Cell biology

Cell biology ppt

1. Cell Biology Presented by Rajwanti Saran Ph. D. (Ag.) PBG RARI, Durgapura , Jaipu r

2. Matter of Concern ……….. 1. Introduction 2. History of cell 3. Cell theory 4. Cell organelles

3. Introduction Cell biology : Branch of biological science which deals with the study of structure, function, molecular organization, growth, reproduction and genetics of the cells. Cell biology mainly concern with study of structure of cell and function of specialized cells.

4. History The term cell - Robert Hooke (1635-1703) in the mid seventeenth century to describe the structure of cork. Anton van Leeuwenhoek (1632-1723) - first recorded observations of bacterial cells (termed "animalcules") from pond water & tooth scrapings. 1830s –importance of cells realized 1838 - German botanist Matthias Schleiden (1804-1881) observed that despite differences in tissue structure, all plants tissues were made of cells.

5. CONT…. 1839 - German zoologist Theodor Schwann (1810-1882) realized animals were also composed of fundamental cellular units or cells. Schwann proposed first 2 principles of Cell Theory: a) All organisms consist of 1 or more cells b) The cell is the structural unit of life Schleiden -Schwann view of cell origin was less insightful – i.e. cells could arise from non-cellular materials German physician Rudolf Virchow (1821-1902) demonstrated that living cells could arise only from other living cells (biogenesis), and not from inanimate matter ( abiogenesis ).

6. CELL Cell is the basic structural and functional unit of cellular organisms, except viruses. Cell is a Latin word , that means “small room” A.G. Loewy and P. Siekevitz (1963) have defined a cell as “ a unit of biological activity delimited by a semi-permeable membrane and capable of self-reproduction in a medium free of other living systems”.

7. Properties of a Cell Cells are - Highly complex and organized Possess a genetic program and the means to use it Capable of producing more of themselves Acquire and utilize energy Carry out a variety of chemical reactions Engage in mechanical activities Able to respond to stimuli Capable of self-regulation

8. TYPES OF CELL

9. Differences b/w prokaryotic cell and eukaryotic cell Prokaryote Cell Eukaryote Cell 1. Size – small 1- 10 μm 2. Unicellular 3. Has single membrane and cell wall 4. No nucleus. 5. Circular DNA 6. No Histones . 7. No cell organelles 8. Ribosomes – free in cytoplasm. 50S +30S {70S} 9. Cell division – by fission 10. Cytoskeleton – absent has flagella Ex- bacteria,rickettsia 1.Large - 10 - 100 μ m 2. Multicellular 3. Membrane bilayer . 4. Nucleus –well defined. 5. Linear DNA. 6. Histones 7. Membrane bound Organelles. 8. Ribosomes – on surface of E.R. 60S +40S {80S} 9. By mitosis. 10. Present. Ex- fungi,plants,animals

10. Prokaryotic cell

11. Eukaryotic cell ANIMAL CELL PLANT CELL

12. Animal cell v/s plant cell

13. Components of a cell A cell is composed of hyloplasm and various structures or cell organelles like cell wall, cell membrane / plasma lemma, endoplasmic reticulum, ribosomes , golgi bodies, lysosomes , spherosomes , chloroplasts, mitochondria, centriole and nucleus.

14. Cell organelles Organelle (“little organ”)= a small structure in the cell that performs a specific function. Membrane-bound organelles are found only in eukaryotic cells.

15. Cytoplasm Everything in a cell except the nucleus is cytoplasm. Clear, gelatin-like, watery substance surrounding the organelles. Composition: 1) Water = 90% 2)Organic and inorganic compounds = 10%

16. Functions of cytoplasm Maintains the shape and consistency of the cell. Allows for chemical reactions necessary in metabolism. Site for many metabolic pathways. Ex- Glycolysis , Protein synthesis , fatty acid synthesis, purine synthesis.

17. Cell wall Plant cells are surrounded by a nonliving and rigid coat called cell wall.

18. The cell wall of a differentiated cell has the following 3 parts: a) Middle lamella: The walls of contiguous cells are joined by middle lamella. It is composed of calcium and magnesium pectate . b) Primary cell wall : It is lies b/w ML and secondary cell wall/plasma lemma. It is composed of hemicellulose (53%), cellulose (30%), pectin (5%), protein (5%) and lipid (7%). c) Secondary cell wall: Inner most layer of wall. It is composed mainly of cellulose but it also contains lignin, suberin and cutin .

19. Functions of cell wall Provide plants to a definite shape, mechanical support and strength to tissues and organs.

20. Plasma lemma Boundary of the cell. Made of a phospholipid bilayer , with protein molecules scattered all over. Composition : Protein = 40% and lipid = 60% Functions: 1. Regulate the movement of various molecules into and out of the cytoplasm. 2. It forms a protective barrier b/w the intracellular and extracellular environments.

21. Structure of plasma lemma

22. Mitochondria Mitochondria was first seen by kollicker in 1850 in muscles and called them ‘ sarcosomes ’ Altmann (1890) observed these structures and named them ‘ bioblasts ’. Benda (1898)stained these organelles with crystal violet and renamed them ‘mitochondria’

23. Structure Mitochondria have a double membrane structure. 1) Outer membrane: Contain large number of integral protein called porins (Allow material in and out of the mitochondria). Enclosed the entire organelle. 2) Inter membrane space/ Peri -mitochondrial space: ions and sugars in the intermembrane space is the same as the cytosol .

24. Cont… 3) Inner Membrane: It is folded double phospholipid layer . Site for the production of ATP. Specific transport of protein that regulate metabolite passage in and out of the matrix. 4) Cristae and Matrix: Cristae is the folding of the inner membrane that allows more surface area, enhancing its ability to produce ATP. The matrix is the space enclosed by the inner membrane.

25. Chemical Composition Protein = 70% Lipid = 25-30% RNA = 1% DNA < 1%

26. Function Important and main function is to produce ATP. Therefore it is called the power house of the cell (ETS). Krebs cycle of cellular respiration is takes place in mitochondrial matrix. Regulate cellular metabolism. Play important role in cytoplasmic inheritance. Eg . CMS Site of metabolic pathways.- TCA cycle, Urea Cycle, F.A Oxidation etc.

27. Structure

28. Chloroplast Found only in plant cells and plant-like protists It contains Chlorophyll, hence it imparts the characteristic green colour to plants and carry out photosynthesis, the ultimate source of all organic compounds. Average cell may have 20-40 chloroplast. Chlamydomonas have 1chloroplast \ cell

29. Chemical Composition Protein = 50-59% Lipid = 21-34% Chlorophyll = 5-8% Carotenoids = 0.7-1.1% RNA = 1-7.5% DNA = 0.2-1%

30. Origin And Evolution

31. Structure Planoconvex lens- like structures (5μm x 2-3 μm ) Double layered envelope Granular stroma or matrix Lamellar system Osmophilic globules ( Plastoglobuli ) Chloroplast DNA

32. Function Main function is photosynthesis. Contribute to heredity in the form of cytoplasmic inheritance.

33. Energy Transduction

34. Photosynthetic complexes distributed in thylakoid membrane

35. Maternal inheritance of chloroplast genome Nuclear genomes higher eukaryotic organisms are diploid and shows sexual reproduction. Gametes result from meiosis are haploid Fertilized zygote inherits one nuclear allele of each gene from each parent But cytoplasmic organelles contain multiple, homogeneous genomes inherited from female parent ( cytoplasmic inheritance). In tobacco and many other plants, mitochondrial and chloroplast genomes are specifically degraded (in male gamete) before fertilization. There are many exceptions

36. Alleles A, B and C from the female parent and a, b and c from the male parent

37. Chloroplast DNA based cytoplasmic inheritance of leaf color in Four O’clock (Mirabilis ) plant

38. Endoplasmic reticulum A web-like series of membranes within the cytoplasm in the form of flattened sheets, sacs, tubes, creates many membrane enclosed spaces - spreads throughout the cytoplasm - has connections with the outer membrane of the nucleus and the plasma membrane. “E.R.” ( endo means inside + cyto plasmic + reticulum means network = network of membranes inside the cytoplasm) Interconnected network of tubules and vesicles – cisternae .

39. Structure

40. Two types of ER Rough ER - studded with ribosomes Site of synthesis of many proteins All ribosomes on rER are actively involved in protein synthesis - Smooth ER - site for synthesis of steroids and other lipids, Ca++ storage in muscles Detoxification of drugs, toxins, alcohol (especially in liver )

41. Function RER- synthesizes proteins. SER- synthesizes phospholipids, cholesterol (in many tissue) & steroid hormones (adrenals, gonads). SER - site of Glycogen metabolism. Removes the phosphate group from G-6-P; and release free glucose in blood. In liver & Kidney - Detoxifies drugs, toxins & Carcinogens. Circulation and transport Storage of proteins and minerals A large surface area for enzyme action.

42. Golgi complex Consists of 3 to 20 cisternae , small, flattened membranous sacs. Prominent in cells that secrete proteins Accept vesicles on one side and produce vesicles on the other

43. Structure

44. Function Modification of proteins and lipids Storage and packaging of molecules POST OFFICE OF CELL

45. Ribosome Protein synthetic machinery Two subunits - large and small - each made of protein and ribosomal RNA ( rRNA ) Granular structures present on surface of ER & also as free 1st observed by George Palade (1953) Non membrane bound organelle Measure ~ 22 x 32 nm. Contain 85% RNA of cell

46. Functions Subunits associate when they are synthesizing proteins Protein synthesis occurs on ribosomes that are free-floating in the cytoplasm and on ribosomes attached to ER rRNA is synthesized in the nucleolus

47. Structure

48. Lysosome Vesicles filled with digestive enzymes - used for intracellular digestion. Particles can be taken into cell by phagocytosis and vesicle fused with lysosome . The components of organelles can be recycled after digestion by lysosomes . Functions: Garbage disposal. Breakdown bacteria entering cell, worn out organelles, intracellular digestion.

49. Function

50. Vacuole Membrane bound sac Contains liquids or solids Larger than vesicles

51. Function Storage container for water, food, enzymes, wastes, pigments, etc.

52. Centriole part of specialized region of the cell called the centrosome (cell center) found in animals and most protists the centrioles are involved in the production of microtubules microtubules have many functions including moving chromosomes during cell division centriole structure - 9 triplets of microtubules surrounding a hollow core . similar to the basal body of flagella

53. Structure Centrioles are short cylinders, arranged at right angles to each other.

54. Cytoskeleton A network of protein filaments that extends throughout the cytoplasm. Anchored to plasma membrane. Dynamic structure. Three types of filamentous proteins - Microtubules Intermediate filaments Microfilaments

55. Microtubules Long, Hollow, unbranched , polar cylinders, made up of protein “ tubulin ”(α & β tubulin ), The largest of cytoskeletal components. Major components of axons and dendrites. Functions:- Microtubules help in structural support and maintain the shape of the cell. Helps in movement of organelles,secretory vesicles and exocytosis . Formation and function of mitotic spindle. Movement of cilia and flagella.

56. Intermediate filaments Polymers of long rod like proteins. These filaments are thicker than microfilaments but thinner than microtubules. Made up of – Keratin,desmin,neurofilaments etc. Functions :- Provide mechanical support to the cell. Helps in intercellular attachment. Provide strength and rigidty to neurons. Major structural role in skin and hair cells.

57. Microfilaments Thinnest elements of the cytoskeleton. Composed of the protein actin , (β , γ actin ) Form a meshwork under plasma membrane Stress fibres . Functions :- Mechanical support for the basic strength & shapes of cells. ex- Microvilli is rich in microfilaments – Shape. Involved in muscle contraction, cell division, and cell locomotion.

58. Structure .

59. Function Provides shape to cell. Acts as internal framework. Helps in uptake of materials into cell. Helps in internal movement of cell organelles , movement of cells and muscle contraction. Helps in Cell division.

60. Peroxisome Also known as microbodies “ Subcellular respiratory organelles” 0.5 μ m in diameter Predominantly present in Hepatocytes & Tubular Epithelial cells. Surrounded by a membrane. Contain several oxidases . – Peroxidase , Catalase . Create H2O2 as a byproduct and degrade it with the enzyme catalase .

61. Functions Oxidation of amino acids. Oxidation of long chain fatty acids. Protects cell from the toxic effects of H2O2. Used for removing reactive compounds from the cytoplasm Essentially contain two types of Enzymes Oxidases : which are active in oxidation of lipid Catalase : which act on Hydrogen Peroxide to liberate Oxygen.

62. Spherosome Vesicles of 0.5-1 micron diameter, surrounded by a membrane. Found only in plant cells. Composition: 98% lipid + some acid phosphates Function: - Lipid storage

63. Nucleus Control center of the cell – has the information needed to oversee the chemical reactions in cells. Prominent & Characteristic features ‘ Eukaryon ’ means ‘true nucleus’ Very essence of eukaryote – membrane bounded nucleus

64. Functions Stores genetic information Controls cell division Directs functioning of cell (provides template for RNA -protein synthesis) Physically separates DNA from the cytoplasm’s complex metabolic machinery Nuclear membrane serve as boundary

65. Components of Nucleus 1. Nuclear Envelope – pore riddled 2. Nucleoplasm – Fluid interior portion 3. Nucleolus – Dense cluster of RNA & Proteins – ribosomes 4. Chromatin – all DNA + Proteins

66. The Nuclear Envelope Inner and outer nuclear membrane with perinuclear space 7-8 nm thick and trilamellar appearance Inner membrane lined with fiber network – Nuclear lamina- 10 to 40 nm Nuclear lamina – intermediate filament (protein) called as Lamins Nuclear lamina – support to NE & attachment sites for chromatin.

67. Cont… Outer membrane - continuous with ER Outer membrane studded with ribosomes – protein synthesis. Perinuclear space – 20 to 40 nm continuous with cisternae of ER E/M - filaments of cytoskeleton extend outward cytoplasm – anchored to organells / plasma membrane – known as Nuclear matrix Matrix - shape of nucleus

68. The Nuclear Pore Most distinctive feature of NE Small cylindrical channels –direct contact b/w cytosol & Nucleoplasm Readily visible – freeze fracture microscopy Density - cell type & activity

69. The Nucleolus Ribosome factory large, prominent structures Doesn’t have membrane E/M it consists; 1. Fibrillar component - DNA (unraveled chromatin loops) + RNA component of ribosome - DNA carries genes for rRNA - NOR - RNA is r RNA – synthesized & processed - dense areas, transcription going on

70. Cont … 2. Granular component - rRNA molecules + Proteins - forms ribosomal subunits – exported to cytoplasm Size correlated with level of activity Cells having high rate of protein synthesis –many ribosomes –20 to 25% of nucleus Main difference – granular component present

71. Cont… During cell division – condensation of chromatin into compact chromosomes Shrinkage and disappearance of nuclei rRNA & protein disperse/ degraded After mitosis – chromatin uncoils, NOR loop out, rRNA synthesis resumes Many tiny nucleoli visible – fuse & become large nucleolus

72. Chromatin/ Molecular structure of chromosomes Eukaryotic chromosomes – two broad components. 1.Nucleic acids: - DNA (primary nucleic acid) + small amt of RNA (transit to the cytoplasm) 2. Proteins: i. Histones (basic pH) – core histones (H2A, H2B, H3 & H4), Linker histone (H1) ii. Non- histone proteins

73. Cont… Histones bind to – vely charged DNA – stability to the DNA Mixture of DNA & proteins – basic structural unit of chromosomes - chromatin fiber E/M examination of intephase chromatin – ellipsoidal beads joined by linker DNA known as Nucleosomes .

74. Nucleosome Simplest packing str of DNA 146 bp DNA wrapped around histone octamer Octamer = 2 copies of 4 core histones DNA length varies b/w species Core DNA – DNA associated with histone octamer Linker DNA – DNA b/w histone octamer – 8 to 114 bp

75. Cont.. Model of packing of chromatin and the chromosome scaffold in metaphase chromosome

76. Chromatin Chromatin can be differentiated into two regions (during interphase & early prophase) 1.Euchromatin – lightly staining 2.Heterochromatin – densely staining

77. Types of chromatin EUCHROMATIN 1. Lightly staining regions 2. Less tightly packed chromatin fibers therefore non condensed 3. Not visible – light microscope, undergo regular changes in morphology with cell division 4. Genetically active regions 5. Replicates earlier during S phase 6. GC rich HETEROCHROMATIN 1. Darkly staining 2. Tightly packed chromatin fibers therefore condensed 3. Visible, remain highly condensed in all stages 4. Genetically inactive regions – either they lack genes/ contain genes that are not expressed 5. Replicates later during S phase 6. AT rich

78. Organelles – “factory components with function” Support - Cell wall , cell membrane cytoskeleton, microtubles Controls material entering and leaving - Cell membrane, pores Internal transport system – Endoplasmic reticulum Powerhouse - mitochondria Control center – nucleus, organelle DNA for mitochondria and chloroplast Production of key products – ribosomes , endoplastic reticulum, chloroplasts Packaging center for shipment of products – Golgi Apparatus, ER Shipment of materials out of cell - Golgi Apparatus, vesicles Storage of liquids and solids – Vacuole, vesicles, plastids, Recycling center – Lysosomes and perixosomes Convert light energy to chemical energy - chloroplasts Allows new cell factories to be produced – nuclear DNA, centrioles , cell wall