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Cell
 

Cell

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    Cell Cell Presentation Transcript

    • The Cell
    • Antoni van Leeuwenhoek
        • (1632-1723), Dutch, maker of first single lens microscope
        • The first to document the structure of RBC & the nature of the circulatory system
        • protozoans & bacteria, life cycles of many species of insects.
        • MICROMETER ( µ m) = 1/1000
    • Types of Microscopes
          • 1. COMPOUND/LIGHT MICROSCOPE
          • Principle: sunlight (light source)
          • 2. ELECTRON MICROSCOPE
          • Principle: beam of electrons
        • a. Transmission (magnification: >/=1Mx)
        • b. Scanning – 3D image <250,000x
        • Magnification = extent to which an image is enlarged
    •  
    •  
    • Image under Compound microscope Scanning EM Transmission EM
    • CELL
      • Robert Hooke (1665) = studied the cork & other plant materials  many small partitions separating
      • cavities  cells.
      • Basic structural and functional units of an organism
      • Carry out all chemical activities
      • needed to sustain life
    • Cell Diversity
      • Cells that connect body parts
      • Cells that cover and line body organs
      • Cells that move organs and body parts
      • Cell that stores nutrients
      • Cell that fights disease
      • Cell that gathers information and controls body functions
      • Cells of reproduction
    • 3 Main Parts
      • 1. PLASMA MEMBRANE
      • 2. CYTOPLASM
      • 3. NUCLEUS
    • 1. Plasma Membrane
      • syn: plasmalemma, cell membrane
      • - outer covering of the cell
      • - surrounds each cell  separate its contents from external environment
      • - regulates what enters & leaves the cell
      • - allows communication
    • Plasma Membrane
      • some, cholesterol and glycolipids
      • LIPID BILAYER + integral and peripheral proteins
      • SELECTIVE PERMEABILITY
        • - water & nonpolar (lipid-soluble) molecules e.g. FA, fat-soluble vit., steroids, O2, CO2
      • mainly made up of phospholipids and proteins (latter, mainly glycoproteins)
    • Plasma Membrane
      • Impermeable to: ions, glucose, a.a.
      • transport assisted by: ion channels, transporters
      • Integral proteins act as: receptors, enzymes, cell identity markers
    • Plasma Membrane
    • rane
    • Definition of Terms
      • Intracellular fluid (ICF) – inside body cells i.e. fluid in cytoplasm, 2/3 of body fluid
      • Extracellular fluid (ECF) – fluid outside body cells
      • Interstitial fluid – the ECF between cells
        • e.g. plasma (in blood vessels), lymph (in lymphatic vessels)
        • ** materials dissolved in body fluids: gases, nutrients, ions, etc.
    • Definition of Terms
      • Solute – any material dissolved in a fluid
      • Solvent – fluid in w/c the solute is dissolved e.g. water
      • Solution – homogenous mixture of 2 or more components (e.g. air, seawater, alcohol)
    • Definition of Terms
      • CONCENTRATION – the amount of a solute in a solution
      • CONCENTRATION GRADIENT – difference in concentration between 2 different areas
        • moving down vs. moving up
    • Substances move across cellular membranes by:
      • PASSIVE PROCESSES – substance moves down its concentration gradient using only its own energy of motion (kinetic energy)
        • SIMPLE DIFFUSION, OSMOSIS
      • ACTIVE PROCESSES – cellular energy (e.g. ATP) is used to push the substance through the membrane against its concentration gradient
        • ACTIVE TRANSPORT, VESICLES
    • Passive Processes
      • DIFFUSION – a substance moves from one place to another due to the substance's kinetic energy
          • particles move from a region of higher to lower concentration
          • endpoint: EQUILIBRIUM – substance is evenly distributed throughout the solution and the concentration gradient disappears
          • may or may not involve a membrane
    • Diffusion
    • 2 Types of Diffusion
      • 1. SIMPLE DIFFUSION
        • lipid-soluble substances diffuse through the lipid bilayer e.g. O2, CO2, N, f.a., steroids, vit. ADEK, H2O, urea
        • used in: exchange of gases, absorption of nutrients, release of wastes
    • Simple Diffusion
    • 2 Types of Diffusion
      • 1. SIMPLE DIFFUSION
        • Ion channels – allow a specific type of ion to move across the membrane through the channel's pore
        • e.g. K, Cl, Na, Ca
    •  
    • 2 Types of Diffusion
      • 2. FACILITATED DIFFUSION
        • an integral membrane protein assists a specific substance across the membrane
        • substance binds to a specific TRANSPORTER on one side of the membrane --> released on the other side after the transporter undergoes a change in shape
        • movement along a conc. gradient, NO ATP needed
        • e.g. glucose, fructose, galactose
    •  
    • Passive Processes 2. OSMOSIS = net movement of water through a selectively permeable membrane - water moves from an area of higher water to an area of lower water concentration - or, from an area of lower solute concentration to an area of higher solute concentration OSMOTIC PRESSURE – depends on the concentration of its solute particles - the higher the solute conc., the higher the osmotic pressure
    • Osmosis
    • EFFECT of OSMOSIS in CELLS ISOTONIC = any solution in w/c cells maintain their normal shape and volume, concentrations of solutes are same on both sides = tissue fluids, blood plasma, 0.9% NSS, 5% dextrose (glucose) HYPOTONIC = lower concentration of solutes (higher conc. of H2O) than the cytosol inside the cell = cell swells --> ruptures HYPERTONIC = higher concentration of solutes (lower conc. of water) than the cytosol inside the cell = cell shrinks
    • Effects of Osmosis
    • Passive Processes 3. FILTRATION = process by w/c H2O and solutes are forced through a membrane (or capillary wall) by fluid or hydrostatic pressure (pressure gradient) e.g. filtering capacity of the kidney (e.g. in urine formation)
    • Active Processes 1. ACTIVE TRANSPORT - cellular energy is used to transport substances across the membrane against a concentration gradient (from an area of low to an area of high concentration), needs ATP - splitting of ATP changes the shape of a transporter protein (PUMP) --> moves a substance across the membrane against its conc. gradient - Na, K, H, Ca, I, Cl
    • Active Transport
    • Active Processes 2. TRANSPORT IN VESICLES - VESICLE – small round sac formed by budding off from an existing membrane - transport substances, take in and release substances - requires energy (ATP)
    • 2 Types of Transport in Vesicles 1. ENDOCYTOSIS – materials move into a cell in a vesicle formed from the plasma membrane - substances are surrounded by a piece of the plasma membrane w/c buds off inside the cell to form a vesicle containing the ingested substances.
      • 1. PHAGOCYTOSIS – large solid particles (e.g. bacteria, viruses, aged or dead cells), are taken in by the cell
      • - fuses w/ a lysosome --> break down of material
      • - e.g. WBCs, macrophages
      2 Types of Endocytosis
      • 2. BULK-PHASE ENDOCYTOSIS (PINOCYTOSIS) – cells take up tiny droplets of ECF
      • - fuses with a lysosome --> enzymatic breakdown of engulfed solutes
      2 Types of Endocytosis
    • 2 Types of Transport in Vesicles 2. EXOCYTOSIS – results in secretion (release of materials from a cell) a. SECRETORY CELLS – release digestive enzymes, hormones, mucus, etc. b. NERVE CELLS – during release of neurotransmitters * membrane-enclosed secretory vesicles form inside the cell, fuse w/ the cell membrane, and release contents into the ECF
    • Exocytosis
    • Table. 3.2
    • Specializations of the Plasma Membrane
      • Microvilli
      • Membrane junctions
    • Membrane Junctions
      • 1. TIGHT JUNCTIONS = formed from fusion of adjacent cell membrane --> impermeable or leak-proof sheets
        • = keep digestive juices & harmful substances from damaging the organs or getting into the bloodstream
      • 2. DESMOSOMES = anchoring junctions (button-like thickenings), prevent cells under mechanical stress from being pulled apart e.g. skin
      • 3. GAP JUNCTIONS = allows communication e.g. heart, nervous system
    • 2. Cytoplasm
      • consists of all cellular contents bet. the cell membrane and nucleus
      • Includes:
        • CYTOSOL (ICF) – fluid portion of the cytoplasm, 55% of total cell volume, 75-90% H2O, site of chemical reactions
        • ORGANELLES – specialized structures inside cells w/ specific functions
    • 1. Cytoskeleton
      • network of 3 different types of protein filaments
      • 1. MICROFILAMENTS – thinnest, concentrated at the periphery --> strength and shape
      • - provides mechanical support and generates movement
      • - anchor cytoskeleton to integral proteins
      • - support for microvilli
      • - intercellular attachment
    • 1. Cytoskeleton 2. INTERMEDIATE FILAMENTS – found in parts of cells subject to tension (stretching), hold organelles in place, intercellular attachment 3. MICROTUBULES – long, hollow tubes, determines cell shape, movement of organelles w/in the cell, migration of chromosomes during cell division, movement of cilia and flagella
    •  
      • found near the nucleus
      • Includes:
      • 1. Centrioles (paired) – composed of microtubules
      • 2. Pericentriolar material – composed of tubulins, organizing centers for growth of the mitotic spindle (role in cell division)
      2 . Centrosome
    • 3. Cilia and Flagella
      • CILIA – short, hairlike projections extending from the surface of the cell
        • propel fluids across surfaces of cells
      • FLAGELLA - move an entire cell
    • 4. Ribosomes
      • Tiny, round, dark bodies
      • Actual site of protein production
      • high rRNA content
        • Free ribosomes
        • attached to RER
    • 5. Endoplasmic Reticulum (ER)
      • network of folded membranes
      • 2 Types
      • Rough ER – extends from the nuclear envelope, studded w/ ribosomes, synthesis of secretory proteins and membrane molecules
      • Smooth ER – extends from the RER --> network of membranous tubules, lacks ribosomes, f.a. & steroids (e.g. estrogen, testosterone) are produced, detoxification (e.g. alc, pesticides, carcinogens)
    • 5. Endoplasmic Reticulum (ER)
    • 6. Golgi Complex
      • Stack of flattened membranous sacs
      • Modify and package proteins
        • secretory vesicles
        • carries proteins and phospholipids to become part of cell membrane
        • incorporated in lysosomes
    •  
    • 7. Lysosomes
      • membrane-encosed vesicles, >/= 60 digestive enzymes
      • digestion, recycling
      • autophagy, autolysis
    •  
    • 8. Peroxisomes
      • Sacs containing oxidase enzymes
      • Use oxygen to detoxify harmful or poisonous substances (e.g. alcohol, formaldehyde)
      • Disarm “free radicals”
        • FR -> H2O2->H2O
        • liver and kidney cells
    • 9. Proteasomes
      • continuous destruction of unneeded , damaged or faulty proteins
      • contain proteases
    • 10. Mitochondria
      • powerhouse of the cell (site of ATP production)
      • increased in: muscles, liver, kidneys
    • 3. Nucleus
      • most prominent feature of a cell
      • NUCLEAR ENVELOPE – separates the nucleus from the cytoplasm
      • NUCLEAR PORES – control movement of substances
      • NUCLEOLI – sites of assembly of ribosomes
    • 3. Nucleus
      • GENES – hereditary units
        • direct cellular activities
        • arranged along chromosomes
          • 46 chromosomes (23/parent)
          • in a nondividing cell, chromosomes appear as diffuse granular mass --> CHROMATIN
      • GENOME – total genetic information carried in a cell or organism
    •  
    •  
    •  
    • Protein Synthesis
      • DNA found in genes gives instructions for making proteins
      • 1. Transcription – DNA is copied --> RNA
      • 2. Translation – information in RNA (attached to a ribosome) is translated into a sequence of a.a. --> protein molecule
    • Transcription
      • occurs in the nucleus
      • genetic info in DNA base triplets is copied into complementary sequence of CODONS in a strand of RNA (helped by RNA polymerase)
      • PROMOTER – sequence of nucleotides in DNA where RNA polymerase attaches to
      • TERMINATOR – sequence of nucleotides in DNA where transcription ends
    • 3 Kinds of RNA
      • 1. Messenger RNA (mRNA ) – directs synthesis of a protein
      • 2. Ribosomal RNA (rRNA) – joins w/ ribosomal proteins to make ribosomes
      • 3. Transfer RNA (tRNA) – binds to an a.a. and holds it in place on a ribosome until it becomes part of a protein during translation
    • Base pairing
    • Translation
      • mRNA attaches to ribosomes and directs protein synthesis by converting sequence of nucleotides (CODON) into a specific sequence of a.a. --> PROTEIN
      • tRNA contains the triplet of nucleotides called ANTICODON
      • Protein synthesis ends when ribosome reaches a STOP CODON
      • 15 a.a./second
    •  
    • Somatic Cell Division
      • process by which damaged, diseased or worn out cells are replaced
      • process by which cells reproduce themselves
    • 2 Types of Cell Division
      • 1. REPRODUCTIVE CELL DIVISION (MEIOSIS)
      • - the process that produces gametes (sperm & oocytes)
      • 2. SOMATIC CELL DIVISION
      • - division of all body cells (except gametes) --> two identical cells
    • Prerequisite of somatic cell division: DNA Replication
      • DNA – building blocks “nucleotides”
        • Deoxyribose sugar
        • Phosphate group
        • Nitrogen-containing base
      • duplication of the DNA sequences that make up the genes and chromosomes --> daughter cells w/ same genes and same number of chromosomes
      Prerequisite of somatic cell division: DNA Replication
    • DNA Replication
    • Cell Cycle
      • sequence of changes that a cell undergoes from the time it forms until it duplicates its contents and divides into two cells
      • 2 MAJOR PERIODS
      • 1. INTERPHASE – cell is not dividing
      • 2. MITOTIC PHASE – cell is dividing
      • DNA replication occurs
      • manufactures organelles and cytosolic components
      • increased metabolic activity
      • cell is growing
      Interphase
    • Mitotic Phase
      • consists of:
      • MITOSIS – nuclear division
      • CYTOKINESIS – cytoplasmic division into 2 cells
      • PROPHASE = chromatin coil and shorten  chromosomes, bar-like bodies
        • Chromosome = 2 strands of chromatids , held together by a buttonlike body, centromere
      Mitosis
      • Mitosis
      • STAGES :
      • METAPHASE – chromosomes cluster and align at the center (metaphase plate)
      • Mitosis
      • STAGES:
      • ANAPHASE – movement of chromosomes toward opposite ends of the cell
      • Mitosis
      • STAGES:
      • TELOPHASE – chromosomes uncoil and become chromatin again, nuclear envelope forms around each chromatin mass
    • Cytokinesis
      • division of a cell's cytoplasm and organelles
      • formation of cleavage furrow that extends around the center of the cell
      • endpoint: 2 new and separate cells
    •  
    • END
      • QUIZ NEXT MEETING!