7-Cytoskeleton & Cell Motility PDF

CYTOSKELETON & CELL MOTILITY Presented by Jericho Parami  01 Objectives Describe the structure and function of the major cytoskeletal components: microtubules, intermediate filaments, and microfilaments. 02...

CYTOSKELETON & CELL MOTILITY Presented by Jericho Parami  01 Objectives Describe the structure and function of the major cytoskeletal components: microtubules, intermediate filaments, and microfilaments. 02 Explain the roles of motor proteins, such as kinesins and dyneins, in cellular transport and movement. 02 Understand how the cytoskeleton contributes to cellular motility and division through processes like cell crawling and mitotic spindle formation. CYTOSKELETON The cytoskeleton is a cellular framework made up of protein filaments that helps maintain the cell's structure, organizes the internal components, and enables various types of cellular movement, including cell division and intracellular transport (Alberts et al., 2014; Kratz, 2020). Alberts, B., Johnson, A., Lewis, J., Morgan, D., Raff, M., Roberts, K., & Walter, P. (2014). Molecular biology of the cell (6th ed.). Garland Science. Kratz, R. (2020). Molecular and cell biology for dummies (2nd ed.). Wiley. CYTOSKELETON MICROTUBULES Structure: Microtubules are hollow tubes made of alpha- and beta-tubulin proteins. They exhibit polarity: Plus end: Rapid growth. Minus end: Anchored at the Microtubule-Organizing Center (MTOC). CYTOSKELETON MICROTUBULES Funtions: Maintain cell shape and structure. Act as tracks for intracellular transport of vesicles and organelles. Form the mitotic spindle during cell division for chromosome segregation. CYTOSKELETON MOTOR PROTEINS KINESINS Move cargo toward the plus end of microtubules (toward the cell periphery). Transport vesicles and organelles, such as during synaptic transmission in neurons. DYNEINS Move cargo toward the minus end (toward the cell center). Involved in organelle positioning and retrograde transport. Drive the movement of cilia and flagella. CYTOSKELETON Microtubule-Organizing Centers (MTOCs) MTOCs nucleate and anchor microtubules within the cell. The centrosome is the primary MTOC in animal cells. Located near the nucleus. Consists of two centrioles. Directs microtubule growth, especially important during cell division (formation of spindle fibers). CYTOSKELETON Structure and Function of Cilia and Flagella Cilia and flagella are hair-like structures involved in cell movement or fluid movement across cell surfaces. Axoneme structure: 9+2 arrangement of microtubules: 9 doublets surrounding 2 central microtubules. CYTOSKELETON Structure and Function of Cilia and Flagella Function: Cilia: Short and numerous, move fluids (e.g., mucus in respiratory tracts). Flagella: Longer, usually singular, propel cells (e.g., sperm cells). Movement is driven by dynein, causing microtubule doublets to slide and create a bending motion. CYTOSKELETON INTERMEDIATE FILAMENTS Structure: Provide mechanical strength and resist tensile stress. Made of different proteins depending on cell type: Keratin in epithelial cells. Vimentin in connective tissue. Function: Maintain cell structure and stabilize organelles. Help cells withstand mechanical stress (important in muscle, skin, etc.). CYTOSKELETON MICROFILAMENTS (Actin Filaments) Structure: Helical filaments of actin monomers. Highly dynamic, continuously polymerizing and depolymerizing. Function: Provide mechanical support to the cell membrane. Play a key role in cell motility through the formation of lamellipodia and filopodia. Involved in cytokinesis during cell division by forming the contractile ring. Enable muscle contraction through interactions with myosin motor proteins. CYTOSKELETON CELLULAR MOTILITY Actin-based motility (Cell Crawling): Actin filaments push the plasma membrane forward to form: Lamellipodia: Sheet-like protrusions. Filopodia: Thin, spike-like projections. Actin and myosin interaction generates contractile forces to pull the cell body forward. CYTOSKELETON CELLULAR MOTILITY Microtubule-based motility: Microtubules and motor proteins (dynein and kinesin) facilitate movement inside cells (vesicle transport, organelle positioning). Microtubules in cilia and flagella enable cell movement (e.g., sperm motility). CYTOSKELETON CELLULAR MOTILITY Cell Division: Microtubules form the spindle apparatus during mitosis to ensure proper chromosome separation. IS THERE ANY QUESTIONS? Thank you for Listening! Alberts, B., Johnson, A., Lewis, J., Morgan, D., Raff, M., Roberts, K., & Walter, P. (2014). Molecular biology of the cell (6th ed.). Garland Science. Kratz, R. (2020). Molecular and cell biology for dummies (2nd ed.). Wiley.