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The cell Cell theory The cell is the smallest unit of life All living things are made up of 1 or more cells Cells come from pre-existing cells Science and technology evolve together microscope Microscopic exam Light microscope = light passes through lens to maginfy object Resolution = ability to distinguish between two points clearly Two types of cells Prokaryotes (pre cells) Domains bacteria and archaea Kingdom Monera Eukaryotes (true cells) Domain Eukarya Kingdoms protista fungi plantae animalia Most cells same size Allows for > surface area / volume Prokaryotes Domains bacteria and archeae Kingdom Monera Bacteria and cyanobacteria (blue-green algae) Smallest cells No membrane bound organelles NO NUCLEUS Cell walls as well as cell membranes Eukaryotes ALL other living things Domain Eukarya Kingdon Protista, Fungi, Plantae, Animalia Highly complex and organized Membrane bound organelles distribute ‘division of labor’ DNA in a nucleus Plant cell Cell wall Large central vacuole chloroplasts vs. animal cell centrioles Non membrane organelles In BOTH prokaryotes and eukaryotes CELL MEMBRANE (plasma membrane) Separates inside of cell from outside of cell Selectively permeable Phospholipid bilayer Amphipathic (hydrophobic and hydrophillic parts) Hydrophyllic phosphorus ‘heads’ Hydrophobic lipid ‘tails’ (early formation of micells) Cell membrane Fluid mosaic model Phospholipid bilayer not ‘locked’ in place Phospholipids may move laterally or flip flop Cholesterol Imbedded in phospholipid bilayer to help Stabilize fluidity and Prevent solidification in lower temperatures Cell membrane Fluid mosaic model Transmembrane proteins within phospholipid bilayer Why proteins? Proteins (in addition to cholesterol) help stabilize fluidity of phospholipid bilayer Act as markers for cell identification Selective control of what enters/exits cell diffusion Small uncharged particles enter/exit a cell via diffusion Movement is down a concentration [ ] gradient diffusion From area of [ ] to an area of [ ] Movement via diffusion is passive transport DOES NOT REQUIRE ENERGY Osmosis = diffusion of water through a semipermeable membrane Water moves towards side with a lower water [ ] aquaporins osmosis Hypertonic solution Solution has higher concentration of solutes Water diffuses out of cell Hypotonic solution Solution has lower concentration of solutes Water diffuses into cell Osmosis in plant and animal cells In hypotonic solutions Plant cells become turgid due to osmosis Animals cells lyse In hypertonic solutions Plant cells become flaccid due to osmosis Plasmolysis = cell membrane separates from cell wall causing cell death Animals cells crenated Cell membrane proteins Peripheral proteins (not embedded in lipid bilayer) Integral proteins (embedded in lipid bilayer) May be transmember proteins Transport proteins Move large or charged particles down a concentration gradient = facilitated diffusion (passive transport) Passive transport (facilitated diffusion) DOES NOT REQUIRE ENERGY Gated channels allow diffusion of specific solutes (ie. Na Stimulated to open by electrical or chemical stimulus more transport proteins Membrane proteins may move charged or large particles Across the phospholipid bilayer AGAINST the Concentration gradient. Active transport REQUIRES ENERGY From area of [ ] [ ] Sodium potassium pump Membrane potential Inside of cell has slightly negative charge Outside of cell has slightly positive charge Electrochemical gradient drives transport of ions across cell membranes Electrogenic pump = protein that generates voltage as it transports substances across the membrane Na / K pump H+ pump Some proteins are cotransporters Specific particles ‘sneak in’ behind/with others Enzymes and receptor proteins enzymes Sequential enzymes in metabolic pathways may be embedded in cell membrane to enhance efficiency of pathway Receptor site Binding site for extracellular chemical messenger (ligand) Signal-transduction pathway Extracellular 1st messenger activates receptor protein Receptor protein relay protein Relay protein stimulates effector protein (an enzyme) Enzyme product = 2nd messenger 2nd messenger triggers metabolic or structural response within cell Endocytosis / exocytosis 3 types of endocytosis Phagocytosis Pseudopods wrap around particles to form vacuoles of ‘food’ Pinocytosis Psuedopods enguf extracellular fluid Receptor mediated endocytosis Ligands stimulate receptor proteins on cell membrane to engulf extracellular particles via endocytosis (LDL cholesterol) Exocytosis = cell products exported from cell via vacuoles and endomombrane system junction proteins Intercellular junctions Join membranes of adjacent cells together In animals: Tight junctions Cell membranes from neighboring Cells are fused together Forms a seal between Cells. Ie epithelial cells Desmosomes Anchoring junctions. Hold cells together In sheets. Ie epithelial cells Gap junctions Communicating junctions. Provide for Cytoplasmic channels between cells. Plant cells Plasmodesmata = channels between plant cell walls and membranes Cell-cell recognition Glycoproteins identify cells to other cells Immune system Anchor proteins integrins Attach to cytoskeleton and ECM (extracellular matrix) Bound to actin or other cytoskeleton parts. Maintain cell shape . Fix member proteins in place. Attach to ECM to coordinate intracellular and extracellular changes ECM Glycoproteins (i.e. collagen, proteoglycans, integrins) secreted by cell. Provide anchorage and support for cells. Influence cells in embryonic development Control activity of genes in nucleus??? Cell wall Found in plants, fungi, bacteria and some protista but NOT in animal cells Plant cell walls made of cellulose Primary cell wall secreted by young plant cells Middle lamella = pectins between cell walls of 2 cells ‘glues’ 2 cells together Secondary cell wall secreted by some plants (in many layers) Plasmodesmata = openings between cell walls of adjacent cells Fungi cell wall made of chitin Bacterial cell wall made of peptidoglycan Ribosomes and cytoplasm ribosomes Protein complexes and RNA involved in protein synthesis In cytoplasm of prokaryotes and eukaryotes On the surface of rough ER in eukaryotes cytoplasm Region between cell membrane and nucleus in eukaryotes; Between nucleoid region and cell membrane in prokaryotes Cytosol = semi-fluid, gel like substance (same) cytoskeleton Nucleoid region = area of DNA concentration in prokaryotes Network of protein fibers in cytoplasm cytoskeleton Network of protein fibers in cytoplasm Maintain cell shape Anchor organelles Provide for MOVEMENT microfilaments Actin Intermediate filaments microtubules Hollow tubes from -tubulin and -tubulin dimer Radiate from centrosome near nucleus (eukaryotes) Centrioles made of 9 sets of triple microtubules. Involved in cell division (animal cells) Flagella and cilia For movement Cilia are short and numerous Flagella are long and few oars tail Animals and protists Animals, protists some plant sperm Specialized arrangement of microtubules allow flagella and cilia to move 9 doublets of microtubules in a ring with 2 microtubules in the center = ‘9 + 2’ pattern Basal body structured as a centriole anchors cilia/flagella to cell Dynein = motor molecule (protein) between microtubule doublets that uses ATP To move flagella/cilia ‘walking’ Movement within cells Microfilaments actin and myosin slide past one another when a muscle cell contracts Microfilaments actin and myosin involved in amoeboid movement (use of pseudopods) Microfilaments actin and myosin involved in cytoplasmic streaming cytoplasmic streaming Sordaria sp Intermediate filaments more permanent for structure. Diverse class of proteins in keratin protein family.
