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Biology 207 Spring 2004 Lecture 2: Cells Reading: R-Campbell Chapter 7 or chapter on cell structure from any introductory biology textbook Outline: 1. 2. 3. 4. 5. 6. Plasma Membrane Nucleus Cytoplasm Mitochondria Cytoskeleton Extracellular matrix/cell junctions Lecture: To understand what goes wrong in a cancer cell, we need to know more about the structure and function of normal cells. In today's class we will review some basic cell biology and point out some of changes that occur in cancer cells. [Insert schematic diagram of a cell] 1. Plasma membrane forms boundary of cell critical for receiving signals from outside cell and deciding what enters cell phospholipid bilayer contains embedded proteins, such as receptors Normal cell Let nutrients and oxygen in, wastes out Receive/send signals to other cells Cancer cell Same as normal cell Incorrectly process signals/send wrong signals Signals are sent and received by a cell usually via receptor proteins in the plasma membrane. [diagram of receptor] 2. Nucleus [diagram of cell illustrating structures in the nucleus] 1 nucleus=membrane bound organelle that contains the genetic material. Changes in appearance when cell divides. Normal cell Nucleus contains genes Nucleus directs cell to make proteins DNARNA protein Nucleus receives chemical signals from cytoplasm that alter gene expression Cancer cell Some of the genes are "mutated" Mutated genes in the nucleus direct synthesis of altered proteins Cancer cell nucleus receives the wrong signals; tell cell to divide or to turn on inappropriate genes Genes=segments of DNA that contain information to make RNA or proteins Mutation=change in the base sequence of DNA ACG TGC ACG TGA normal gene mutated gene Change DNA sequence change code for protein 3. Cytoplasm Consists of fluid (cytosol), proteins, ribosomes (sites of protein synthesis), and membrane bound organelles Organelles include Mitochondria: Energy metabolism Endoplasmic reticulum and Golgi body: Protein processing Lysosomes: Degration of organelles and proteins 4. Mitochondria mitochondria=organelles involved in energy metabolism and cell death Normal cell Efficiently make ATP, the energy storing molecule Old cells receive a signal to die so they are replaced by new cells Cancer cell Hog ATP and starve out normal cells Old cells not told to die; get too many cells cancer 5. Cytoskeleton cytoskeleton=Network of fibers throughout the cytoplasm Made of filamentous proteins: tubulin, actin, keratin Provide structural support Determine cell shape 2 Involved in cell movement Anchor cell-cell connections Move organelles around Move chromosomes during cell division Normal cell Predetermined cell shape Cancer cell Become metastatic, able to change shape and migrate from original site Cell division not regulated Divide in response to normal signals 6. Extracellular matrix/cell junctions ECM=material outside cell that holds cell in place yet allows for movement of nutrients, oxygen, and signaling molecules. Includes a lot of "sticky proteins" (collagen, proteoglycan, fibronectin). [diagram of cells adhering to basement membrane via ECM] Normal cell Cells stay put Cells anchored to ECM Cancer cell Cells migrate away Secrete enzymes that break down ECM Intercellular junctions Hold cells together Some allow communication between cells Some prevent fluid from seeping into tissues Most common in epithelia [diagram showing examples of cell junctions] Normal cell Cells attached to each other Cell communication good Cancer cell Cells lose their attachments Cell communication reduced 3
