Ch. 4 Outline – Cell Structure & Function

1. Ch. 4 Outline – Cell Structure & Function

2. Cell Theory • A unifying concept in biology • States that: • All organisms are composed of cells • Matthais Schleiden in 1838 • Theodor Schwann in 1839 • All cells come only from preexisting cells • Rudolph Virchow in 1850’s • Smallest unit of life

3. Organisms and Cells

4. Sizes of Living Things

5. Cell Size • Most much smaller than one millimeter (mm) • Some as small as one micrometer (mm) • Size restricted by Surface/Volume (S/V) ratio • Surface is membrane, across which cell acquires nutrients and expels wastes • Volume is living cytoplasm, which demands nutrients and produces wastes • As cell grows, volume increases faster than surface • Cells specialized in absorption modified to greatly increase surface area per unit volume

6. Surface to Volume Ratio Total Surface Area 96 cm2 192 cm2 384 cm2 Total Volume 64 cm3 64 cm3 64 cm3 Surface Area Per Cube / Volume Per Cube 1.5 : 1 3 : 1 6 : 1

7. 1. Magnification a. How much larger the object appears compared to real size Microscopy Vocabulary

8. a. Measure of clarity of image b. Minimum distance two points can be separated and still be distinguished as two separate points 2. Resolving power   vs  

9. Microscopy Today:Compound Light Microscope • Light passed through specimen • Focused by glass lenses • Image formed on human retina • Max magnification about 1000X • Resolves objects separated by 0.2 mm, 500X better than human eye

10. Microscopy Today:Transmission Electron Microscope • Abbreviated T.E.M. • Electrons passed through specimen • Focused by magnetic lenses • Image formed on fluorescent screen • Similar to TV screen • Image is then photographed • Max magnification 1,000,000 X • Resolves objects separated by 0.00002 mm, 100,000X better than human eye

11. Microscopy Today:Scanning Electron Microscope • Abbreviated S.E.M. • Specimen sprayed with thin coat of metal • Electron beam scanned across surface of specimen • Metal emits secondary electrons • Emitted electrons focused by magnetic lenses • Image formed on fluorescent screen • Similar to TV screen • Image is then photographed

12. Microscopy Today:Immunofluorescence Light Microscope • Antibodies developed against a specific protein • Fluorescent dye molecule attached to antibody molecules • Specimen exposed to fluorescent antibodies • Ultra-violet light (black light) passed through specimen • Fluorescent dye glows in color where antigen is located • Emitted light is focused by glass lenses • Allows mapping distribution of a specific protein in cell

13. Microscopy Today:Confocal Microscopy • Narrow laser beam scanned across transparent specimen • Beam is focused at a very thin plane • Allows microscopist to optically section a specimen • Sections made at different levels • Allows assembly of 3D image on computer screen that can be rotated

14. Microscopy Today:Video-enhanced Contrast Microscopy • Great for specimens with low contrast, like living cells • Image is captured by TV camera instead of eye • Image is then “tweaked” by adjusting contrast • Darkest part of image is made black • Lightest part of image is made white • All parts in between made shades of gray • Also allows various shades to be converted to different colors for more contrast

15. Microscopy Today:Phase Contrast Microscopy • Great for transparent specimens with low contrast, like living cells • Some organelles have higher density than others • Speed of light is affected by density • Light passes more slowly through high density than low density • Light waves entering a specimen “in phase” exit some parts of the specimen out of phase • Microscope shows only light that is slower or faster • Causes transparent organelles to “glow”

16. Microscopy and Amoeba proteus

17. Microscopy and Cheek Cells

18. Prokaryotic Cells:Domains • Lack a membrane-bound nucleus • Structurally simple • Two domains: • Bacteria • Three Shapes • Bacillus (rod) • Coccus (spherical) • Spirilla (spiral) • Archaea • Live in extreme habitats

19. Shapes of Bacterial Cells

20. Prokaryotic Cells: Visual Summary

21. Prokaryotic Cells:The Envelope • Cell Envelopes • Glycocalyx • Layer of polysaccharides outside cell wall • May be slimy and easily removed, or • Well organized and resistant to removal (capsule) • Cell wall • Plasma membrane • Like in eukaryotes • Form internal pouches (mesosomes)

22. Prokaryotic Cells:Cytoplasm & Appendages • Cytoplasm • Semifluid solution • Bounded by plasma membrane • Contains inclusion bodies – Stored granules of various substances • Appendages • Flagella – Provide motility • Fimbriae – small, bristle-like fibers that sprout from the cell surface • Sex pili – rigid tubular structures used to pass DNA from cell to cell

23. Eukaryotic Cells • Domain Eukarya • Protists • Fungi • Plants • Animals • Cells contain: • Membrane-bound nucleus • Specialized organelles • Plasma membrane

24. Eukaryotic Cells :Organelles • Compartmentalization: • Allows eukaryotic cells to be larger than prokaryotic cells • Isolates reactions from others • Two classes: • Endomembrane system: • Organelles that communicate with one another • via membrane channels • Via small vesicles • Energy related organelles • Mitochondria & chloroplasts • Basically independent & self-sufficient

25. Plasma Membrane

26. Hypothesized Origin of Eukaryotic CellsEndosymbiosis

27. Cell Fractionation, andDifferential Centrifugation • Cell fractionation is the breaking apart of cellular components • Differential centrifugation: • Allows separation of cell parts • Separated out by size & density • Works like spin cycle of washer • The faster the machine spins, the smaller the parts that settled out

28. Cell Fractionation, andDifferential Centrifugation Grindcells Figure 4C Thencentrifugelonger@ 15,000 g Thencentrifugeeven longer@ 100,000 g Centrifuge@ 600 g Sedimentcontainsnuclei Sedimentcontainsmitochondria,lysosomes Sedimentcontainsribosomes,ER Solubleportion ofcytoplasm.Nosediment

29. Animal Cell Anatomy

30. Plant Cell Anatomy

31. Nucleus • Command center of cell, usually near center • Separated from cytoplasm by nuclear envelope • Consists of double layer of membrane • Nuclear pores permit exchange between nucleoplasm & cytoplasm • Contains chromatin in semifluid nucleoplasm • Chromatin contains DNA of genes • Condenses to form chromosomes • Dark nucleolus composed of rRNA • Produces subunits of ribosomes

32. Anatomy of the Nucleus

33. Ribosomes • Serve in protein synthesis • Composed of rRNA • Consists of a largesubunit and a smallsubunit • Subunits made in nucleolus • May be located: • On the endoplasmic reticulum (thereby making it “rough”), or • Free in the cytoplasm, either singly or in groups called polyribosomes

34. Nucleus, Ribosomes, & ER Figure 4.9

35. Endomembrane System • Restrict enzymatic reactions to specific compartments within cell • Consists of: • Nuclear envelope • Membranes of endoplasmic reticulum • Golgi apparatus • Vesicles • Several types • Transport materials between organelles of system

36. Endomembrane System: A Visual Summary

37. Endomembrane System:The Endoplasmic Reticulum • Rough ER • Studded with ribosomes on cytoplasmic side • Protein anabolism • Synthesizes proteins • Modifies proteins • Adds sugar to protein • Results in glycoproteins • Smooth ER • No ribosomes • Synthesis of lipids

38. Endoplasmic Reticulum

39. Endomembrane System:The Golgi Apparatus • Golgi Apparatus • Consists of 3-20 flattened, curved saccules • Resembles stack of hollow pancakes • Modifies proteins and lipids • Packages them in vesicles • Receives vesicles from ER on cis face • Prepares for “shipment” in vesicles from trans face • Within cell • Export from cell (secretion, exocytosis)

40. Golgi Apparatus

41. Endomembrane System:Lysosomes • Membrane-bound vesicles (not in plants) • Produced by the Golgi apparatus • Low pH • Contain lytic enzymes • Digestion of large molecules • Recycling of cellular resources • Apoptosis (programmed cell death, like tadpole losing tail) • Some genetic diseases • Caused by defect in lysosomal enzyme • Lysosomal storage diseases (Tay-Sachs)

42. Lysosomes

43. Peroxisomes • Similar to lysosomes • Membrane-bounded vesicles • Enclose enzymes • However • Enzymes synthesized by free ribosomes in cytoplasm (instead of ER) • Active in lipid metabolism • Catalyze reactions that produce hydrogen peroxide H2O2 • Toxic • Broken down to water & O2 by catalase

44. Peroxisomes

45. Vacuoles • Membranous sacs that are larger than vesicles • Store materials that occur in excess • Others very specialized (contractile vacuole) • Plants cells typically have a central vacuole • Up to 90% volume of some cells • Functions in: • Storage of water, nutrients, pigments, and waste products • Development of turgor pressure • Some functions performed by lysosomes in other eukaryotes

46. Vacuoles

47. Endomembrane System: A Visual Summary

48. Energy-Related Organelles:Chloroplast Structure • Bounded by double membrane • Inner membrane not folded • Disc-like thylakoids are stacked to formgrana • Suspended in semi-fluid stroma • Green due to chlorophyll • Green photosynthetic pigment • Found ONLY in membranes of thylakoids of chloroplast

49. Energy-Related Organelles:Chloroplasts • Captures light energy to drive cellular machinery • Photosynthesis • Synthesizes carbohydrates from CO2 & H2O • Makes own food using CO2 as only carbon source • Energy-poor compounds converted to energy rich compounds

50. Energy-Related Organelles:Chloroplast Structure