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A Tour of the Cell

A Tour of the Cell. Chapter 6. Overview: The Importance of Cells. All organisms are made of cells Cells are the basic unit of structure and function in a cell Cells come from the reproduction of preexisting cells. Microscopy. Scientists use microscopes to

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A Tour of the Cell

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  1. A Tour of the Cell Chapter 6

  2. Overview: The Importance of Cells • All organisms are made of cells • Cells are the basic unit of structure and function in a cell • Cells come from the reproduction of preexisting cells

  3. Microscopy • Scientists use microscopes to visualize cells that are to small to see with the naked eye. • Light Microscopes (LMs) - pass visible light through a specimen - magnify cellular structures with lenses

  4. Electron Microscopes • Focus a beam of electrons through a specimen or onto its surface. • Two types: 1. scanning electron microscope (SEM) 2. transmission electron microscope (TEM)

  5. Scanning Electron Microscope (SEM) • Provides for detailed study of the surface of a specimen.

  6. Transmission Electron Microscope (TEM) • Provides for detailed study of the internal ultrastructure of cells.

  7. Cell Fractionation • Takes cells apart and separates the major organelles from one another. • Done with the use of a centrifuge

  8. Two Types of Cells: • Two types of cells make up every organism 1. prokaryotic 2. eukaryotic • What do they have in common: - bounded by a plasma membrane - contain a semifluid substance called the cytosol - contain chromosomes - contain ribosomes

  9. Prokaryotic Cells: - do not contain a nucleus - have their DNA located in a region called the nucleoid • Eukaryotic Cells: - contain a true nucleus - contain membrane-bound organelles - generally quite a bit larger than prokaryotic cells

  10. Prokaryotic Cells

  11. Cell Size • The logistics of carrying out cellular metabolism sets limits on the size of cells • A smaller cell has a higher surface to volume ratio, which facilitates the exchange of materials into and out of the cell.

  12. The Plasma Membrane • Functions as a selective barrier • Allows sufficient passage of nutrients and waste

  13. Panoramic View of the Eukaryotic Cell • Eukaryotic cells have extensive and elaborately arranged internal membranes, which form organelles. • Plant and animal cells have most of the same organelles.

  14. The Nucleus • Contains most of the genes in the eukaryotic cell • The nuclear envelope encloses the nucleus, separating its contents from the cytoplasm. • The nucleolus synthesizes ribosomal RNA and small ribosomal subunits

  15. Ribosomes • Particles made of ribosomal RNA and protein • The site of protein synthesiswhere the translation of the genetic instructions yields specific polypeptides. • Free ribosomes (cytosol) and bound ribosomes (rough ER)

  16. Endoplasmic Reticulum (ER) • Accounts for more than half the total membrane in many eukaryotic cells. • The ER membrane is continuous with the nuclear envelope • There are two distinct regions of ER: - Smooth ER (lacks ribosomes) - Rough ER (contains ribosomes)

  17. Functions of Smooth ER • Synthesizes lipids • Metabolizes carbohydrates • Stores calcium • Detoxifies poison

  18. Functions of Rough ER • Compartmentalize the cell • Produces proteins and membranes, which are distributed by transport vesicles. • Plays a role in intracellular transport

  19. The Golgi Apparatus • Receives many of the transport vesicles produced in the rough ER • Consists of flattened membranous sacs called cisternae • Functions: - synthesis and packaging of materials - production of lysososmes

  20. Golgi Apparatus

  21. Lysosomes • Membrane-enclosed sacs that contain hydrolytic enzymes • Hydrolytic enzymes are important in: - intracellular digestion - recycling of the cell’s organic materials - programmed cell death (apoptosis)

  22. Vacuoles • Membrane-bound sac that plays a role in: - intracellular digestion - release of cellular waste products • In plants, a large vacuole serves many functions: - storage of pigments/poisonous substances - role in cell growth - allows for a large surface area to volume ratio

  23. Mitochondria • Sites of cellular respiration • Structure: - double membrane that allows compartmentalization - outer membrane is smooth - inner membrane folded into cristae - cristae increase surface area for ATP production

  24. Mitochondria

  25. Chloroplasts • Found only in algae and higher plants • Site of photosynthesis • Contain chlorophylls: - responsible for green color - key light trapping molecules - predominantly chlorophyll a

  26. Chloroplasts • Structure: - thylakoids (membranous sacs) - stroma (internal fluid)

  27. Cytoskeleton • A network of fibers extending throughout the cytoplasm. • Function: - gives mechanical support to the cell and maintains its shape - provides anchorage for many organelles - involved in cell motility, which utilize motor proteins

  28. Cell Wall of Plants • An extracellular structure of plant cells that distinguishes them from animal cells • Made of cellulose fibers embedded in other polysaccharides and protein • Function: - protection - maintains its shape - prevents excess water uptake

  29. The Cell – A living unit greater than the sum of its parts • Cells rely on the integration of structures and organelles in order to function.

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