Cell: The Unit of Life PDF

CELL : THE UNIT OF LIFE By:-Raushan Kumar Singh  CELL : THE UNIT OF LIFE What is Cell ? Cell is the structural and functional unit of an organism. Uni...

CELL : THE UNIT OF LIFE By:-Raushan Kumar Singh  CELL : THE UNIT OF LIFE What is Cell ? Cell is the structural and functional unit of an organism. Unicellular organism All organisms are composed of cells. Some are composed of a single cell and are called unicellular organisms. While others composed of many cells, are called multicellular organisms. Multicellular organism  CELL : THE UNIT OF LIFE Minimum Requirement in a Cell Cell Membrane Cytoplasm Complete cell (show independent existence) Genetic material  Unicellular organisms are capable of :- Independent existence. Performing the essential functions of life. Unicellular organism  CELL : THE UNIT OF LIFE  Anything less than a complete structure of a cell does not ensure independent living.  Ex:- Virus is not a complete independent living as it does not have own cytoplasm. Bacteriophage (Virus) History of cell  First cell discovered by :- Robert Hooke in Cork cells (Dead cell)  First living cell discovered by :- Anton Von Leeuwenhoek (living cell)  Nucleus discovered by :- Robert Brown  CELL : THE UNIT OF LIFE Cell Theory  Given by Schleiden and Schwann.  Matthias Schleiden (1838) :- Botanist, Examined a large number of plants and observed that all plants are composed of different kinds of cells which form cell the tissues of the plant. Tissue  CELL : THE UNIT OF LIFE  Theodore Schwann (1839) :- Animal Plant Zoologist , cell cell Studied different types of animal cells and reported that animal cells had a thin outer layer which is today known as the plasma membrane He also concluded, based on his studies on plant tissues that presence of cell wall is a unique character of the CELL CELL plant cells. On the basis of this, Schwann proposed the hypothesis that the bodies of animals and plants are composed of Thin outer layer cell wall cells and products of cells. (Plasma membrane)  CELL : THE UNIT OF LIFE  Schleiden and Schwann together formulated the cell theory :-  All living organisms are composed of cells and products of cells.  DRAWBACK :- This theory did not explain as to how new cells were formed. Rudolf Virchow (1855) :- Modern Cell Theory First explained that cells divided and new cells are formed from pre-existing cells (Omnis cellula -e cellula). He modified the hypothesis of Schleiden and Schwann to give the cell theory a final shape.  CELL : THE UNIT OF LIFE Cell theory as understood today is :- New cell  All living organisms are composed of cells and products of cells.  All cells arise from pre-existing cells. Cell Division Cell Size of cell (Pre - existing) New cell Smallest cell :- Mycoplasma (0.3 μm) in length PPLO :- about (0.1 μm) in diameter Typical Bacterial cell :- 1-2 μm Viruses :- 0.02 – 0.2 μm (but not a cell)  विचार करने योग्य बातें :- How First cell exist on earth - Human RBC :- 7 μm (approx) de-novo (अपने आप) means self Longest cell :- Nerve cell originated By interactions of biomolecules Largest isolated single cell :- Egg of Ostrich CELL : THE UNIT OF LIFE  CELL : THE UNIT OF LIFE Shape of cell Red blood cells White blood cells Columnar epithelial cells (round and biconcave) (amoeboid) (long and narrow) Mesophyll cells (round and oval) A Tracheid (elongated)  The shape of the cell may vary with the function they perform. Nerve cell  They may be disc-like, polygonal, columnar, cuboid, thread like, (Branched and long) or even irregular.  All eukaryotic cells are not identical.  CELL : THE UNIT OF LIFE Types of cell Prokaryotic cell Eukaryotic cell Well developed nucleus Absent Well developed nucleus Present  CELL : THE UNIT OF LIFE Parameter Prokaryotic Cells Eukaryotic Cells Membrane-bound Absent Present organelles Well-defined nucleus absent. Nucleus Well-defined nucleus present. nucleoid The cell size is larger(10-100 μm) in Cell size The cell size is smaller(0.1-5 μm) contrast Most eukaryotic cells are multicellular. Cell structure Unicellular structure However, some are unicellular More complex in comparison to Complexity Simpler prokaryotic cells The cell wall is present. Present Cell wall it comprises of mucopeptide or peptidoglycan Mitochondria Absent Present Ribosome 70S 80S Shape & Form Double-stranded circular DNA Double-stranded Linear DNA of DNA  CELL : THE UNIT OF LIFE Parameter Prokaryotic Cells Eukaryotic Cells Golgi Apparatus Absent Present Sexual reproduction is certainly the most Mode of Reproduction Asexual common here Binary fission, transduction, conjugation, Cell Division Mitosis and transformation Translation happens in the cytosol. Translation and It occurs together Moreover, transcription happens in the Transcription nucleus Number of chromosomes Only one More than one These cells have a single origin of These cells have multiple origins of Replication replication replication Organelles Membrane-bound organelles are absent Membrane-bound organelles are present Examples Archea and bacteria Fungi, protists, animals, and plants  CELL : THE UNIT OF LIFE AN OVERVIEW OF EUKARYOTIC CELL Cell wall Cell Boundaries Controller of the cell Cytoplasm = Cytosol (Liquid part) + Periplasmic space Trophoplasm (Solid part)  CELL : THE UNIT OF LIFE Cytoplasm (Main arena of cellular activities) Cytosol Trophoplasm Cytosol is mainly made of liquid or H2O Trophoplasm is mainly made of Solid part Cell organelle Deutoplasm (Living structure) (Non-Living structure) Like Like Golgi body Stored food etc. ER Ribosome Vacuole Mitochondria Chloroplast etc.  CELL : THE UNIT OF LIFE 1. Cell Wall Cell wall is non-living Rigid structure Permeable Cell wall present in :- Plants Algae Fungi Bacteria Animal  Cellulose  Cellulose  Chitin  Peptidoglycan  Hemicellulose  Galactans,  Polysaccharides Mycoplasma  Pectins  Mannans  Proteins.  Minerals like calcium carbonate.  CELL : THE UNIT OF LIFE Types of cell wall Middle lamella Cell Cell Middle lamella It is cementing common layer between two cells (so also called as Plant cement). Middle lamella consists of Ca & Mg pectate. (Amount of Ca is more.)  CELL : THE UNIT OF LIFE Types of cell wall Primary Cell wall Secondary Cell wall Thin Thick Elastic Rigid Qn. If composition of both primary and secondary cell wall is same then Capable of growth Unable to grow why one is elastic and thin whereas (due to elastic nature) one is rigid and thick ? Composed of Cellulose, Composed of Cellulose, Ans.- In primary cell wall, Cellulose, Hemicellulose, Hemicellulose, hemicellulose, pectin and proteins Pectin and Pectin and are loosely arranged, so they Proteins Proteins becomes elastic whereas in sec. cell wall, cell wall component is Gradually diminishes as Secondary cell wall compactly arranged, so they cell matures. absent in meristem. becomes rigid.  CELL : THE UNIT OF LIFE Tertiary Cell wall Tertiary Cell wall :- Primary cell wall Thin Present only in Tracheids of Gymnosperm. Composed of :- Hemicellulose, Xylan Secondary cell wall Cytoplasm Tertiary Cell wall Cell membrane  CELL : THE UNIT OF LIFE Formation of Cell wall materials  Plant cell wall is Composed of :- 1. Cellulose Formed in Cell membrane 2. Hemicellulose Formed in Golgi body (Dictyosome) 3. Pectins [Golgi bodies of plant cell is called Dictyosome.] 4. Proteins Formed on Ribosomes  CELL : THE UNIT OF LIFE Formation of Cell wall materials Formation of Cell wall materials Skeleton Matrix Formed by Formed by Cellulose Hemicellulose, Pectins, Proteins Cellulose ka chain Microfibrils or cellulose fibre banata hai  CELL : THE UNIT OF LIFE Plasmodesmata Cytoplasm Cytoplasm ER Nucleus DESMOTUBULES (Tubules of SER) Pore  CELL : THE UNIT OF LIFE Plasmodesmata Plasmodesmata name proposed by Strasburger. Plasmodesmata are cytoplasmic connections between two adjacent plant cells. Plasmodesmata are characteristic of multi-cellular plants. E.R. tubules (Desmotubules) help to maintain continuity of cytoplasm. Functions of Cell wall Cell wall gives shape to the cell. It protects the cell from mechanical damage and infection. It also helps in cell-to-cell interaction. It provides barrier to undesirable macromolecules.  CELL : THE UNIT OF LIFE 2. Cell Membrane Cell Membrane is also called as Plasma Membrane / Bio Membrane Thin Living Quasi-fluid (semisolid like honey or gel) Hence provide fluidity Selectively permeable (if in option not given then Semi-Permeable) Present in both prokaryotic and eukaryotic cell.  Average composition of Cell Membrane :-  Proteins - 58-59%  Lipids - 40% (Phospholipid, Cholesterol, Glycolipid)  Carbohydrate - 1-2%  CELL : THE UNIT OF LIFE  Chemical composition of Human RBC Membrane :-  Proteins - 52%  Lipids - 40% (Phospholipid, Cholesterol, Glycolipid)  Carbohydrate - 8%  The ratio of protein and lipids varies considerably in different cell types. Phospholipid Head Hydrophilic Polar Amphipathic molecule Hydrophobic Tail Non-polar Fatty acid Saturated fatty acid Unsaturated fatty acid (Solid) (Liquid)  CELL : THE UNIT OF LIFE H2O H2O Hydrophilic Head outside Hydrophobic Tail inside H2O Cytoplasm Head outside H2O Single layer of Cytoplasm Phospholipids Tail inside to protect from aqueous environment Bilayer of Phospholipids  CELL : THE UNIT OF LIFE Mature RBC Mature RBC does not have Nucleus, ER, Mitochondria Normal cell The detailed structure of the membrane was studied only after the advent (discovery) of the electron microscope in the 1950s. Chemical studies on human red blood cells (RBCs), membrane, enabled the scientists to deduce the possible structure of plasma membrane.  CELL : THE UNIT OF LIFE Structure of Cell Membrane Fluid Mosaic Model Carbohydrate Fluid mosaic model :- Given By Singer & Cholesterol Nicolson (1972) Latest & most widely accepted model for the structure of plasma membrane According to this model proteins are arranged in phospholipid as mosaic pattern. So membrane is termed as ‘’Protein iceberg in a sea of phospholipid.‘’ or ‘’ Gulab jamun Protein Phospholipid (protein ) in a concentrated solution (phospholipid) of sugar’’  CELL : THE UNIT OF LIFE 1. Lipids :- A. Phospholipids :- Phospholipid is the main component of cell membrane Forms continuous structural frame of cell membrane. Provide Fluidity :-  Due to unsaturated fatty acid. Phospholipid  CELL : THE UNIT OF LIFE B. Cholesterol :- More rigid than phospholipid. Provide stability of cell membrane. Present only in membrane of eukaryotic cells. In prokaryotic membrane, stability is provided by Hopanoids. Phospholipid :- Fluidity Quasi-fluid Cholesterol Cholesterol :- Stability The Quasi fluid nature of lipid enable lateral movement of protein within the overall bilayer. This ability to move within the membrane is measured as its, fluidity.  CELL : THE UNIT OF LIFE  Significance of fluidity :- 1. Cell growth :- Cell size increase 2. Cell division :- (Furrow formation)  CELL : THE UNIT OF LIFE 3. Endocytosis :- Ingestion of waste materials by cell through plasma membrane.  Types of Endocytosis :- I. Pinocytosis or Cell Drinking: - Ingestion of liquid material by plasma membrane in the form of vesicles or bag like structure (Pinosome) is called pinocytosis. II. Phagocytosis or Cell eating: - Ingestion of solid complex materials by plasma membrane in the form of vesicles (Phagosome) is called Phagocytosis.  CELL : THE UNIT OF LIFE 4. Exocytosis / Secretion / Emiocytosis /Cell vomiting :- Egestion of waste materials from cell through plasma membrane. 5. Formation of intercellular junction :-  CELL : THE UNIT OF LIFE 2. Protein :- On the of ease of extraction,membrane protein are of two types :- i. Extrinsic or Peripheral protein :- These are superficially arranged on the surface of lipid layer. It can be separate easily. These protein have enzymatic activity. Extrinsic or Peripheral protein  CELL : THE UNIT OF LIFE 2. Protein :- ii. Intrinsic or Integral protein :- These protein are tightly binds with phospholipid. Thus, they can not easily removed from membrane.  Intrinsic or Integral proteins are of 2 types :- a. Fully or Completely buried :- Totally buried through the complete thickness of membrane. Intrinsic or Integral protein Ex:- Tunnel (channel ) protein and carrier protein  CELL : THE UNIT OF LIFE 2. Protein :- b. Partially buried :- Incompletely buried through the thickness of membrane. Tunnel protein Carrier protein  CELL : THE UNIT OF LIFE 3. Carbohydrate / Sugar (Oligosaccharides) :- Sugar (Glyco) Sugar (Glyco) Function :- Protein Cell to cell recognition. Lipid Example :-  Fertilization (where sperm & egg recognize each other)  “Blood group Antigens”  CELL : THE UNIT OF LIFE  Flip - Flop movement :- Shown by only Lipids.  Lateral movement :- Shown by both Lipids and Proteins.  CELL : THE UNIT OF LIFE Transport of Molecules  One of the most important function of the plasma membrane is the transport of the molecules across it.  The membrane is selectively permeable to some molecules present on either side of it.  There are two types of transport :- I. Passive Transport (Downhill transport) :- A. Simple Diffusion :- The movement of molecules of a material from an area of higher concentration to an area of their lower concentration is called diffusion. Ex.- Neutral solutes  Osmosis :- Osmosis is defined as the diffusion of solvent (like water) from the solution of lower concentration to the solution of higher concentration ,When both are separated by a selectively permeable membrane.  CELL : THE UNIT OF LIFE B. Facilitated Diffusion :-  Diffusion of any substance depends upon solubility in main constituent of membrane i.e. Lipid.  Lipid soluble substance rapidly diffuse through the membrane. Substances which have Hydrophilic moiety i.e. polar molecules, find it difficult to pass through the membrane.  So need to simplify its movement or their movement has to be facilitated.  Membrane proteins provide space for transfer of these molecules. This process is called facilitated diffusion. II. Active Transport (Uphill transport) :-  Movement of molecules against the concentration gradient i.e. from lower concentration to higher concentration is known as Active transport.  It requires energy to pump the molecules against concentration gradient.  It is carried by Membrane proteins. Ex:- Pumps proteins e.g., Na+/K+ Pump.  CELL : THE UNIT OF LIFE 3. ENDOMEMBRANE SYSTEM While each of the membranous organelles is distinct in terms of its structure and function, many of these are considered together as an endomembrane system because their functions are coordinated.  The endomembrane system include A. Endoplasmic reticulum (ER) B. Golgi complex C. Lysosomes Trick :- V E G Lover D. Vacuoles Since the functions of the mitochondria, chloroplast and peroxisomes are not coordinated with the above components these are not considered as part of the endomembrane system.  CELL : THE UNIT OF LIFE A. Endoplasmic reticulum (ER) Secretion Lysosome Trans / Maturing / Concave face Golgi body Cisternae Cis / Forming / Convex face Lipid Protein SER RER Nucleus Ribosome (80s)  CELL : THE UNIT OF LIFE A. Endoplasmic reticulum (ER) Secretion Lysosome Trans / Maturing / Concave face Golgi body Cisternae Cis / Forming / Convex face Lipid Protein SER RER Nucleus Ribosome (80s)  CELL : THE UNIT OF LIFE ER :- A network of tiny tubular structures present in the cytoplasm. ER divide the intracellular space into two distinct compartment i.e. Luminal (inside ER) and extra luminal (cytoplasm) compartments. Components of E.R. :- 1. Cisternae -  Long, flattened and unbranched structure.  Form structure of RER. 2. Tubules -  Irregular, often branched tube like structure.  Form structure of SER.  Tubules may free or associated with cisternae.  CELL : THE UNIT OF LIFE 3. Vesicles - Membrane bound oval / spherical shape structures. Rough E.R. Smooth E.R. (Granular) (Agranular) Ribosomes Present (80s) Absent Ribophorin Present Absent (glycoprotein) Ribosome Ribophorin ER Components Mainly cisternae Mainly tubules Function Protein synthesis Lipid synthesis Secretion Steroid hormone synthesis (in animals) Glycogen metabolism (in animals)  CELL : THE UNIT OF LIFE Modifications of Endoplasmic reticulum Sarcoplasmic Reticulum It is modifications of SER Occurs in skeletal and cardiac muscles. Stores Ca++ Functions :- Muscle contraction. Microsomes These are fragments of E.R. associated with ribosomes. Ribosome These can be obtained by high speed centrifugation of cell. They do not exist as such in the living cell. Microsomes Function :- Study of in-vitro protein synthesis by scientist.  CELL : THE UNIT OF LIFE Functions of Endoplasmic reticulum 1. Protein synthesis. 2. Lipid synthesis. 3. Mechanical support. 4. Intracellular transport. 5. Cellular metabolism. 6. Formation of Nuclear membrane. 7. Formation of Lysosomes, GB and microbodies. 8. Detoxification Toxic Cytochrome P450 Non- toxic (present in SER)  CELL : THE UNIT OF LIFE B. Golgi complex Golgi body was first observed and named by :- Camillo Golgi (1898). Golgi body is also named as :- Golgi body  Lipochondria (rich in lipids)  Dictyosome (plant golgi body) The cytoplasm surrounding Golgi body has fewer or no other organelles. It is called Golgi ground substance or zone of exclusion. Golgi body is also called as Middle men of the cell. It is director of macromolecular traffic in the cell.  CELL : THE UNIT OF LIFE Components of Golgi body:- 1. Cisternae - Trans / Maturing / Concave face  Long, flattened and unbranched structure.  Diameter - 0.5 to 1 𝝁𝒎.  Varied number of cisternae are present in golgi body. Golgi body Cisternae  Cis and trans faces are entirely different but interconnected. 2. Tubules -  Irregular, often branched tube like structure. 3. Vesicles - Cis / Forming / Convex face  Membrane bound oval / spherical shape structures.  CELL : THE UNIT OF LIFE Functions of Golgi complex 1. Cell Secretion :- Export of macromolecules. Golgi body receives material from ER through cis face Chemically modified by golgi body including Glycosylation Formation of glycoproteins and glycolipids Packaging of materials and delivered either to the cellular targets or secreted outside the cell.  CELL : THE UNIT OF LIFE 2. Formation of Lysosomes :- Collective functions of ER and Golgi body. (As material of lysosomes are formed by ER and Packaging of material of lysosomes are done by Golgi body.) 3. Synthesis of cell wall material. 4. Cell plate formation. (Cell plate formed during cytokinesis in plants) Golgi vesicle 5. Formation of acrosomes during spermiogenesis. Cell Plate  CELL : THE UNIT OF LIFE C. Lysosome Lysosome is single membrane bound structure. It contains digestive (acid hydrolytic) enzymes. E.g. - Lysosome pH = 5  Lipases Enzymes  Proteases  Carbohydrases H+ Pump  Nucleases These enzymes digest lipids, proteins, ATP H+ ADP carbohydrates and nucleic acids. Optimally active at acidic pH (pH = 5) Cytoplasm  CELL : THE UNIT OF LIFE Present in all eukaryotic cell.  Exception :- in Mammalian RBC Large sized in - WBC Maximum found in - Fungus Absent in all prokaryotic cell. (But periplasmic space act as a lysosome in prokaryotic cell)  Formation of Lysosomes :- Golgi body + ER = Lysosome G ER L GERL system is associated with lysosomes. So lysosomes are also called as GERL complex.  CELL : THE UNIT OF LIFE Types of Lysosomes 1. Primary Lysosomes / storage granules :- These lysosomes store enzyme Acid Hydrolases in the inactive form. (Enzymes synthesized on ribosomes in cytoplasm) These are newly formed lysosome. 2. Secondary Lysosomes / Digestive vacuoles / Heterophagosomes :- These lysosomes formed by the fusion of primary lysosomes and phagosomes or pinosomes. These are secondary Lysosomes. 3. Tertiary Lysosomes / Residual bodies / Telolysosome :- Lysosomes containing undigested material are called residual bodies. These may be eliminated by exocytosis.  CELL : THE UNIT OF LIFE Functions of Lysosomes I. Intracellular digestion :- a) Heterophagy :- Digestion of foreign materials received in cell by phagocytosis and pinocytosis. b) Autophagy :- Digestion of old or dead cell organelles materials. Autophagic Lysosomes / Autophagic vacuoles / autophagosomes :- Autophagy also takes place during starvation of cell. Lysosomes containing cell organelles to be II. Extracellular digestion :- digested are known as Autophagosomes. a) In Fungus :- Extracellular digestion also occurs by fungal lysosomes. b) During Osteogenesis :- Lysosomes of osteoclast (bone eating cells ) dissolve unwanted part of bones.  CELL : THE UNIT OF LIFE III. Autolysis (Cellular digestion) :- Sometimes all lysosomes of a cell burst to dissolve the cell completely. So Lysosome are also called as suicidal bags of cell.  Autolysis occurs during :- a. Removal of old cells. b. Removal of unwanted organs of embryo. c. Metamorphosis :- Cathepsin (protein digesting enzyme) of lysosomes digests the tail of Tadpole of frog.  CELL : THE UNIT OF LIFE D. Vacuoles Single membrane bound space found in the cytoplasm of plant cell mainly. The membrane of vacuole is called as tonoplast. It is present in permanent cell with large size. In plant cells the vacuoles can occupy up to 90% volume of the cell. In meristem cell :- Absent but if present than size is very small. In animal cell :- Absent but if present than size is very small.  CELL : THE UNIT OF LIFE Tonoplast Cell Sap Vacuole helps in osmoregulation of the cell.  CELL : THE UNIT OF LIFE Contractile Vacuole Contractile vacuole helps in excretion and Contractile osmoregulation. Vacuole Ex:- Amoeba Food Vacuole Food Vacuole In many cells food vacuoles are formed by engulfing the food particles. Ex:- Protista  CELL : THE UNIT OF LIFE Mitochondria Mitochondria Mitochondria is a Double membrane bound structure. Form ATP by Oxidative phosphorylation and provide energy to the cell. Present in eukaryotic cell. In prokaryotic cell, the function of mitochondria is performed by Mesosomes.  It is Power house of cell.  It is called Cell within the cell.  It is most busy and active organelle in cell.  Mitochondria is called Semi autonomous cell organelles.  CELL : THE UNIT OF LIFE  Number :- Variable (depends upon physiological activity of cell.) Mitochondria  Usually plant cells have fewer mitochondria as compared to animal cell.  In higher animals maximum mitochondria are found in flight muscles of birds.  Size and shape are also variable.  Shape :- Sausage or Cylindrical.  Mitochondria stained by :- Janus green B. Without staining, it is not easily visible under the microscope. Diameter = 0.2-1.0 μm (average 0.5μm) Length = 1 - 4.1 μm  CELL : THE UNIT OF LIFE 1. Outer Membrane :- Outer Membrane Porin present Inner Membrane More permeable Enzyme present Contain more phospholipids and cholesterol. 2. Inner Membrane :- Porin absent Less permeable Inner compartment Peri Mitochondrial Enzyme present (Matrix) Space Inner membrane is folded towards matrix called Cristae. Cristae increase the surface area of inner membrane. Pin headed particle present on inner membrane is called oxysome.  CELL : THE UNIT OF LIFE Inner Membrane :- Has Oxysome or Elementary particles or F0 – F1 particles or ATP synthase Base (F0) PMS ADP + iP Head Stalk (F1) ATP Matrix Process Oxidative phosphorylation Inner Membrane Outer Membrane  CELL : THE UNIT OF LIFE 3. Outer Chamber / Peri Mitochondrial space / Inter membrane space :- Space between both membranes. Ribosome (70s) DNA Contains H2O (aqueous chamber) and enzymes. 4. Inner Chamber :- Space inside the inner membrane. It is also called Matrix. Matrix contains :- a. H2O (aqueous chamber) Inner compartment Peri Mitochondrial b. Maximum enzymes for Kreb’s cycle. (Matrix) Space Except Succinate dehydrogenase (Present in inner membrane ) c. DNA :- Single (only one), Double strand, circular, GC rich, Naked d. Ribosomes :- 70s  CELL : THE UNIT OF LIFE  Mitochondria is called Semi autonomous cell organelle. Qn. Why Mitochondria is called semi autonomous cell organelle ? Ans.- Inner Chamber of Mitochondria has less DNA, so it forms less RNA , so there is less protein synthesis. DNA ↓ → RNA ↓ → Protein ↓ Hence it does not synthesize all required proteins and shows dependency on main DNA for required protein synthesis. Functions of Mitochondria I. Formation of ATP:- Site of aerobic respiration. (as it has maximum enzyme of the cell) II. Cytoplasmic inheritance  CELL : THE UNIT OF LIFE Biogenesis of Mitochondria Biogenesis of Mitochondria means present time mein cell mein naya mitochondria ka kaise formation hoga, agar cell ko naya mitochondria banana ho ??  New Mitochondria arise from division (Binary Fission / Amitosis) of pre-existing mitochondria.  CELL : THE UNIT OF LIFE Origin of Mitochondria Endo-symbiotic origin from prokaryotic cells. Prokaryotic cell 70s 70s Prokaryotic cell Mitochondria DNA Double strand, Double strand, Circular, Circular, GC rich, GC rich, Naked Naked Ribosome 70s 70s Eukaryotic cell Division Binary Fission Binary Fission Mitochondria  CELL : THE UNIT OF LIFE Plastid Plastids are found in all plant cells and in euglenoides. These are easily observed under the microscope as they are large. They bear various specific pigments like chlorophyll and carotenoids. So main function of plastid is Photosynthesis and provide colour. Pigments Plastid But some plastid does not have pigments, so it store food. Based on the presence or absence and type of pigments plastids can be classified into 3 types :- Chloroplasts, Chromoplasts and Leucoplasts.  CELL : THE UNIT OF LIFE Chromoplast Chloroplast Leucoplast Pigments Pigments Carotenes and Chlorophylls, Absent Xanthophylls, carotenoids (Colourless plastids) Function Provide colour Photosynthesis Storage of food Lamellar Present Present Absent structures DNA DNA Present Present Present Lamella (Thylakoid) Double Present Present Present membrane  CELL : THE UNIT OF LIFE A. Chromoplast  Pigment :- Carotenoids (Carotene & Xanthophyll)  Fat soluble pigments.  Function :- Provide colour (Red, orange, Yellow)  Provide colour of Pericarp and petals.  Ex:- Red colour of tomato is due to lycopene pigment of Chromoplast. Red colour of carrot is due to beta - carotene pigment of Chromoplast.  CELL : THE UNIT OF LIFE B. Leucoplast  Pigment :- ABSENT(Colourless plastids)  Function :- Storage of food material  Three types :- I. Amyloplast :- Store :- Carbohydrate (Starch) Ex:- Potato II. Aleuroplast :- Store :- Proteins III. Elaioplast :- Store :- Oil  CELL : THE UNIT OF LIFE C. Chloroplast Dimension of Chloroplast :-  Pigment :- Chlorophylls, Carotenoids  Function :- Width = 2 - 4 μm Photosynthesis and provide green colour.  Location :- Mainly present at mesophyll cells of leaves. Length = 5 - 10 μm Mesophyll cell :- 20-40 per cell. Chlamydomonas (a green alga) :- 1 per cell  Chloroplast may be of various shapes like :- Spherical, oval, Lens, Discoid or even ribbon shaped.  CELL : THE UNIT OF LIFE Outer Membrane PPS Inner Membrane Stroma / Matrix Stromal Thylakoid / Stromal lamella / Stromal membrane Granum Thylakoid / lamella / membrane Ribosome DNA  CELL : THE UNIT OF LIFE Membrane of Chloroplast :-  Membrane of chloroplast surrounded by double membrane. 1. Outer membrane :-  Porin present  More permeable 2. Inner membrane :-  Porin absent  Less permeable  The space limited by inner membrane is called the stroma / matrix.  CELL : THE UNIT OF LIFE Components of Stroma :- a. Thylakoids:- Flatted membranous sacs are present in stroma called thylakoids. Thylakoids are arranged in stacks like the piles of coins called grana (singular : granum) Each chloroplast contains about 40-60 granum. Thylakoids of the different granum connected by Stroma lamellae or Fret channel or Stroma thylakoids.  CELL : THE UNIT OF LIFE Components of Stroma :- a. Thylakoids:-  A space inside thylakoid is called lumen.  Quantasome :- Group of about 250 - 400 molecules of various pigments (Chl-a, Chl-b, Carotenes, xanthophylls etc.) present in the thylakoid membrane is called as Quantasome. b. Enzyme:- Enzyme is present in the stroma to synthesize carbohydrate. (Dark reaction / calvin cycle) For the synthesis of various protein.  CELL : THE UNIT OF LIFE Components of Stroma :- c. DNA :-  Double strand  Circular  GC rich  Naked d. Ribosomes:- 70s type  CELL : THE UNIT OF LIFE  Chloroplast is called Semi autonomous cell organelle. Qn. Why Chloroplast is called semi autonomous cell organelle ? Ans.- Inner Chamber of Chloroplast has less DNA, so it forms less RNA , so there is less protein synthesis. DNA ↓ → RNA ↓ → Protein ↓ Hence it does not synthesize all required proteins and shows dependency on main DNA for required protein synthesis. Biogenesis of Chloroplast Biogenesis of chloroplast means present time mein cell mein naya Chloroplast ka kaise formation hoga, agar cell ko naya Chloroplast banana ho ??  By two method I. From Proplastid II. New Chloroplast arise from division (Binary Fission / Amitosis) of pre-existing plastid.  CELL : THE UNIT OF LIFE Origin of Chloroplast Prokaryotic cell (BGA) Endo-symbiotic origin from prokaryotic cells. 70s Prokaryotic cell Chloroplast DNA Double strand, Double strand, 70s Circular, Circular, GC rich, GC rich, Naked Naked Ribosome 70s 70s Division Binary Fission Binary Fission Eukaryotic cell Chloroplast  CELL : THE UNIT OF LIFE Ribosomes Chloroplast  Ribosomes were first observed by George Palade (1953).  So ribosomes are also called as Palade’s particles.  Ribosomes are smallest cell organelle. (size = 15-20 nm)  Ribosomes are membraneless cell organelle.  It is protein factory of the cell.  It is Universal cell organelles. Ribosome Except mammalian RBC, all living cells have ribosomes. (Both prokaryotes and eukaryotes)  Ribosomes are also called as ‘’Organelle within organelle’’ Mitochondria  CELL : THE UNIT OF LIFE Types of Ribosomes 70s type 80s type Present in both (i.e. Eukaryotic and Prokaryotic cell.) Present only in Eukaryotic cell in Prokaryotic cell Eukaryotic cell 1. Cytoplasm 2. On the surface of ER In Prokaryotic cell, 70s In Eukaryotic cell, 70s ribosomes are found in ribosomes are found in 1. Cytoplasm 1. Mitochondria 2. On the surface of plasma 2. Plastid (Chloroplast) membrane  CELL : THE UNIT OF LIFE  Ribosomes are composed of ribonucleic acid (r-RNA) and proteins. r-RNA + Proteins = Ribosomes Subunits of Ribosomes 70s type 80s type Larger Larger Smaller Smaller  CELL : THE UNIT OF LIFE  Minimum 0.001 M Mg++ concentration is required.  S =Svedberg unit or Sedimentation rate. It indirectly is a measure of density and size. Polyribosome / Polysome / Ergosome  CELL : THE UNIT OF LIFE Cytoskeleton  Filamentous  Proteinaceous structures,  Present in the cytoplasm.  It is involved in many functions such as :-  Mechanical support,  Motility,  Maintenance of the shape of the cell.  Cytoskeleton consists of A. Microtubules, B. Microfilaments and C. Intermediate filaments.  CELL : THE UNIT OF LIFE A. Microtubules  Microtubules composed of Tubulin proteins. Tubulin protein  Hollow structure. Microtubules  Diameter ≈ 25nm  Functions :-  Mechanical support.  Maintenance of cell shape. Basal body  Component of Cilia and Flagella (Motility). Cilia / Flagella  Component of Centriole.  Component of Spindle fibres (cell division). Spindle fibres  CELL : THE UNIT OF LIFE B. Microfilaments  Microfilaments composed of Actin proteins. Actin protein  Solid structure.  Diameter ≈ 6 - 7 nm  Functions :-  Mechanical support. Microfilaments  Maintenance of cell shape.  Muscle contraction.  Cell division in Animal cell (Cytokinesis). Furrow formation Microfilaments  CELL : THE UNIT OF LIFE C. Intermediate Filaments  Intermediate Filaments composed of Lamin proteins. Nuclear lamina  Solid structure.  Diameter ≈ 8 -12nm  Functions :-  Mechanical support. Nucleus  Maintenance of cell shape.  Form basket like structure around nucleus (nuclear lamina) and provide shape of nucleus.  CELL : THE UNIT OF LIFE Centriole  Membrane-less.  Cylindrical structure (Cart wheel structures in Centriole transverse section)  Present in cytoplasm of animal cell. Centriole Diplosome  Centrosome is absent in higher plants.  Centrosome containing two centrioles (Diplosome) which lie at right angle (900) to each other. Animal cell Cart wheel structure  CELL : THE UNIT OF LIFE Structure of Centriole Mussules  Centrioles mainly consist of 9 evenly spaced Peripheral Microtubules peripheral triplet fibrils of tubulin(Microtubules).  Arrangement :- 9 (Triplet) + 0 A- C Linker  These triplets are linked with the help of A-C linker. Hub  In central part, microtubules are absent. Radial Spoke  The central part of the centriole is proteinaceous and is called the Hub.  Hub is connected with peripheral triplets by Y thickening radial spokes made of protein. X-Y linker X thickening  Centrioles are self duplicating units.  CELL : THE UNIT OF LIFE Function of Centriole Cell Membrane 1. Centrioles form the basal body of cilia and Microtubules flagella. 2. It helps in cell division (By Attachment of spindle fibres between two poles of cell.) Basal body Cilia / Flagella Spindle fibres Centriole  CELL : THE UNIT OF LIFE Cilia and Flagella Flagella Cilia Paramecium Chlamydomonas Cilia Flagella The cilia are shorter (5 - 10 μm) The flagella are longer (upto 150 μm) More in number. Few in number. Cilia beat in a coordinated Flagella beat independently. manner. (pendular / oar like (Undulating movement) movement) Cilia take part in Locomotion Flagella take part in Locomotion. (cell / fluid), Attachment, Feeding and Sensation.  CELL : THE UNIT OF LIFE Structure of Cilia and Flagella Microtubules Cilia (singular : Cilium) Flagella (singular : Flagellum) Shaft Hair like outgrowths of the cell membrane. Prokaryotic bacteria also possess flagella but these are Basal body structurally different from that of the eukaryotic flagella. Cilia / Flagella They are covered with plasma membrane. Their core are called the axoneme. Axoneme possesses nine doublets of peripheral microtubules. It also has a pair of centrally located microtubules. Arrangement = 9 (Doublets) + 2 (singlet) is referred to as the 9+2 array.  CELL : THE UNIT OF LIFE Structure of Cilia and Flagella Cell Membrane Microtubules Peripheral Microtubules (Doublets) Shaft Axoneme A-B Linker (Interdoublet bridge) Central Sheath Basal body Dynein arm Cell Membrane Central Bridge Central Microtubules (Doublets) Radial Spoke  CELL : THE UNIT OF LIFE The peripheral doublets are interconnected by linkers. The central tubules are connected by bridges and is also enclosed by a central sheath. Central sheath connected to one of the tubules of each peripheral doublets by a radial spoke. Thus there are nine radial spokes. Both the cilium & flagellum emerge from centriole- like structure called the basal bodies or blepheroplast.  CELL : THE UNIT OF LIFE Microbody Microbody is SINGLE membrane bound minute vesicle. E Microbody contains various enzymes. E Microbodies are present in both plant and animal cells. E E E Types of Microbodies 1. Peroxisomes or Uricosomes Peroxisome is SINGLE membrane bound structure. Peroxisome contains various enzymes. Peroxisomes are found in both plant and animal cells.  CELL : THE UNIT OF LIFE Functions of Peroxisome :- I. β-oxidation :- Oxidation of fatty acids. II. Breakdown of Hydrogen peroxide (H2O2) :- H2O2 Catalase enzyme H2O + O2 Toxic Non - Toxic CO2 = Calvin cycle start III. Photorespiration (C2 / Glycolate pathway) :- RuBp O2 = Photorespiration start  Photorespiration process completed in 3 cell organelles i.e. Chloroplast, Peroxisome and Mitochondria (In sequence) RAMBAAN :- CPM  CELL : THE UNIT OF LIFE 2. Glyoxysomes Highly specialized Peroxisomes. Glyoxysome is SINGLE membrane bound structure. Glyoxysome is only present in plant. (Fatty seeds e.g. Castor seed. Function :- Glyoxylate cycle Fat Carbohydrate  CELL : THE UNIT OF LIFE Nucleus Nucleus was first discovered by Robert Brown (1831). Nucleus is double membrane bound structure. Nucleus is called as controller or director of the cell. Functions :-  Nucleus stores the genetic information of the cell.  Nucleus control heredity & inheritance.  Nucleus help in cell growth.  Nucleus help in cell metabolism.  Function of nucleus was experimentally proved by Hammerling. (He performed Experiment on Acetabularia, a single cell largest alga).  CELL : THE UNIT OF LIFE Number of Nucleus per cell I. Generally a cell has single nucleus (Uninucleated).  Example :- Most of eukaryotic cells  Nucleus ABSENT in II. Two nucleus per cell (Binucleated) a. Mature mammalian RBC  Example :- Paramecium b. Sieve tube cells of phloem III. More than two nucleus per cell (Multinucleated)  Example :-  Endosperm of angiosperm Question :-  Rhizopus  Would you consider Mature mammalian RBC & Sieve  Vaucheria tube cells of phloem as living ??  Ans.- Yes, because these cells are metabolically active.  CELL : THE UNIT OF LIFE Structure of Interphase Nucleus I. Nuclear membrane Chromatin II. Nucleoplasm III. Chromatin IV. Nucleolus Nucleolus Nucleoplasm Nuclear membrane  CELL : THE UNIT OF LIFE I. Nuclear membrane Cytoplasm Nucleoplasm RER RNA RNA Protein Protein Inner nuclear membrane Nuclear Lamina Ribosome (80s) Peri nuclear space (10-50 nm) Outer nuclear membrane Nuclear pore Nucleoplasmin protein  CELL : THE UNIT OF LIFE I. Nuclear membrane Cytoplasm  Nucleus surrounded by two membrane :- a. Outer membrane :- Nucleoplasm It is continuous with ER. It also bears ribosomes (80s). b. Inner membrane :- The inner side of inner nuclear membrane is Perinuclear space lined by nuclear lamina.  Perinuclear space :- A space between membranes of the nucleus. Inner membrane Size :- 10 - 50 nm Outer membrane  CELL : THE UNIT OF LIFE I. Nuclear membrane Cytoplasm  Nuclear pore:- Nuclear envelope is interrupted by minute pores called nuclear pore. Nucleoplasm It is formed by the fusion of its two membranes. The nuclear pore, is guarded by a octagonal discoid structure of Nucleoplasmin protein. Through nuclear pores, movement of RNA and protein molecules takes place in both directions.  Nuclear membrane is formed by E.R.  It disappears during Prophase and reformed Nucleoplasmin protein during Telophase. Nuclear pore  CELL : THE UNIT OF LIFE II. Nucleoplasm / Nuclear matrix :- Cytoplasm  Material present inside the nucleus is called nucleoplasm.  It contains :- Nucleoplasm Chromatin Enzymes. Nucleolus Nucleotides, Nucleosides, ATPs, Proteins Nucleoplasmin protein Nuclear pore  CELL : THE UNIT OF LIFE III. Chromatin (Nucleoprotein fibers) :- Cytoplasm  Chromatin term was given by Flemming.  He stained chromatin by the basic dye (Acetocarmine) Nucleoplasm  Chromatin consists of :- DNA RNA Histone protein (basic proteins, rich in Arginine and Lysine) and Non-histone proteins. Note :- DNA (Chromatin) Chromatin stained by Basic dye :- Acetocarmine CELL : THE UNIT OF LIFE III. Chromatin (Two types) :- Euchromatin & Heterochromatin Less Histone Loosely packed Less DNA Lightly stain Transcriptionally active More Histone Tightly packed More DNA Dark stain Transcriptionally Inactive  CELL : THE UNIT OF LIFE III. Chromatin :-  Heterochromatin :- 2 Types A. Constitutive heterochromatin :- Permanently inactive.  Ex:- Centromeric region B. Facultative heterochromatin :- Temporarily inactive. Ex:- Barr body in female.  CELL : THE UNIT OF LIFE IV. Nucleolus :-  Spherical.  Membraneless structure.  Present in the nucleoplasm.  Functions:- Nucleolus Nucleolus Formation of Ribosomes. Nucleolus is called Factory of Ribosomes. It is a site for active ribosomal RNA (r-RNA) Ribosomes synthesis. Larger and more numerous nucleoli are present in cells actively carrying out protein synthesis. Protein  CELL : THE UNIT OF LIFE Chromosome Chromosome is highly condensed form of the chromatin which is formed at the time of cell division. Condense Chromatin Chromosome Decondense Cell division During cell division, chromosomes appear at the place of nucleus.  CELL : THE UNIT OF LIFE  Chromatid :- At metaphase stage each chromosome consist of two cylindrical 1 structures called chromatids. Both sister chromatids are joined together by a common centromere. Each chromatid consist of a single long thread of DNA associated 2 with histone. 2.2 meter Non histone proteins and RNA are also present.  Best stage to study morphology of chromosome :- Metaphase  Best stage to study shape of chromosome :- Anaphase  A single human cell has approximately 2.2 meter long thread of 46 DNA distributed among its 46 (23 pairs) chromosomes.  CELL : THE UNIT OF LIFE Structure of Chromosome I. Primary constriction (Centromere):-  Every chromosome essentially has a primary constriction.  Outside centromere, a proteinaceous disc like structure is present called Kinetochore.  Each chromosome (at prophase or metaphase) consist of Kinetochore.  Kinetochore is the actual site of attachment of spindle fibres.  CELL : THE UNIT OF LIFE Structure of Chromosome II. Secondary constriction :-  Additional constriction found on few chromosome called secondary constriction.  Secondary constriction is also known as NOR (Nucleolar Organizer Region). (13,14,15,21,22 chromosomes in Human) Prophase Telophase Nucleolus Nucleolus NOR (Nucleolar Organizer Region) CELL : THE UNIT OF LIFE Structure of Chromosome  CELL : THE UNIT OF LIFE Structure of Chromosome III. Satellite :-  Part after NOR is called satellite and such chromosome is called SAT chromosome. IV. Telomere :-  End part of the chromosome is called Telomere.  It has single strand DNA.  It is Guanine rich (5’ - TTAGGG - 3’)  It is non sticky end.  It prevents fusion of chromosomes.  It is formed by telomerase enzyme (ribonucleoprotein).  Telomeres of chromosomes shorten during ageing process. Types of Chromosomes (Based on position of Centromere) q (long arm) Arm ratio = p (short arm) Sub-Metacentric Acrocentric Metacentric Telocentric  CELL : THE UNIT OF LIFE Karyotyping Karyotype :-  Study of morphology of all chromosomes of a cell.  Karyotype can be studied in Metaphase of mitosis.  Karyotype includes :-  The number of chromosomes.  Relative size.  Position of centromere.  Length of arms.  Secondary constriction.  CELL : THE UNIT OF LIFE Idiogram  Diagrammatic representation of karyotype.  In Idiogram, chromosomes are arranged in decreasing order of size.  Sex chromosomes are placed in last.  CELL : THE UNIT OF LIFE Special Types of Chromosomes A. Polytene Chromosome / Salivary Gland Chromosome:-  It was discovered by E.G. Balbiani, in salivary glands of Chironomous larva. Puffs Dark band  In this chromosome, number of chromatids are very high. Knob  In this chromosome, at some places, swollen areas are Inter band present which are called as Balbiani rings or puffs.  Balbiani rings or puffs helps in synthesis of RNA and RNA proteins. ↓ Protein  This proteins are concerned with Metamorphosis and ↓ Larva Adult Moulting process of insect larva. Metamorphosis  CELL : THE UNIT OF LIFE Special Types of Chromosomes B. Lampbrush Chromosome:-  Seen in oocytes of vertebrates (amphibian) during diplotene stage (prophase I of meiosis) of cell division.  Concerned with vitellogenesis (yolk formation).  CELL : THE UNIT OF LIFE “सीखने के विए जुनून पैदा कीवजये, यवद आप ऐसा करते हैं , तो आप कभी भी आगे बढ़ने से नही ीं घबराएीं गे”