Biology: How Life Works Active Lecture Slides Chapter 10 PDF

Morris Hartl Knoll Lue Michael Heitz Hens Lozovsky Merrill Phillis Pires Liu Biology: How Life Works Active Lecture Slides Chapter 10 Cell and Tissue Form Copyright © Macmillan Learning  Chapter 10 Cell and Tissue Architecture ...

Morris Hartl Knoll Lue Michael Heitz Hens Lozovsky Merrill Phillis Pires Liu Biology: How Life Works Active Lecture Slides Chapter 10 Cell and Tissue Form Copyright © Macmillan Learning  Chapter 10 Cell and Tissue Architecture  Tissues and Organs A tissue is a collection of cells that work together to perform a specific function. Two or more tissues combine and function together to make up an organ. The shape of cells and organs reflects their function. The cytoskeleton, cell junctions, and the extracellular matrix all contribute to the shape of cells, the integrity of tissues and organs, and the function of tissues and organs as integral units in the body. Exploring the Structure and Function of Skin The skin provides an excellent example of how cell structure and connections affect its function. The epidermis is a water-resistant and protective barrier formed by multiple layers of cells. The dermis supports the epidermis physically and supplies it with nutrients.  The Epidermis Cells arranged in more than one layer are called epithelial cells and make up epithelial tissue. Epithelial tissue covers the outside of the body and lines many internal structures of the body. The epithelial cells of the epidermis have melanocytes that give skin its color and keratinocytes that protect the underlying tissue. The basal lamina supports the epithelial cells. The Dermis The role of the dermis is to support the epidermis. The dermis contains a large amount of extracellular matrix, making up the connective tissue of the dermis layer. The main cell type found in the dermis is fibroblast, which produces the extracellular matrix and is important in repairing skin damage.  Cytoskeleton The cytoskeleton provides internal structural support and enables movement of substances within the cell. The cytoskeleton is formed from long chains of protein subunits joined together. Structure and Function of Microtubules Tubulin dimers aggregate to form a microtubule. A tubulin dimer is made up of one α and one β tubulin subunit. Microtubules radiate out from the centrosome, helping the cell to maintain its shape. Many organelles are tethered to microtubules. What would happen in a cell if its gene for α tubulin was mutated, so it was unable to bind to β tubulin? A. The cell would have no microtubules. B. The cell would have no microfilaments. C. The cell would be unaffected. D. The cell would have no intermediate filaments.  Microfilaments Microfilaments are the thinnest of the cytoskeletal structures. They are extremely branched and found just below the cell membrane. Microfilaments help reinforce and organize the proteins associated with the cell membrane. Epithelial Cells and Microfilaments Additional Functions of the Microfilaments Microfilaments take part in: 1. transport of materials inside cells. 2. shortening of muscle cells during contraction. 3. separation of daughter cells at the end of animal cell division.  Microtubules and Microfilaments Are Dynamic Microtubule and microfilament growth occurs more quickly at the plus ends. Microtubules are positioned with the minus ends near the centrosome and plus ends projecting toward the cell membrane. Microtubules are important for cell division and can go through rapid cycles of shortening followed by slower growth. Dynamic Instability Motor Proteins Contribute to Movement Within the Cell Here we see the movement of a vesicle on a microtubule track. An example of a microtubule track is the movement of a vesicle from the Golgi apparatus to the cell membrane. Kinesin moves cargo toward the plus end. Dynein moves cargo toward the minus end.  Kinesin and Dynein at Work The color changes in some cells are influenced by the concentration of pigment granules along microtubules, which is driven by the motor proteins kinesin and dynein. Microtubule Examples: Cilia and Flagella What would happen to a cell that depends on motile cilia for movement but lacks actin? A. The cell would not be able to move because dynein and kinesin could not function. B. The cell would not be able to move. C. The cell might be able to move if it used myosin to change shape. D. Nothing; motile cilia contain microtubules, not microfilaments. Intermediate Filaments Intermediate filaments provide mechanical strength to the cell. Intermediate filaments are made up of different proteins depending on the cell type. epithelial cells—keratins fibroblasts—vimentins neurons—neurofilaments nucleus—lamins Intermediate Filament Defects: Epidermolysis Bullosa  Major Functions of Cytoskeletal Elements Cell Adhesion: Sponge  Cell Adhesion: Amphibian Embryo  Cell Adhesion: Cadherins Cadherins are transmembrane proteins that bind adjacent cells, providing structural continuity between two cells. The Role of Integrins Integrins provide a way for cells to attach to the extracellular matrix. The cytoplasmic domain interacts with the extracellular matrix. The association is important for structural integrity of tissues under physical stress. Cell Junctions Cell junctions connect cells to other cells or to the basal lamina and are reinforced by the cytoskeleton. There are five types of cell junctions: 1. adherens junctions 2. desmosomes 3. hemidesmosomes 4. tight junctions 5. gap junctions Adherens Junctions Desmosomes Hemidesmosomes Tight Junctions Which adhesion molecule is particularly good at attaching the cell to the basement membrane? A. actin B. cadherin C. myosin D. integrin Which type of cell junction prevents the movement of substances through the space between cells? A. desmosomes B. adherens junctions C. tight junctions D. hemidesmosomes E. gap junctions  Clicker Question: Scenario (1 of 2) Suppose there is a mutation in a laminin-binding integrin gene that causes a loss of function in the cytoplasmic domains of the integrin. Which one of the outcomes would you expect to observe as a result of this mutation? A. The integrin would adhere to laminin, and the cytoplasmic domain would adhere to microtubules instead of microfilaments. B. The integrin would function normally because the cytoplasmic domain is not responsible for binding to laminin. C. The strength of tissues would decrease because the integrin could no longer associate with microfilaments.  Gap Junctions and Plasmodesmata Plasmodesmata—Plant Cell Plasmodesmata are connections between two plant cells that cross the cell wall and membrane. Gap junctions allow two cells to communicate through joined rings of integral membrane proteins. Plasmodesmata are communication channels that can cross the cell wall of plant cells because the cell membranes of the plants are continuous.  Interactions in Junctions, Adhesion Molecules, and Cytoskeletal Elements Extracellular Matrix Plant Extracellular Matrix Layers of the Cell Wall Animal Extracellular Matrix  Clicker Question: Scenario (2 of 2) The dermis of mammalian skin, including that of humans, contains a large amount of extracellular matrix proteins, including collagen and elastin. As a person ages, the amount of elastin in the dermis declines. Which of the following cell types is likely to be the cause of this change in the dermis of the skin? A. fibroblasts B. keratinocytes C. melanocytes D. epidermal cells Collagen Basal Lamina The basal lamina provides support for epithelial tissues. Collagen in the basal lamina provides flexibility to the tissue and scaffolding for other proteins to associate with it. The Extracellular Matrix and Cancer Cancer is metastatic when tumor cells escape the tumor and, through the circulatory system, move to another spot on the body. All blood vessels have a basal lamina, so in order for metastasis to occur, a tumor cell must cross the basal lamina of a blood vessel twice. Metastasis and Integrins All cells attach to the basal lamina through integrins. Researchers have identified a specific integrin that is found on metastatic cells but not on non-tumor cells. When these integrins are blocked, metastatic cells are unable to cross the basal lamina and move into the bloodstream.  The Extracellular Matrix’s Influence on Cell Shape The surface where cells grow and are able to attach has a significant effect on cell shape.  The Composition of the Extracellular Matrix and Cell Shape Having the appropriate proteins present in the extracellular matrix is important because protein type has a direct effect on cell shape. When laminins are added to cell growth cultures, neurons exhibit their appropriate shape. The Extracellular Matrix Influences Gene Expression Joan Caron examined the role of different proteins and the expression of albumin by hepatocytes grown in culture. Hepatocytes grown in the presence of only type I collagen did not express albumin. Hepatocytes grown in a mixture of extracellular matrix proteins and type I collagen showed increased albumin expression.  How Do We Know? Caron’s Experiments In a follow-up experiment, Caron grew hepatocytes with isolated single proteins and combinations of proteins from the extracellular matrix. The results showed that the extracellular matrix protein laminin influences the expression of albumin in hepatocytes.