Cellular Classification, Sub-cellular organelles

Cell is basic structural and functional unit of all living organism. Cell is enclosed in a compartment containing aqueous fluid called as Cytosol which is surrounded by a cell membrane called Plasma membrane

1. Cellular classification, Sub-cellular organelles Presented by MD ALTAMASH AHMAD PHARM D 3 RD YEAR

2. CELL - definition 2 Cell is basic structural and functional unit of all living organism Cell is enclosed in a compartment containing aqueous fluid called as Cytosol which is surrounded by a cell membrane called P lasma membrane Cell = Plasma membrane + cytoplasm Cytoplasm = Cytosol + Subcellular organelles

3. CELL – Classification (according to cellular structure) 3

4. Prokaryotes Unicellular organisms First life form on earth Lacks well defined nucleus and membrane bound organelles Simpler and smaller than eukaryotic cell The genetic material (DNA) consists of single chromosome and is present in the cytoplasm (no nucleus) E.g. – bacteria – Archaebacteria, eubacteria, cyanobacteria 4

5. 5 Figure. Prokaryotic Cell

6. Components of prokaryotic cell A prokaryotic cell has a jelly like cytosol within the cell in which other cellular components are found - They consist of – Cell membrane Cytoplasm Ribosomes Genetic material (RNA, DNA) Plasmids Cell wall Cell capsule or envelope Flagella Pilli or fimbriae 6

7. Eukaryotic cell Mostly multicellular Eukaryotic cells have the nucleus enclosed within the nuclear membrane . A cell wall is the outermost layer of the eukaryotic cells . The cells divide by a process called mitosis . The eukaryotic cells contain a cytoskeletal structure . The nucleus contains a single, linear DNA, which carries all the genetic information . 7

8. Figure. Eukaryotic Cell 8

9. Sub-cellular organelles of Eukaryotic cell A Eukaryotic cell contains- Plasma membrane Cytosol Subcellular organelles Sub-cellular organelles are bathed by cytosol and include – Nucleus, Mitochondria, Endoplasmic Reticulum, Ribosomes, Golgi Apparatus, Lysosomes, Peroxisomes And Cytoskeleton . All sub-cellular organelles, except ribosomes and cytoskeleton , are compartments within the cell, surrounded by their own membrane and contains aqueous fluid 9

10. Cell membrane (Plasma membrane) made up of lipid bilayer, thin hydrophobic sheet in fluid state which envelopes the cell lipid bilayer is made up of amphipathic lipid molecules (having both hydrophilic or polar part and a hydrophobic or non-polar part) Also known as plasma membrane Function – Provides external boundary for cell and its organelles Maintain the shape, size and integrity of cell and its organelles Flexibility of cell membrane allows in shape changes as growth occurs Membrane mediates cell-to-cell communication between adjacent cells by gap-junctions 10

11. 11 Figure. Cell membrane

12. Cell membrane – function (contd..) 12 Membrane regulates the flow of information between cell and its environment Cell membrane also helps in exocytosis and endocytosis Selectively permeable to molecules - as lipid bilayer is hydrophobic so it is permeable only to lipid soluble substances and impermeable to hydrophilic/polar substances - membranes also have transport systems, to facilitate the transport of polar substances across the cell Membranes regulate the transport of substances like nutrients , ions, gases, water, various products , wastes into and out of cells and their organelles

13. 1 . Nucleus largest sub-cellular organelle double membrane – nuclear membrane, surrounds it. The outer and inner membranes are separated by lumen. The outer membrane of the nuclear envelope is continuous with the endoplasmic reticulum (ER) membrane At intervals nuclear membrane has nuclear pores, permit the passage of molecules in and out of the nucleus. nucleus of eukaryotic cell contains a dense body known as Nucleolus rich in rRNA. Nucleoplasm – ground material of nucleus rich in enzymes such as, DNA polymerases, RNA polymerases, etc. 13

14. 14 Figure. Nucleus

15. Nucleus - functions By DNA replication provides genetic information to offspring or daughter cells during cell division., thus it is blue print of life. By transcription (RNA synthesis) provides information for the synthesis of all protein molecules of the cell. Both replication and transcription take place in the nucleus . 15

16. 2. Mitochondria – powerhouse of the cell spherical, oval or rod like bodies. have two membranes – outer and inner membrane. outer membrane is smooth which has a large number of special proteins known as the P orins, while the inner membrane is for folded to form cristae The central cavity of the mitochondrion contains the matrix Matrix contains enzymes and chemical intermediates of -- TCA cycle Heme synthesis Urea cycle, etc. Also present in the matrix are, mitochondrial DNA , RNA and ribosomes. 16

17. 17 Figure. Mitochondria

18. Mitochondria - functions ETC and oxidative phosphorylation components -- situated in inner mitochondrial membrane are involved in ATP synthesis , hence mitochondria are regarded as ‘powerhouse of the cell’ Some of the major pathways operate in the mitochondria . They are, TCA cycle, -Oxidation of fatty acid, ketone bodies formation , gluconeogenesis (partly), urea cycle (partly ), heme synthesis (partly), pyrimidine synthesis (partly ). Mitochondrial DNA codes for some of the mitochondrial proteins involved in oxidative phosphorylation 18

19. 3. Endoplasmic Reticulum (ER ) network of membrane-enclosed spaces extends throughout the cytoplasm. classified into - R ough and S mooth ER 1. rough appearance (when observed under electron microscope) is due to ribosomes attached to the cytoplasmic side of the membrane. 2. smooth ER does not have ribosomes. Functions- Rough ER : involved in synthesis of proteins (lipoproteins , glycoproteins ) 19

20. 20 Figure. Endoplasmic reticulum

21. Functions (contd.. ) 21 • Smooth ER: I. Metabolism of drugs and toxic compounds ( CYP450 monooxygenases are present in liver cell smooth ER) II. Synthesis of lipids (TAG, phospholipids, cholesterol ) III. Ca2+ storage in skeletal and cardiac muscle .(note- sarcoplasmic reticulum of muscle is a modified ER)

22. 4. Golgi apparatus (Golgi complex) group of membrane bound flattened tubes or sacs placed one over another in a pile or stack. Functions- Main functions of Golgi apparatus are protein sorting, packaging and secretion . newly synthesized proteins are handed over to the Golgi apparatus, which catalyze the addition of carbohydrates , lipids or sulfate moieties to the proteins. 22

23. 23 Figure. Golgi apparatus

24. 5. Lysosomes (suicidal bags of cell) membrane bound vesicle containing various hydrolytic enzymes ( hydrolases) Lysosomal enzymes are capable of digesting proteins , carbohydrates, lipids and nucleic acids in case of attack on cell by foreign substance like any pathogen pH inside the lysosomes is less than that of cytosol necessary for its digestive function 24

25. 25 Figure. Lysosome

26. Lysosomes - functions hydrolases enzyme breakdown the complex molecules brought into the cell by endocytosis , phagocytosis or worn-out organelles from the cells own cytoplasm. Lysosomes - termed as ‘suicide-bags ’ as their lysis can lead to digestion and death of the cell 26

27. 6. Peroxisomes small spherical or oval membranous bodies It contain enzymes peroxidases and catalase Functions Catalase and peroxidase enzymes destroys unwanted peroxides and other free radicals as free radicals are capable of damaging cell membranes, tissues, and genes. These free radicals are also responsible for inflammatory diseases , ageing process and malignant transformation . 27

28. 28 Figure. Peroxisome

29. 7. Ribosomes These are Nucleoproteins present either freely in cytosol or bound to Endoplasmic reticulum Function provide necessary infrastructure for mRNA , tRNA & amino acid to interact with each other for translation process 29 8. Cytoskeleton Made up of microtubules and actin filaments role in maintaining the cellular structure, mobility and cell division.

30. 30 Figure. Ribosomes

31. Summary Name Definition 1. Cell Basic structural and functional unit of living organism 2. Prokaryotes First and oldest, unicellular life form, without membrane bound nucleus and other organelles 3. Eukaryotes Unicellular or multicellular, complex cellular organisms, having membrane bound organelles and well defined nucleus 4. Cell membrane (plasma membrane ) Lipid bilayer, gives shape, size and maintain integrity of cell and its organelles 31

32. Summary Organelle Function 5. Nucleus Provides genetic information to offspring RNA transcription, directs protein synthesis 6. Mitochondria Energy production from the oxidation of food substances and the release of adenosine triphosphate 7. Endoplasmic reticulum Translation and folding of new proteins (rough endoplasmic reticulum), synthesis of lipids (smooth endoplasmic reticulum) 8. Golgi apparatus Sorting, packaging, and modification of proteins 32

33. Summary (contd..) Organelle function 9. Lysosome Breakdown of large molecules, acts as cell’s own suicidal bag 10. Peroxisome breakdown of metabolic hydrogen peroxide and free radicals 11. Ribosome Translation of RNA to form proteins 12. Cytoskeleton Maintaining the cellular , shape, motility and cell division. 33

34. 34 Thank You