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Cell Structure & Function

Cell Structure & Function. Microscope History. Hooke’s (1665) drawings of cork. Early light microscope. Electron microscope. Microscopic Images. Paramecium. Light Micrograph. Scanning Electron Micrograph. Transmission Electron Micrograph. Scanning Electron Micrograph. Cell Theory.

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Cell Structure & Function

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  1. Cell Structure & Function

  2. Microscope History Hooke’s (1665) drawings of cork Early light microscope Electron microscope

  3. Microscopic Images Paramecium LightMicrograph Scanning Electron Micrograph Transmission Electron Micrograph Scanning Electron Micrograph

  4. Cell Theory • All living things are composed of one or more cells • Cells are: • Basic unit of structure • Basic unit of function • All cells come from preexisting cells

  5. Basic Cell Structure • All cells possess a plasma membrane, cytoplasm, genetic material • Plasma membrane has phospholipid bilayer, embedded glycoproteins • Isolates cytoplasm from environment • Regulates molecular movement into and out of cell • Interacts with other cells/environment

  6. Amoeba

  7. Relative Sizes Unaided eye Light Microscope ElectronMicroscope SpecialE.M. 100 m Eukaryotic Cells 10 m 1 m 10 cm 1 cm 1 mm Virus 100 m 10 m Proteins 1 m 100 nm Atoms 10 nm 1 nm 0.1 nm

  8. Cell Types • Prokaryotic: • Smaller, 1—5 µm • No organelles • No nucleus • DNA in circular loop • Eukaryotic: • Larger, 8—100 µm • Membranous organelles • Nucleus • DNA in linear chromosomes

  9. Generalized Prokaryote Nucleoid DNA Plasmid DNA Cytosol Flagellum Capsule PlasmaMembrane Cell Wall

  10. Bacilli (1000x)

  11. Eukaryotic Cells • Genetic material - DNA, found in the nucleus • Cytoplasm – everything else within the plasma membrane • Cytosol (the fluid part) • Water • Salts • Organic monomers and polymers • Organelles

  12. Generalized Cell AnimalCell Chloroplasts Centrioles Mitochondria Golgi Nucleus EndoplasmicReticulum PlantCell

  13. Generalized Cell AnimalCell Nucleolus Ribosomes Central Vacuole PlantCell Smooth E.R. Cell Wall

  14. Control Structuresa. Nucleus • a. Nucleus • Structure: • about 5 mm in diameter • bound within the nuclear envelope • contains DNA complex (chromatin) • Function: • genes within DNA include instructions for production of proteins to control metabolism and other cell functions

  15. The Nucleus Nucleolus Pores Chromatin Threads(Chromosomes) NuclearEnvelope

  16. Chromosomes Nucleus Chromosomes Nucleoli Cell Wall

  17. Control Structures b. Nuclear Envelope • Structure: • double membrane (two bilipid layers) • nuclear lamina (protein network) • between membrane layers (20-40 nm) • perforated by pores (100 nm diameter) • Function: • stabilizes shape • part of endomembrane system (transport)

  18. Control Structuresc. Nucleolus • Structure: • spherical region in nucleus • composed of RNA • Function: • packages ribosome subunits

  19. Control Structuresd. Ribosomes • Structure: • complexes of RNA and proteins • composed of two subunits • Function: (as either free or bound) • free ribososmes make proteins that function in the cytoplasm • bound (to ER) ribosomes make proteins destined for membranes or for export

  20. Ribosomes

  21. 2. Endomembrane Systema. ER (Endoplasmic Reticulum) • Structure: • continuous with outer membrane of nuclear envelope • folded membrane network • Function: (as either smooth or rough) • rough ER (studded with ribosomes) makes proteins and membranes (grow in place) • smooth ER makes lipids, phospholipids, and steroids

  22. Rough vs. Smooth ER: TEM Ribosomes Smooth ER Rough ER

  23. The Endoplasmic Reticulum UnitMembrane Ribosomes Vesiclesforming

  24. 2. Endomembrane System b. Golgi Apparatus • Structure: • stack of flattened membrane sacs • two faces • cis “receiving” • trans “shipping” • Function: • receives molecules from ER for processing • molecules are modified and packaged as they are passed from sac to sac

  25. The Golgi Complex Material ReceivedFrom ER Material Destinedfor Export TEM

  26. 2. Endomembrane System c. Lysosomes • Structure: • Small membrane sacs made by Golgi • Vesicles contain hydrolytic enzymes • Function: • Digest material engulfed by cell • Digest and recycle damaged organelles

  27. 2. Endomembrane System d. Central Vacuoles • Structure: • Large, water-filled spaces (cell sap) • Can take up over 90% of cell volume • Enclosed by tonoplast (single membrane) • Function: • Storage of pigments (red/blue), acids, salts, wastes • Maintain cell pressure (turgor pressure)

  28. Plant Wilting &the Central Vacuole NormalPlant Cell In SaltWater Normal Cytoplasm In Salt Water Vacuole(tonoplast) Space between Cell Walland Cell Membrane Cell Wall

  29. 2. Endomembrane System e. Contractile Vacuole • Structure: • Membrane-bounded sac • Connected to canals radiating through cytoplasm • Function: • Control water balance in hypotonic environment. • Fills with water entering cytoplasm (due to osmosis). • Pumps water out of the cell by contracting • Requires ATP

  30. Contractile Vacuoles Expandedwith Water Paramecium sp. 1 2 Expelling Waterto Outside

  31. The Endomembrane System Food Vacuole Vessicle forExport Lysosome Golgi EndoplasmicReticulum Vessicle

  32. 3. Other Membranous Organelles a. Plastids • a group of plant and algal membrane-bound organelles • Chromoplasts (chromo = color) • pigment containing plastids • fruits, flowers, autumn leaves • ii. Amyloplasts (amylo = starch) • colorless plastids that store starch • found in roots and tubers • Chloroplasts (chloro = green)

  33. The Amyloplast DoubleBilipidMembrane StarchGranules

  34. a. Plastids iii. Chloroplast • Structure: • Contain chlorophyll • Bounded by a double membrane • Thylakoid staked into grana • Stroma (viscous fluid) outside thylakoids • Contain ribosomes and some DNA • Function: • Site of Photosynthesis • Captures light energy • Produces carbohydrate from CO2 and H2O • Self-replicating (semi-autonomous)

  35. The Chloroplast Granum OuterMembrane Stroma Intermembrane Space Thylakoids

  36. Elodea (400x)

  37. 3. Other Membranous Organelles b. Mitochondria • Structure: • Bounded by double membrane • Inner membrane folded into cristae • Mitochondrial matrix – within cristae • Contain own DNA and ribosomes • Function: • Site of cellular respiration • convert energy stored in food into ATP • “powerhouse” of the cell • number varies, but related to cell’s metabolic activity • Self-replicating (semi-autonomous)

  38. The Mitochondrion OuterMembrane InnerMembrane Matrix Cristae

  39. 4. The Cytoskeleton • Protein fibers • Cell shape; networks of intermediate filaments • Cell movement; microfilaments & microtubules • Amoeboid movement • Muscle contraction • Cell migration during development • Organelle movement & suspension • Cyclosis; pathways for vesicle migration • Cell division

  40. The Cytoskeleton Actin monomers PlasmaMembrane Microfilaments IntermediateFilaments Mitochondrion Fibrous subunits Microtubule EndoplasmicReticulum Tubulin dimer

  41. 4. The Cytoskeleton a. Centrioles • Structure: • Pair of cylindrical structures • 9 sets of triplet microtubules • Arranged in a ring • ~ 50 nm at right angles • Function: • Replicate during cell division

  42. Centriole x.s. T.E.M.

  43. 4. The Cytoskeleton b. Cilia and Flagella • Structure: • Tubular extensions of plasma membrane • Anchored by basal body (like centriole) • “9+2” arrangement • 9 doublet microtubules in complex • 2 single microtubules in center • Function: • Movement of fluid, or locomotion • Cilia: numerous, paddle-like, synchronized • Flagella: longer, fewer, more whip-like

  44. Cilia & Flagella x.s. T.E.M. Shaft Paramecium CellMembrane Euglena Base(a Centriole)

  45. Flagellum Parts Shaft, l.s. Cell Membrane Shaft,x.s. Microtubule Doublets Dynein Arms Central Singlets Microtubule Triplets Basal Body,x.s. Basal Body

  46. Flagella Movement Water Water Corkscrew Movement(Pulls) Whipping Movement(Pushes) Scanning E.M.of sperm on egg

  47. Movement of Cilia Active Stroke Recovery Stroke Water Cilia on trachea surface

  48. 5. Surfaces and Junctionsa. Cell Wall • Structure: • Microfibrils of Cellulose in a Matrix • Primary Cell Wall • Thin, flexible • Secondary Cell Wall • Deposited in Laminated Layers • Middle Lamella • Sticky polysaccharides (pectins) • Function: • Protects and Maintains Shape • Holds Cells Together • Prevents Excess Water Intake

  49. The Cell Wall

  50. 5. Surfaces and Junctions b. Communication Structures Plasma membrane(edge view) Tight junctionsseal membranesto block transport Cells liningbladder Tight junctionsformed by strandsof protein Tight Junction Small intestine Plasma membrane(edge view) Protein filamentsin cytoplasm Cells liningsmall intestine Protein strandsrivet cells together, but permit passage of substances desmosome Desmosome

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