* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 6: A Tour of the Cell The Cell Theory • All living organisms
Survey
Document related concepts
Cell culture wikipedia , lookup
Cell encapsulation wikipedia , lookup
Cellular differentiation wikipedia , lookup
Cell growth wikipedia , lookup
Extracellular matrix wikipedia , lookup
Cytoplasmic streaming wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Signal transduction wikipedia , lookup
Cell membrane wikipedia , lookup
Cytokinesis wikipedia , lookup
Cell nucleus wikipedia , lookup
Transcript
Chapter 6: A Tour of the Cell The Cell Theory All living organisms are made of cells Cell is the basic functional unit of life All cells arise from previously existing cells Microscopy Light microscope (LM) – visible light passes thru specimen & then glass lenses Electron microscopes – for subcellular structures o Scanning EM (SEM) – focus beam of electrons onto surface of specimen; 3D surface shot o Transmission EM (TEM) – focus beam of electrons thru a specimen; cross section Microscopy Factors o Magnification – ratio of object’s image size to real size o Resolution – measure of clarity of image, or minimum distance of two distinguishable points o Contrast – visible differences in parts of sample Cell Types Prokaryotes o Domains (& Kingdoms) Bacteria & Archaea Eukaryotes o Domain Eukarya Kingdoms Protista, Fungi, Animalia, & Plantae All Cells o DNA – genetic code o Ribosomes – make proteins o Plasma membrane – layer surrounding cell o Cytoplasm – fluid region inside cell membrane Prokaryotic Cells o No nucleus DNA in region called nucleoid o No membrane-bound organelles o Cytoplasm everything inside plasma membrane Eukaryotic Cells o DNA in nucleus o Have membrane-bound organelles o Cytoplasm – region b/w plasma membrane & nucleus Cytosol – liquid outside organelles o Generally much larger than prokaryotic cells (1-5 vs 10-100 micrometer) Cell Parts Plasma Membrane o Selective barrier allowing passage of oxygen, nutrients, & waste o General structure – double layer of phospholipids Amphipathic – hydrophilic head & hydrophobic tail Nucleus o Has most of cell’s genes & usually most visible organelle o Nuclear envelope – double membrane enclosing nucleus Separates it from cytoplasm Nuclear Pores – regulate what enters & leaves nucleus o Nuclear Lamina – structural protein that maintains shape of nucleus o Chromatin – DNA + histones Histone – proteins that aid in condensing of DNA Chromosomes – condensed chromatin Cellular Division o Diploid – two chromosome sets o Haploid – one chromosome set o Mitosis – one diploid cell divides into 2 diploid cells (everywhere) o Meiosis – one diploid cell divides into 4 haploid cells (gonads) Nucleolus o Located in nucleus; makes ribosomal RNA (rRNA) o Ribosome Formation Proteins from cytoplasm enter nucleus & combine w/ rRNA Forms small & large subunits Subunits leave thru nuclear pores, form ribosomes in cytoplasm Ribosomes o rRNA & protein; synthesize proteins Cytosol (free ribosomes) Proteins used in cytosolic (e.g. enzyme) Bound to outside of ER or nuclear envelope (bound ribosomes) Proteins used in membrane, inside organelles, or secreted Endomembrane System o Components attached or connected via transfer by vesicles o Consists of: Nuclear envelope, Endoplasmic reticulum, Golgi apparatus, Lysosomes, Vacuoles, Plasma membrane o Endoplasmic Reticulum Network of membranous tubules & sacs (cisternae) ER membrane is continuous w/ nuclear envelope Inside called ER lumen Two distinct types… Smooth ER (no ribosomes) o Synthesize lipids Steroids, phospholipids o Metabolize carbohydrates o Store calcium (muscle) o Detoxify poisons Liver – adds hydroxyl group to make more soluble Rough ER (ribosomes on surface) o Make/secrete glycoproteins Proteins covalently bonded to carbs (Insulin & glucagon) o Distributes transport vesicles o Membrane factory for cell Makes phospholipids o Golgi Apparatus Center of manufacturing, warehousing, sorting, & shipping Made of membranous sacs stacked together (cisternae) Modifies products of ER Manufactures some macromolecules Sort & package materials into transport vesicles Cis face – receiving Trans face – transporting o Lysosome Stomach of cell; membranous sac of hydrolytic enzymes (digestion) Enzymes made by rough ER, transferred & processed by golgi, shipped to lysosome Hydrolyze proteins, fats, polysaccharides, & nucleic acids Lysosome Digestion Phagocytosis – ‘cellular eating’; cell engulfs another cell or particle; forms food vacuole o Lysosome fuses w/ vacuole & digests it Autophagy – lysosome digests & recycles cell’s own organelles & macromolecules o Vacuoles Large membrane-bound vesicle; different functions in different cells Food vacuoles – made by phagocytosis (amoebas, WBCs) Contractile vacuoles – pump excess water out of cell; maintains nutrient & ion concentration (freshwater protists) Central Vacuoles Large vacuole in plant cells Hydrolysis in plants/fungi (both lack lysosomes) Stockpiles proteins, ions (K+ & Cl-) Waste dump site Can contain poisons for defense Pigment proteins attracting pollinators Energy Production: Mitochondria & Chloroplasts o Have double membrane o Contain own DNA to make proteins o Proteins made by free ribosomes & by ribosomes inside organelle o Endosymbiont Theory Early ancestor of eukaryotes engulfed a non-photosynthetic prokaryote forming a endosymbiotic relationship At a later time, photosynthetic prokaryote uptaken in similar way Endosymbiont Evidence Both organelles have: Their own round DNA Ribosomes smaller than eukaryotes (similar to prokaryotes) Self Replication (binary fission) o Chloroplast Has chlorophyll (green pigment), enzymes, & other molecules for photosynthesis Found in leaves & other green organs of plants & algae Thylakoids – membranous sacs (poker chips) Granum – stacks of thylakoids Stroma – internal fluid w/ chloroplast DNA, ribosomes, & enzymes Photosynthesis: 6 CO2 + 6 H20 + sunlight → C6H12O6 + 6 O2 o Mitochondria Have smooth outer membrane & inner membrane folded into cristae (surface area) Inner membrane creates two compartments: Mitochondrial matrix o Mitochondrial DNA, ribosomes, & enzymes to catalyze steps of cellular respiration (makes ATP) Intermembrane space Cristae – create large surface area for enzymes to make ATP Cellular Respiration Glucose to ATP C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP Cytoskeleton o Network of fibers in cytoplasm that help support cell & maintain shape o Organize cell’s structures & activities; anchors many organelles o Interact w/ motor proteins to produce motility o Inside cell, vesicles travel along ‘monorails’ made of cytoskeleton o Cytoskeleton Components Microtubules Thickest fiber; made of tubulin Cell motility (w/ dynein) Separates chromosomes in cell division Moves organelles Structural component Centrosome o AREA near nucleus that acts as a “MT-organizing center” MTs grow out from a centrosome near nucleus o 2 centrioles make up centrosome Structure made of 9 sets of MT triplets Cilia & Flagella o Hair & tail-like structures Flagella long; normally 1-2 Cilia short; normally many o MTs & Dynein control beating of cilia & flagella Beating patterns different Dynein – Motor Protein Dynein arms alternately grab, move, & release outer MTs o Powered by ATP Protein cross-links limit sliding Forces exerted by dynein arms cause MT doublets to curve = Bends cilium or flagellum Intermediate Filaments Middle-sized fibers Made of diff. types of keratin Support cell shape & fix organelles in place More permanent cytoskeleton fixtures than other two classes Microfilaments or Actin Filaments Thinnest fiber; solid rods Made of a twisted double chain of actin subunits Form network (cortex) just inside cell membrane; supports shape Cellular & muscle movement Muscle Movement o Actin works w/ myosin (motor protein) o Thousands of actin filaments lined up parallel to each other o Thick filaments of myosin interlock w/ thin actin fibers Actin-Myosin Elsewhere o Amoeboid movement o Cytoplasmic streaming – circular flow of cytoplasm in cells speeding up distribution of materials Extracellular Components Most cells synthesize & secrete materials outside of cell membrane Cell Wall o Cellulose fibers embedded in other polysaccharides & protein o Protects cell, maintains shape, & prevents excessive water uptake o Prokaryotes, fungi, & some protists also have cell walls Extracellular Matrix (ECM) o Glycoproteins bind to integrins (receptor protein) in plasma membrane GPs = Collagen, proteoglycans, fibronectin o Functions: support, adhesion, movement, regulation Intercellular Junctions o Neighboring cells adhere, interact, & communicate thru physical contact o Plasmodesmata Connect plant cells Cytosol can pass thru Water, small solutes, RNA, & protein o Animal Cell Junctions Gap junctions (communicating) – provide cytoplasmic channels b/w 2 cells Tight junctions – 2 cell membranes pressed together; prevent leakage of extracellular fluid Desmosomes (anchoring) – fasten cells together into strong sheets