Genetics

cell organelles

1. PRESENTATION ON STRUCTURES & FUNCTIONS OF CELL ORGANELLES IN PLANT CELL Submitted to : Submitted by : Dr. N. K. Sharma Sanjay Kumar Sanadya Professor M.Sc. PBG previous

2. CELL ORGANELLES V arious membranous bound structures that are found within a cell are known as cell organelle. Cell organelles is studied with the help of electron microscope . Various cell organelles present in a plant cell as follow :- S.no Cell organelles S. No Cell organelles 1 Cell wall 8 Plastid 2 Plasma membrane 9 Vacuole 3 Nucleus 10 Ribosome 4 Endoplasmic Reticulum 11 Peroxisome 5 Golgi bodies 12 Cytoskeleton 6 Lysosome 13 Sphaerosome 7 Mitochondria

3. 1.CELL WALL Discovered by Robert hooke . Outermost part of the cell is always non-living is called cell wall. Parts of cell wall are :- Primary cell wall :- It is thin and elastic and lies between middle lamella. It is mainly consists of cellulose, hemicellulose. Secondary cell wall :- It is innermost layer of cell wall and lies between primary cell wall and plasma membrane. 3 . Middle lamella :- Common layer between adjacent cells. It is consists of calcium and magnesium pectate. It is developed during cell division i.e., cytokinesis

4. Cell wall Function:- To protect inner parts of cell. To give definite shape to the cell. To provide mechanical support to the tissues.

5. 2. PLASMA MEMBRANE Cytoplasm surrounded on the outer surface by a living, thin, selectively permeable and flexible boundary known as plasma membrane. The cell membrane possess carbohydrates, lipids and proteins. Carbohydrates present in the form of oligosaccharide of the glycolipids & glycoproteins. Lipids mainly phospholipids such as lecithin, cephalin , cholesterol etc. Two type of proteins are present in plasma membrane :- Integral protein (B) peripheral protein It’s thickness about 75-100 A ˚ and three layered protein-lipid-protein membranes. Bilayer of phospholipids are 35 A˚ thick layer, the protein layer are 20-25 A˚ thick layer. Lipids layer is hydrophobic and protein layer is hydrophilic type. Function :- Ingestion of material through endocytosis. Egestion of waste materials from cell through exocytosis. It checks the entry of toxic elements.

6. 3 .NUCLEUS First discovered by Robert brown in 1833 . It is also called controlling Centre of the cell. The nucleus may be different shape and size. Nuclear membrane It is double layer boundary of the nucleus which is about 200 A ˚ thick. 2 . Nucleolus A spherical body found in the nucleus. Granular region is 150-200 A ˚ in diameter contains proteins and RNA. 3. Chromatin It is partly culmed and tangled mass of nucleoprotein fibers in which consists DNA, proteins, RNA and other compounds complexes. Function :- Inheritance of characters. Protects chromosomes from cytoplasmic effects. Permits transports of material between cytoplasm and nucleus. Formation of ribosomes and synthesis of RNA.

7. 4. Endoplasmic Reticulum The presence of a network of reticulum of tiny tabular structures scattered in the cytoplasm. ER is attached to nuclear membrane on one side & plasma membrane on the other. ER have three components, viz., tubules, vesicles, cisternae. It is two type - R ough ER Presence of ribosomes on the membranes. 2 . Smooth ER Absence of ribosome on the membranes. Function :- Protein, lipid, glycogen synthesis. Acts as inter cellular transport system for various substances. Provides passage for mRNA from nucleus to the cytoplasm. Detoxification Precursor of secretory material to golgi bodies.

8. 5.Golgi bodies Also called golgi complex, dictyosome, Dalton complex, idiosome . Densely stained reticular structures near nucleus. Golgi body is made up of four parts - Cisternae - flat disc like shaped, sacs like structure many cisternae are arranged in a stack. 2. Tubules – branched & irregular tube like structure associated with cisternae. 3. Vacuoles – Large spherical structure associated to tubules. 4. Vesicles – Spherical structure arise from budding from tubules. function:- Cell secretion. Synthesis of cell wall. Formation of lysosome.

9. 6. Lysosome It is Membrane bound vesicular structures formed by the process of packaging in the golgy body. Presence of almost all type hydrolytic enzymes which is active at acidic pH (pH =5) viz., lipases, proteases, carbohydrases etc. In higher plants lysosome are less frequent. Function :- Intracellular digestion Extracellular digestion Autolysis (0.1 -0.8 μ m) membrane (single unit) lysosome Acid hydrolases pH=5 Nucleases Proteases Lipases Phospholipases Glycosidases

10. 7. Mitochondria Given by C. Benda Also called power house of cell. Mitochondrion membranes :- Double layer membrane Each membrane is 60-75 A˚ thick &separated by a space called perimitochondrial space. Cristae :- Inner membrane has a series of inside folds. It has F1 particles or oxysomes which is site of Electron Transport S ystem. Matrix :- Space between cristae into the inner chamber. It’s have DS circular DNA molecules, 70S ribosomes, amino acids, enzymes and others elements. Function :- Site of aerobic respiration. Semi autonomous organelles. Oxidation of carbohydrates, lipids & proteins. Cytoplasmic inheritance

11. 8. Plastid Discovered by Haeckel. It is found in all plants cells which is basis of presence of pigments can be classified into:- Chromoplast :- carotenoid pigments like carotene, xanthophyll & other are present. This gives yellow, orange or red colour to the part of the plants. 2. Leucoplast :- colourless plastids of various shapes and sizes with stored nutrients: Amyloplasts store carbohydrates. elaioplasts stores oils and fats. aleuroplasts stores proteins. Chloroplast:- also called kitchen of cell . it is contains chlorophyll and carotenoid pigments which are responsible for trapping of light energy. This gives green colour of part of the plant.

12. Chloroplast It is found in the mesophyll cells of leaves may be various shape and sizes. Parts of chloroplast:- Membranes : Double membrane bound layer separated by a space peri-chloroplastidial space. Stroma :- The Space limited by the inner membrane is called stroma. Component of stroma :- Thylakoids : A number of flatted membranous sacs are present called thylakoid which is arranged in stacks called grana. Each chloroplast contains 20-100 granum. 2 others: DS circular DNA, 70S Ribosomes, enzymes, other material are present in stroma. Function:- Site of photosynthesis. Cytoplasmic inheritance. Chloroplasts impart the pleasing greenary to the earth. chloroplast stores vitamin K, E RUBISCO protein and ions.

13. 9. Vacuole Single Unit Membrane bound space found in the cytoplasm. I t contains water, sap, excretory product & other materials. It membrane called tonoplast . in plant cell the vacuoles can occupy up to 90% of the volume of the cell. Function :- Transport of ions and other material against concentration gradients. To maintain high internal water pressure. Physical support of plant tissues. tonoplast cell sap Vacuole Water Sap Mineral matter Excretory product

14. 10. Ribosome D ensely stained granular structures in which is consists of RNA, proteins which are not surrounded by any membrane. It is smallest cell organelles also called protein factory of cell. I n lower prokaryotes , mitochondria and chloroplast present in 70S type & in eukaryotes present in 80 S type ribosome. In ribosome two sub unit are present: Large sub unit –binding site of t-RNA. Small sub unit – binding site of m-RNA. A-site :- accepter site for t-RNA. P-site :- site for growing polypeptide chain. Function :- Protein synthesis. Polysome :- at the time of protein synthesis, several ribosomes become attached to mRNA with the help of smaller sub unit.

15. 11. Peroxisome These are membrane bound vesicles that contains powerful oxidizing agents like hydrogen peroxide. Function :- photorespiration ( glycolate pathway):-In the plant cell, presence of light oxygen is used and carbon di oxide is formed like normal respiration. It is involved in β -oxidation of fatty acid. membrane peroxisome Oxidizing agents

16. 12. Cytoskeleton A network of protein fibers extending across and around the cell called cytoskeleton. In cytoskeleton consists of three classes of fibers: Microtubules : these tubules are 150-200 A ˚ in diameter ;which is made up of tubulin molecules arranged in series. It is associated with cell wall in plants Function : Transport cell wall material from golgy body to outside the cell. During cell division, formation of spindle fibers. 2. Actin filaments It is composed of contractile protein, Actin. Function:- to exert force to change cell shape internally .

17. 3. Intermediate filaments It is network of specific protein fibers like keratin, desmin , vimentin and neurofilament. Function :- They provide rigidity to cell shape .

18. 13 . Sphaerosome Sphaerosome are vesicles of 0.5-1 μ m diameter surrounded by a membrane, and contain up to 98% lipid. it is present in plant cell only, & contain some acid phosphatases enzyme. Function Major site of lipid synthesis and storage in plants. mambrane Sphaerosome Acid phosphatase Lipid synthesized enzyme

19. Key References:- Singh, B.D. 2013. Genetics. Kalyani Publishers , New Delhi Singh, P. 2009. Elements Of Genetics. Kalyani Publishers , New Delhi

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