The Discovery of Cells PDF

COURSE OUTCOME 1: THE DISCOVERY OF CELLS King Charles II of England (1661) Commissioned a microscopic examination of the natural world Robert Hooke (1635-1703) Satisfies his curiosity in examining bugs Devised one of the earliest microscopes Curator of Experiments for the Royal Socie...

COURSE OUTCOME 1: THE DISCOVERY OF CELLS King Charles II of England (1661) Commissioned a microscopic examination of the natural world Robert Hooke (1635-1703) Satisfies his curiosity in examining bugs Devised one of the earliest microscopes Curator of Experiments for the Royal Society of London (1662) First in seeing a cell (1666) Antony Van Leeuwenhoek First to study magnified cells Devised a simple microscope (1 lens) First to observe living cells (Animalcules) FACTORS THAT RESTRICTED THE UNDERSTANDING OF THE NATURE OF CELLS Limited Resolution (Resolving Power) Descriptive Nature of 17th-Century Biology THE CELL THEORY The cell is the basic unit of life All life forms are made up of one or more cells Cells come from pre-existing cells MICROSCOPES REVEAL THE MICROSCOPIC WORLD OF CELLS Microscopes Used to examine objects that are too small to be seen Light compound microscope Uses light and lenses to magnify up to 1500x larger Parts of a Microscope: Eyepiece/Ocular Lens Lens at top that you look through Usually 10x or 15x power Body Tube Connects eyepiece to objective lenses Arm Supports tube and connects it to the base  Base Bottom of the microscope Illuminator/Light Source Steady light source to reflect light up through bottom of stage Stage Flat platform to place slides Stage Clips Holds slide in place Revolving Nosepiece Holds two or more lenses and can be rotated to change power Objective Lenses Uses to further magnify specimen being observed ○ Scanning(4x) objective ○ Low Power (10x) objective - LPO ○ High Power (40x) objective - HPO ○ Oil Immersion (100x) objective Diaphragm/Iris Rotating disk under stage Used to vary intensity and size of cone of light Coarse Adjustment Knob Moves stage up and down Only used for scanner and LPO Fine Adjustment Knob Brings specimen to sharper focus for LPO Used for all focusing for HPO Micrograph Image produced by a microscope Magnification Measure of optical instruments Resolution Clarity of an image THE LEVELS OF ORGANIZATION ATOMS > MOLECULE > MACROMOLECULE > ORGANELLE > CELL > TISSUE > ORGAN > ORGAN SYSTEM > ORGANISM > POPULATION > SPECIES > COMMUNITY > ECOSYSTEM > BIOSPHERE CRITERIA FOR AN ENTITY TO BE ALIVE 1. Information 2. Metabolism 3. Membrane Characteristics of Life: (Mrs. Gren)  Movement Respiration Sensitivity Growth and Development Reproduction Elimination Nutrition —------------------------------------------------------------------------------------------------------------------------- IMPORTANT TERMS: Unicellular Organisms one cell for all functions Multicellular Organisms many cells to perform different functions to support the organism Prokaryotic Cells (Prokaryotes) pro (before), karyon (nucleus) Cells that lack a membrane-bound nucleus DNA is in the cytoplasm No membrane-bound organelles Eukaryotic Cells (Eukaryotes) Eu (true), karyon (nucleus) Cells that have a nucleus Contain other organelles besides nucleus Invagination of plasma membrane created nuclear envelope and a series fo organelles The Endosymbiotic Theory ○ Evolution of eukaryotic organelles by phagocytosis of prokaryotes ○ Mitochondria and chloroplasts were independent prokaryotes that took up residesnce in a eukaryotic cell —------------------------------------------------------------------------------------------------------------------------- CLASSIFICATION OF LIVING ORGANISMS Used to establish phylogenetic or evolutionary relationships of organisms Ex. The Five Kingdom Classification by R.H. Whittaker The Three Domains of Life by Carl Woese TWO-KINGDOM CLASSIFICATION Kingdom Plantae - Plants were (immobile) Kingdom Animalia - Animals were (moving) THREE-KINGDOM CLASSIFICATION Added: Kingdom Protista - single-celled microscopic organisms FIVE KINGDOM CLASSIFICATION Grouped based on :  Type of cell (prokaryotic or eukaryotic) Complexity (unicellular or multicellular) Type of nutrition Kingdom Plantae Kingdom Animalia Kingdom Fungi Kingdom Protista ○ Plant-like ○ Animal-like ○ Fungi-like Kingdom Monera (prokaryotes) ○ Archaebacteria ○ Eubacteria THE THREE DOMAINS OF LIFE There are two groups of prokaryotes rather than just Monera that should be in separate domains (category of classification higher than kingdom category) Domain Bacteria ○ Has prokaryotic cells Domain Archaea ○ Has prokaryotic cells that live in extreme environments Domain Eukarya ○ Has organisms with eukaryotic cells (protists, fungi, plants, animals) PROKARYOTES VS. EUKARYOTES Prokaryotes ○ Bacteria ○ Archaea (phylogenetically related) Eukaryotes  ○ Eukarya (phylogenetically related) DOMAINS BACTERIA, ARCHAEA, AND EUKARYA DIFFER FROM EACH OTHER IN MANY WAYS Presence of membrane-bound organelles and nucleus Exocytosis and endocytosis Organization of DNA Segregation of genetic information Expression of DNA PROKARYOTIC CELLS Lack nucleus Lack membrane-bound organelles Parts of a Prokaryotic Cell: Capsule - outer gelatinous covering Cell wall - provides shape, support and protection Plasma membrane - phospholipid bilayer with embedded proteins Ribosome - site of protein synthesis, composed of proteins and ribosomal RNA Pilus and fimbriae - cell attachments to surfaces and other cells Flagellum - for movement GENETIC MATERIAL Every cell contains DNA Prokaryotes Eukaryotes Contains a single circular molecule of DNA Contains DNA organized into linear (nucleoid) found near the center of the cell chromosomes segregated into a nucleus that is surrounded by a nuclear envelope EUKARYOTIC CELL Presence of organelles structures inside the cell that are surrounded by plasma membrane (except ribosome) Eukaryotic Cell Structures 1. Plasma Membrane (cell membrane, plasmalemma) Encloses a cell and separates its contents from its surroundings Regulates transport of materials into and out of the cell Involved in cell recognition, connection and adhesion, and cell communication 2. Nucleus Information center (contains genetic information) Made of inner and outer membrane Largest organelle in a eukaryotic cell Roughly spherical Located in the center of a cell First described by Robert Brown Site of DNA replication and transcription in eukaryotes Structure of a Nucleus: Nucleolus Site of rRNA synthesis Nuclear envelope Two phospholipid bilayer Nuclear pores  Regulates passage of molecules between nucleus and cytoplasm 3. Cytoplasm (cytosol) Semifluid matrix that fills up the cell Contains sugar, amino acids, and proteins the cell needs Contains membrane-bound organelles which ensures compartmentalization (endomembrane system membrane-bound organelles)in eukaryotes 4. Ribosomes Carry out protein synthesis (translation) Composed of large and small subunit of RNA and proteins Can form a polyribosome (a string of ribosomes simultaneously synthesizing same protein) Free Ribosomes (Synthesize proteins found floating in cytoplasm) Membrane-associated ribosome (synthesize proteins found in endomembrane system) 5. Endomembrane system Series of membrane in cytoplasm Divides cell into compartments Channels the passage of molecules through cell interior Provides surfaces for synthesis of lipids and proteins 6. Endoplasmic Reticulum Largest internal membrane Composed of phospholipid bilayer embedded with proteins Characterized by cisternae Two types: ○ Rough ER Ribosomes attached Synthesis of protein for export Contains enzymes that add sugar chains to proteins to form glycoproteins (glycosylation) ○ Smooth ER Does not have ribosomes attached Synthesis of lipids 7. Golgi Apparatus/Complex Consists of a stack of slightly curved, flattened saccules or sacs Processes proteins and lipids Can modify sugar chains attached to proteins Sorts modified molecules and packages them into vesicles Sides of Golgi Apparatus in animal cells: ○ Cis (inner face) Directed toward the ER ○ Trans (outer face) Directed toward the plasma membrane Protein Transport Through the Endomembrane System Proteins and lipids manufactured on the RER and SER are transported into the Golgi Apparatus and modified as they pass through it 8. Lysosome Lysis - destruction, Soma - body Digestive vesicles produced by Golgi Apparatus Contains high level of enzymes Performs autophagy (destroys nonfunctional organelles) Tay-Sachs disease - disease due to missing lysosomal enzyme 9. Peroxisome Contains enzymes to oxidize and breakdown fatty acids (produces hydrogen peroxide) Catalase - breaks down hydrogen peroxide Synthesize and break down lipids Also present in plant cells Adrenoleukodystrophy (ALD) ○ Disease due to lack of membrane protein ○ Damages brain, nervous system and adrenal gland 10. Vacuole Found in plant cells (central vacuole) Maintains tonicity and osmotic balance in plant cells Storage of useful molecules Breakdown of macromolecules Detoxification of foreign substance Protists have contractile vacuole - expels excess water Mitochondria and Chloroplasts Surrounded by double membrane Contains their own proteins synthesis machinery Involved in energy metabolism 11. Mitochondria Site of ATP (adenosine triphosphate) synthesis Converts chemical energy into a more useful form to be used by cells Two membranes ○ Outer (smooth) ○ Inner (folded) Cristae - numerous folded layers that divide mitochondrion into matrix and intermembrane space 12. Chloroplasts Found in plant cells only Site of photosynthesis Chlorophyll - gives green pigment to plants Has outer and inner membrane  Thylakoids - contains light-capturing photosynthetic pigments Grana - stacks of thylakoids Stroma - contains enzymes used to synthesize glucose 13. Cytoskeleton Protein fibers that support shape of cell and anchors organelles to fixed locations Types of fibers: ○ Actin filaments (microfilaments) - responsible for cellular movement ○ Microtubules - organizes the cytoplasm ○ Intermediate filaments - provide structural stability 14. Centriole Found in animal cells only Occur in pairs Centrosome - region surrounding the pair Composes of 9 triplets of microtubules EXTRACELLULAR STRUCTURES 1. Flagella and Cilia For movement 2. Plant cell walls Provide protection and support protective layer made of carbohydrate polymers ○ Primary Cell Wall - provides flexibility and allows cell to increase in size ○ Secondary Cell Wall - between primary cell wall and plasma membrane 3. Extracellular Matrix Protective layer over cell surface Provides animal cells strength to prevent tearing Participate in movement Scaffold where cells can organize themselves Cell signalling CELL-TO-CELL INTERACTIONS 1. Surface Proteins Give cell identity Cells read each other and react ○ Glycolipids - tissue-specific spell ○ MHC proteins - major histocompatibility complex 2. Adhesive Junctions Attaches cytoskeleton of cells to the extracellular matrix (ECM) 3. Septate/Tight Junctions Connects plasma membrane of adjacent cells in a sheet – no leakage 4. Communication Junctions Chemical or electrical signal passes directly from one cell to an adjacent cell (gap junction plasmodesmata) —------------------------------------------------------------------------------------------------------------------------- COURSE OUTCOME 2: THE CELL CYCLE Cell Cycle Events involving growth, synthesis, and regulations in a cell that results in cell division Cell Division Reproduction of cells Parent cell produce daughter cell Key Roles of Cell Division: Ability of organisms to reproduce distinguishes living to non-living things Integral part of cell cycle Unicellular organisms - reproduces entire organism Multicellular organisms - depend on cell division for: ○ Development of fertilized egg ○ Growth ○ Repair CELL DIVISION CAN RESULT IN GENETICALLY IDENTICAL DAUGHTER CELLS Mitosis Produces identical daughter cells (DNA) Meiosis Produces unique daughter cells (gametes) CELLULAR ORGANIZATION OF THE GENETIC MATERIAL All DNA has genome (can have a single DNA (prokaryotic cells) or many DNA (eukaryotic cells) Chromosomes Packaged DNA molecules PROKARYOTIC VS. EUKARYOTIC CELL DIVISION Prokaryotic Cell Division Binary Fission ○ Process that occurs in bacteria to reproduce themselves Clonal ○ Each cell produced is an identical copy The Evolution Of Mitosis ○ Mitosis evolved before binary fission Eukaryotic Cell Division Every eukaryotic species has a characteristic number of chromosomes ○ Somatic cells (nonreproductive) - 2 sets of chromosomes ○ Gametes (reproductive) - half as many chromosomes as somatic cells Eukaryotic chromosomes have chromatin - complex of DNA & protein that condenses during cell division Distribution of Chromosomes during Eukaryotic Cell Division ○ DNA is replicated and chromosomes condense ○ Each duplicated chromosome has 2 sister chromatids that separate at cell division ○ Centromere Waist of duplicated chromosome Where chromatids are attached ○ Chromatin DNA packed with proteins Types of Chromosomes: ○ Metacentric (centromere at the middle) ○ Submetacentric (centromere between middle and end) ○ Acrocentric (centromere close to end) ○ Telocentric (centromere at end) Chromosomes ○ Humans have 46 chromosomes (23 nearly identical) ○ Each chromosomes contain hundreds to thousands of genes (determines how a person’s body grows, develops, and functions) ○ Autosomes Numbered chromosomes (related to size) ○ Sex Chromosomes Determine biological sex and sex-inked traits ○ Haploid (n) One complete set of chromosomes Has one copy of genome (complete DNA set) ○ Dipload (2n) Twice the haploid Total number of chromosomes in cell Has two copies of genome ○ Homologous Chromosomes Maternal and paternal copies of the same chromosome ○ Sister chromatids Replicas of a single chromosome held by centromeres Karyotyping ○ Karyotype Array of chromosomes an individual organism possess OVERVIEW OF CELL CYCLE/CELL DIVISION Eukaryotic Cell Division Has mitosis (division of nucleus) Has cytokinesis (division of cytoplasm) Meiosis (produces gametes) Produces non-identical daughter cells that have one set of chromosomes PHASES OF CELL CYCLE Mitotic (M) Phase Mitosis and cytokinesis Mitosis Nuclear division Occurs in somatic cells Produces two identical daughter cells Divided to 5 phases: ○ Prophase Chromosomes appear as 2 sister chromatids Cytoskeleton dissasembles Spindle fiber form Golgi apparatus and ER disperse Nuclear envelope breakdown ○ Prometaphase Chromosomes attach to spindle Chromosomes move to equator Centrosomes move towards opposite poles ○ Metaphase All chromosomes aligned at equator of cell ○ Anaphase Chromosomes ar pulled apart by spindle fiber ○ Telophase Nuclear envelopes form Golgi apparatus and ER form Spindle fiber disassembled Cytokinesis Division of cytoplasm Results 2 daughter cells from one parent cell Underway by late telophase Interphase Cell growth and copying of chromosomes for cell division 90% of cell cycle Divided into subphases: ○ G1 phase (first gap) - growth of cell  ○ S phase (synthesis) - chromosomes duplicate here ○ G2 phase (second gap) - double checks errors Mitotic Spindle Controls chromosomes movement during mitosis Produced during prophase in centrosome Contains centrosomes, spindle microtubules, and aster Attaches to kinetochores to move chromosome during prometaphase Chromosomes line up at center (metaphase plate) at metaphase Aster Extends from each centrosome IMPORTANCE OF MITOSIS: Necessary for growth and development of organism CELL CYCLE REGULATION (CHECKPOINTS) G1 checkpoint ○ If completed, it will complete S, G2 and M phases ○ If not, cell enters G0 phase (death of cell) Two types of regulatory proteins ○ Cyclins and Cyclin-dependent kinases (Cdks) ○ MPF (maturation-promoting factor) Cdks complex that triggers cell’s passage past G2 checkpoint into M phase STOP AND GO SIGNALS Internal signal Ex. ○ kinetochore not attached to spindle sends signal to delay anaphase External Signals ○ Growth factors, proteins Ex. ○ Platelet-derived growth factor (PDGF) stimulates division of human fibroblast cells ○ Density-dependent inhibition, crowded cells stop dividing LOSS OF CELL CONTROL Cancer Cells ○ Do not respond normally to body’s control mechanism ○ May not need growth factors to grow and divide ○ Anything that damages DNA lead to mutation  Cancer ○ Uncontrolled cell division Benign tumor - remain at original site Malignant tumor - spreads (metastasize) Proto-oncogenes ○ Normal cellular genes that become oncogenic (cancerous) when mutated ○ One allele mutated Tumor-suppressor genes ○ Both allele mutated P53 gene ○ Guardian of genome ○ Promotes apoptosis (cell death) MEIOSIS Occur in gametes Produces 4 unique daughter cells Occurs after interphase 2 divisions: ○ Meiosis I ○ Stages: Prophase I Chromosomes condense Spindle fibers form Crossing over occurs (genetic recombination) Metaphase I Pair of chromosomes align at the center Anaphase I Chromosome pairs are pulled apart Telophase I Nuclear envelope reform Separated chromosome form cluster Results in half the number of chromosomes of original cell ○ Meiosis II ○ Stages: Prophase II New spindle fibers forms Nuclear envelope breaks down Metaphase II Sister chromatids align at center Kinetochores attach to kinetochores of chromatids Anaphase II Sister chromatids are pulled apart Telophase II Nuclear membranes reform  Results in 4 haploid cells SEXUAL LIFE CYCLE IN ANIMALS Sexual Reproduction Reproduction that involves meiosis and fertilization (syngamy) COURSE OUTCOME 3: TRANSPORT OF MOLECULES ACROSS SELECTIVELY PERMEABLE MEMBRANE Membrane Lipids: The FLUID part of the model Phospholipids (Glycerophospholipids) = Glycerol + Phosphate Group + Fatty Acid chains Membrane Proteins: The MOSAIC part of the model Proteins Polymers of amino acids (polypeptide – string of amino acids bonded by peptide bond) Transport The ability of cells to move ions and molecules across membranes selectively Molecules that may pass the phospholipid bilayer Small & Large Hydrophobic Molecules - non-polar Small uncharged Polar Molecules (some) Large Uncharged Polar Molecules (some) Small Electrically Charged (cannot) The movement of ions are determined by its electrochemical gradient (combination of electrical and concentration gradient) MOLECULES CROSS MEMBRANE BY SIMPLE DIFFUSION, FACILITATED DIFFUSION, AND ACTIVE TRANSPORT Transport across a selectively permeable membrane Diffusion or Passive Transport does not require energy to move molecules to equilibrium ○ Simple Diffusion unassisted movement down the gradient ○ Facilitated Diffusion protein-mediated movement down the gradient Uses transport proteins Active Transport Protein-mediated movement up the gradient (against) Low to higher concentration Requires energy from ATP Sodium-potassium pump ○ PISO (potassium in–sodium out) ○ K = 2, Na = 3 Bulk Transport  Occurs by exocytosis and endocytosis (phago–food, pino–liquid/small, receptor-mediated endocytosis–correct fit) Osmosis Diffusion of water across a selectively permeable membrane Movement of water from high to low water concentration Movement of water from low to high solute concentration Tonicity Strength of solution in relation to osmosis ○ Hypotonic Water enters cell swell ○ Hypertonic Water exits cell shrink ○ Isotonic Water exit and enter cell normal