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Cytology: the Study of the Structure and Function of Cells

Cytology: the Study of the Structure and Function of Cells. LO Covered: B1. A Bit of History. Cell research began in the 17 th century 3 researchers are credited with developing the cell theory: Schleiden&Schwann: all living things are composed of cells

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Cytology: the Study of the Structure and Function of Cells

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  1. Cytology: the Study of the Structure and Function of Cells LO Covered: B1

  2. A Bit of History • Cell research began in the 17th century • 3 researchers are credited with developing the cell theory: • Schleiden&Schwann: all living things are composed of cells • Virchow: all cells come from pre-existing cells

  3. Some Cell Terms & Basic Info • There are 2 basic types of cells • Prokaryotic: (no internal membranesno nucleus or membrane-bound organelles) • Eukaryotic: (nucleus & membrane-bound organelles) • Organelle: a distinct sub-cellular structure which carries out a specific function • Ultrastructure: the inner makeup of a cell

  4. Meet the Organelles.. 4 groups: • cell membrane • nucleus-related structures • endomembrane system organelles • energy-producing organelles

  5. The Cell Membrane We’ll focus on this later in the unit but why do all cells have a membrane? In our bodies cell membranes have 4 functions: • Act as a barrier to pathogens, toxins, etc. • To mark the cell as self • To act as a receptor for messages from other cells in the body • To allow things to be transported in and out of cell (Big Marty Rips Tops)

  6. All of These Functions Allow the Cell to Maintain Homeostasis Homeostasis is maintenance of a relatively constant internal environment …it’s one of the BIG concepts this year!!

  7. Associated With the Cell Membrane are some Vesicles and Vacuoles • Secretory Vesicles carry things out of the cell by fusing with the membrane so that their contents are released outside the cell (exocytosis) • Vesicles and Vacuoles are created by the cell membrane when it pinches in (endocytosis)

  8. The Nucleus-related Organelles& Structures • The Nucleus contains the cell’s chromosomes and therefore controls the cell’s ability to: • make proteins • undergo cell division • Related structures: nuclear envelope, nucleolus, nucleoplasm, chromosomes, chromatin, and ribosomes (all but ribosomes are part of the nucleus)

  9. Proteins: VIMs (Very Important Molecules!) • Many of the cells important structures are made from proteins • Enzymes which are needed for the cell to carry most cellular reactions necessary for life are also proteins • The type of proteins that your cells make determine who you are

  10. Chromosomes, Chromatin, Chromatids...Confusion! • When the cell is in its normal state (not dividing) the cell’s genetic information (encoded in DNA) is dispersed within the nucleuschromatin • When a cell is replicating (mitosis or meiosis) the chromatin condenses to form chromosomes • Each chromosome consists of 2 sister chromatids

  11. The Nucleolus: The Instructions for Making Ribosomes • Makes ribosomal RNA (rRNA) which is a building block of ribosomes • There may be more than one present (nucleoli) • Surrounded by semifluid medium: nucleoplasm

  12. The Nuclear Envelope • Surrounds the nucleus • Continuous with the ER • A double membrane • Has openings: nuclear pores to allow certain things in and out Function? Regulate entry/exit of materials Nuclear pore

  13. The Connection Between the Nucleus and Ribosomes • Nucleus is where the instructions for making proteins are located (genes) • Ribosomes actually synthesize (make) proteins • How do the instructions get from the nucleus to the ribosomes? • mRNA

  14. An Analogy ribosomes nucleus

  15. Cytoplasmic Free-floating in the cytoplasm, make proteins (such as enzymes) needed within the cell Endoplasmic Attached to endoplasmic reticulum When attached to ER the ER is called Rough ER (RER) Proteins made here are often secreted (e.g. a peptide hormone) There Are Two Types of Ribosomes

  16. Cytoplasmic ribosomes Endoplasmic ribosomes (RER)

  17. Ribosomes: a connection between prokaryotes and eukaryotes • Ribosomes are the smallest and most numerous organelle in the average eukaryotic cell. They differ from other organelles because they lack membranes • Bacteria also have ribosomes • Eukaryotic cells also have ribosomes within their mitochondria and chloroplasts

  18. Endomembrane System Organelles • There are 2 types of Endoplasmic Reticulum • Rough (has ribosomes attached to it) • Smooth (lacking ribosomes) • Associated with the ER are: • Transition or transport vesicles • the Golgi Apparatus (Bodies) • Lysosomes • All of these organelles compartmentalize the cell so that chemical rxns take place only in certain areas

  19. Rough ER Continuous with the nuclear envelope Studded with ribosomes Proteins that are made by these ribosomes are processed, modified and transported within the lumen of the RER Protein may pass on to the SER for packing into vesicles (See figure 3.5c p53) Smooth ER Continuous with the RER Lacks attached ribosomes There are various functions assoc .with the SER: Synthesis of lipids(fats) membrane phospholipids steroid hormones (e.g.. Testosterone) Detoxification of drugs in liver Forms vesicles to transport ER products to GA or PM RER Vs. SER

  20. Golgi Apparatus: processing, packaging, secretion • A stack of curved saccules • Receives protein or lipid-filled vesicles from ER • GA modifies the contents of the vesicles (e.g. adds sugar groups or makes a protein’s toxin active) • Vesicles leave GA for plasma membrane (secretion) others become lysosomes

  21. Lysosomes: Prepare to Die Mr. Bond • The cell’s poison pill: • Contains digestive (hydrolytic) enzymes • Involved in autodigestion: • Digest old organelles • Allows cell to commit suicide if infected with a virus • Programmed cell death (e.g.. tadpole’s tale) • Produced by the GA • Digestion of food in single-celled organisms (intracellular digestion) • Killing of bacteria by WBCs involves lysosomes

  22. http://www.cellsalive.com/mac.htm

  23. The Energy-related Organelles • Mitochondria and chloroplasts are both related to obtaining energy • Chloroplasts are only found in plant cells. They are the site of photosynthesis • Mitochondria are found in both plant and animal cells and make ATP—the cell’s main energy currency (how energy requiring processes are “paid” for by the cell)

  24. What’s Left? • Cytoplasm and Vacuoles • The cytoplasm is the site of many of the cell’s key biochemical rxns • It is semifluidbut cytoskeleton is located here • Plant cells have one large vacuole whereas animal cells have smaller and more numerous vacuoles • Vacuoles are storage areas for important substances (e.g.. In plantswater)

  25. Your Assignment: • Complete the Cell organelle chart and practice questions (all) • Read pages 56&57 and write a summary about the structure and functions of chloroplasts and mitochondria • Your summary should be: • Brief • Point form • Contain what you consider to be the essential information about these organelles

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