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A Tour of the Cell

A Tour of the Cell. Chapter 6 Introduction Bozeman Tutorial: Tour of the Cell (14:16). Overview of Cells. Cell Theory – Several statements assembled in the 1800’s to explain cells: a. All living things are made of cells. b. Cells are alike in structure and function.

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A Tour of the Cell

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  1. A Tour of the Cell Chapter 6 Introduction Bozeman Tutorial: Tour of the Cell (14:16)

  2. Overview of Cells • Cell Theory – Several statements assembled in the 1800’s to explain cells: • a. All living things are made of cells. • b. Cells are alike in structure and function. • c. Cells are the basic unit of life. • d. New cells come from pre-existing cells • Two reasons that cells are small: • a. Efficiency: Smaller cells have increased surface area to volume. If the cell is too big, it’s difficult to move nutrients/wastes across the membrane and throughout the cell. • b. Specialization: Having numerous small cells permits cells to have different functions.

  3. Two Types of Cells • 1. EUKARYOTIC – Kingdoms Animalia, Plantae, Fungi, Protista. • Eukaryotes contain a membrane-bound nucleus and other structures, called organelles, that have specific functions. The organelles are found in a jelly-like medium called cytosol. • Plant cells have three more organelles than the animal cells (cell wall, chloroplasts, and a large central vacuole). • 2. PROKARYOTIC – Kingdoms Archaebacteria and Eubacteria. • Prokaryotes are the simplest of all cells and were probably the first life forms, containing only cell wall, cell membrane, DNA, and ribosomes.

  4. Intercellular Junctions • Cells of a complex organisms are integrated into one functional organism. Cells interact through direct physical contact. • Cell walls of plants have perforations called plasmodesmata through which the living contents of adjacent cells are connected. • In animals there are three main types of junctions: tight junctions, desmosomes, and gap junctions.

  5. Tight Junctions • Membranes of neighboring cells are fused together forming a seal.

  6. Desmosomes • Cells are fastened together (spot weld) and reinforced with keratin filaments.

  7. Gap Junctions • Channels between cells provide for chemical communication.

  8. Tight junction Tight junctions prevent fluid from moving across a layer of cells Fig. 6-32 0.5 µm Tight junction Intermediate filaments Desmosome Desmosome Gap junctions 1 µm Extracellular matrix Space between cells Gap junction Plasma membranes of adjacent cells 0.1 µm

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