. Structures of Plastids

9. Occurrence of Plastids Plastids are thought to be endosymbiotic cyanobacteria. This primary endosymbiotic event is hypothesized to have occurred around 1.5 billion years ago and enabled eukaryotes to carry out oxygenic photosynthesis . Three evolutionary lineages have since emerged in which the plastids are named differently: chloroplasts in green algae and plants, rhodoplasts in red algae and muroplasts in the glaucophytes. The plastids differ both in their pigmentation and in their ultrastructure. For example, chloroplasts in plants and green algae have lost all phycobilisomes, the light harvesting complexes found in cyanobacteria, red algae and glaucophytes, but instead contain stroma and grana thylakoids. The glaucocystophycean plastid—in contrast to chloroplasts and rhodoplasts—is still surrounded by the remains of the cyanobacterial cell wall. All these primary plastids are surrounded by two membranes. In contrast to primary plastids derived from primary endosymbiosis of a prokaryoctyic cyanobacteria, complex plastids originated by secondary endosymbiosis in which a eukaryotic organism engulfed another eukaryotic organism that contained a primary plastid. 

10. Working principle of Plastids All plant cells contain plastids in some shape or form. This roll-call indicates their functional diversity and demonstrates that plastids lie at the very core of plant cellular function .  Plastids are the site of manufacture and storage of important chemical compounds used by the cells of autotrophic eukaryotes. The thylakoid membrane contains all the enzymatic components required for photosyn­thesis. Interaction between chlorophyll, electron carriers, coupling factors, and other components takes place within the thylakoid membrane. Thus the thylakoid membrane is a specialized struc­ture that plays a key role in the capture of light and electron transport. Thus, chloroplasts are the centers of synthesis and metabolism of carbohydrates. They are not only of crucial importance in photosynthesis but also in the storage of primary foodstuffs, particularly starch. Its function largely depends on the presence of pigments. A plastid involved in food synthesis typically contains pigments, which are also the ones responsible for the color of a plant structure (e.g. green leaf, red flower, yellow fruit, etc.). Like mitochondria, plastids have their own DNA and ribosomes. Hence, they may be used in phylogenetic studies.

11. Outcome of Your Study Plastid is a generic name of divergent plant organelles, such as chloroplasts in green leaves, etioplasts in dark grown seedlings and amyloplasts in storage cells of cereal grains, all of which have ingeniously developed from undifferentiated proplastids in the meristemic primordia. Plastids change their morphology dynamically in response to environmental conditions and developmental status. Related to these plastid dynamics, the quality and quantity controls of proteins are necessary. Therefore, proteases are important as key regulators in almost all processes during the conversion of plastid types and the maintenance of plastid homeostasis. Recent progress in this field has revealed that various proteases and peptidases act on plastids. Results of the studies indicate that the vast majority of plastid proteases are homologous to prokaryotic ones because plastids are thought to originate from endosymbiosis of ancestral cyanobacteria. Moreover, the diversification of subunits of several plastid proteases has been revealed along with new insights into the functions of these homologues. This review provides basic information related to plastid proteases and the current view of their physiological roles in plastid homeostasis and biogenesis.

12. Conclusion This project is has came to its conclusion, but through this we have learnt a lot of things which we were unaware of, like the whole role of Plastids. We have learnt many new role about Of Plastids in plants. We have also learnt about different types of Plastids and its role in Plant. Plastid is a generic name of divergent plant organelles, such as chloroplasts in green leaves, etioplasts in dark grown seedlings and amyloplasts in storage cells of cereal grains, all of which have ingeniously developed from undifferentiated proplastids in the meristemic primordia.

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