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What are cells? How many types are there? How Cells Are Put Together?

What are cells? How many types are there? How Cells Are Put Together?. Chapter 4 We shall cover the first part today and the rest next time. What is a Cell. It is the…. Smallest unit of life Can survive on its own (or can do so if it has to) Is highly organized for metabolism

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What are cells? How many types are there? How Cells Are Put Together?

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  1. What are cells?How many types are there?How Cells Are Put Together? Chapter 4 We shall cover the first part today and the rest next time

  2. What is a Cell • It is the…. • Smallest unit of life • Can survive on its own (or can do so if it has to) • Is highly organized for metabolism • Senses and responds to environment • Has potential to reproduce

  3. Structure of Cells All start out life with: • Plasma membrane • Region where DNA is kept • Cytoplasm • Two types of cells exist: • Prokaryotic • Eukaryotic

  4. Why Are Cells So Small? Cells absorb stuff across their membranes… • Surface-to-volume ratio • The bigger a cell is, the less surface area there is per unit volume • Above a certain size, material cannot be moved in or out of cell fast enough

  5. Remember Elephants • Why don’t we see 90 foot high elephants. It would be better for them. • They would need ears as big as sail ship sails to cool themselves based on their lack of surface area…

  6. Surface-to-Volume Ratio

  7. Early Discoveries • Mid 1600s - Robert Hooke observed and described cells in cork • Late 1600s - Antony van Leeuwenhoek observed sperm, microorganisms

  8. Cell Theory 1) Every organism is composed of one or more cells 2) Cell is smallest unit having properties of life - therefore viruses are not considered living 3) Continuity of life arises from growth and division of single cells - we are all related to the very first life forms on this Planet

  9. Tools of Biology - Microscopes • Create detailed images of something that is otherwise too small to see • Light microscopes • Simple or compound • Electron microscopes • Transmission EM or Scanning EM

  10. Limitations of Light Microscopy • Wavelengths of light are 400-750 nm • If a structure is less than one-half of a wavelength long, it will not be visible • Light microscopes can resolve objects down to about 200 nm in size

  11. Tools - Electron Microscopy • Uses streams of accelerated electrons rather than light • Electrons are focused by magnets rather than glass lenses • Can resolve structures down to 0.5 nm

  12. Electron Microscope incoming electron beam condenser lens (focuses a beam of electrons onto specimen) specimen objective lens intermediate lens projector lens viewing screen (or photographic film)

  13. The cells skin - The Lipid Bilayer • Main component of cell membranes • Gives the membrane its fluid properties • Two layers of phospholipids

  14. Fluid Mosaic Model • Membrane is a mosaic of • Phospholipids • Glycolipids • Sterols • Proteins • Most phospholipids and some proteins can drift through membrane • MOVIE link above

  15. Membrane Proteins • Adhesion proteins - GLUES • Communication proteins - INFO • Receptor proteins - INBOUND • Recognition proteins

  16. Continue…How are cells put together? Watch me please!

  17. Prokaryotic Cells • Include just Archaea and eubacteria • DNA is not enclosed in nucleus • DNA is not enclosed in nucleus • DNA is not enclosed in nucleus • DNA is not enclosed in nucleus • Generally the smallest, simplest cells • No organelles

  18. Prokaryotic Structure bacterial flagellum pilus plasma membrane bacterial flagellum Most prokaryotic cells have a cell wall outside the plasma membrane, and many have a thick, jellylike capsule around the wall. cytoplasm, with ribosomes DNA in nucleoid region

  19. Eukaryotic Cells • Have a nucleus and other organelles • Eukaryotic organisms • Plants • Animals • Protistans • Fungi

  20. WHY HAVE AN NUCLEUS?Functions of Nucleus • Keeps the DNA molecules of eukaryotic cells separated from metabolic machinery of cytoplasm • Makes it easier to organize DNA and to copy it before parent cells divide into daughter cells

  21. Nuclear Envelope • Two outer membranes (lipid bilayers) • Innermost surface has DNA attachment sites • Pores span bilayer one of two lipid bilayers (facing nucleoplasm) NUCLEAR ENVELOPE nuclear pore (protein complex that spans both lipid bilayers) one of two lipid bilayers (facing nucleoplasm)

  22. SEE IT! http://video.search.yahoo.com/video/play?vid=1079578458&vw=g&b=0&pos=1&p=endomembrane+system&fr=yfp-t-501

  23. Canals inside cellsEndoplasmic Reticulum (ER) • Group of related organelles in which lipids are assembled and new polypeptide chains are modified • Products are sorted and shipped to various destinations • POST OFFICE OF THE CELL

  24. Components of Endomembrane System Endoplasmic reticulum Golgi bodies Vesicles

  25. Endoplasmic Reticulum • In animal cells, continuous with nuclear membrane • Extends throughout cytoplasm • Two regions: rough and smooth

  26. Rough ER • Arranged into flattened sacs • Ribosomes on surface give it a rough appearance • Some polypeptide chains enter rough ER and are modified • Cells that specialize in secreting proteins have lots of rough ER

  27. Smooth ER • A series of interconnected tubules • No ribosomes on surface • Lipids assembled inside tubules • Smooth ER of liver inactivates wastes, drugs • Sarcoplasmic reticulum of muscle is a specialized form

  28. Golgi Bodies • Put finishing touches on proteins and lipids that arrive from ER • Package finished material for shipment to final destinations • Material arrives and leaves in vesicles

  29. Vesicles • Membranous sacs that move through the cytoplasm • Lysosomes • Peroxisomes

  30. Central Vacuole • Fluid-filled organelle • Stores amino acids, sugars, wastes • As cell grows, expansion of vacuole as a result of fluid pressure forces cell wall to expand • In mature cell, central vacuole takes up 50-90 percent of cell interior

  31. Mitochondria • ATP-producing powerhouses • Double-membrane system • Carry out the most efficient energy-releasing reactions • These reactions require oxygen • Similar to Ancient bacteria in chemistry

  32. Mitochondrial Structure • Outer membrane faces cytoplasm • Inner membrane folds back on itself • Membranes form two distinct compartments • ATP-making machinery is embedded in the inner mitochondrial membrane

  33. Chloroplasts Convert sunlight energy to ATP through photosynthesis

  34. Like Bacteria? • Both mitochondria and chloroplasts resemble bacteria • Have own DNA, RNA, and ribosomes

  35. Plant Cell Features

  36. Animal Cell Features

  37. Cytoskeleton • Present in all eukaryotic cells • Basis for cell shape and internal organization • Allows organelle movement within cells and, in some cases, cell motility

  38. Mechanisms of Movement • Length of microtubules or microfilaments can change • Parallel rows of microtubules or microfilaments actively slide in a specific direction • Microtubules or microfilaments can shunt organelles to different parts of cell

  39. Cell Wall Plasma membrane • Structural component that wraps around the plasma membrane • Occurs in plants, some fungi, some protistans Primary cell wall of a young plant

  40. Plant Cell Walls Secondary cell wall (3 layers) Primary cell wall

  41. Plant Cuticle • Cell secretions and waxes accumulate at plant cell surface • Semi-transparent • Restricts water loss

  42. Matrixes between Animal Cells • Animal cells have no cell walls • Some are surrounded by a matrix of cell secretions and other material

  43. Cell Junctions - [molecular staples] • Plants • Plasmodesmata • Animals • Tight junctions • Adhering junctions • Gap junctions plasmodesma

  44. Animal Cell Junctions

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