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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!