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BIO301: Cell Biology

Unit 5: The Cytoskeleton   The cytoskeleton, as the name suggests, provides the physical support for the interior of the cell. You might think of it as cellular skeleton. There are three main types of support molecules: actin, tubulin, and intermediate filaments. All the muscles fibers in your body are mainly composed of these support molecules. These molecules also build an internal highway within the cell, upon which almost everything is transported. This unit will explore all three molecules in detail and provide some important examples of what they combine to create.

Unit 5 Time Advisory
Completing this unit will take you approximately 21 hours.

☐    Subunit 5.1: 4.5 hours

☐    Subunit 5.2: 5 hours

☐    Subunit 5.3: 3 hours

☐    Subunit 5.4: 2 hours

☐    Subunit 5.5: 4 hours

☐    Assessment: 2.5 hour

Unit5 Learning Outcomes
Upon completion of this unit, you will be able to: - describe the different roles of actin, tubulin, and intermediate filaments; - describe the properties and functions of actin, tubulin, and intermediate filaments; - describe the means through which cytoskeletal molecules are formed; and - determine which cytoskeletal molecule or process has been disrupted when given an example of a particular cellular problem or lack of function.

  • Assessment: University of Arizona’s Biology Project: “Cell Biology” Link: University of Arizona’s Biology Project: Cell Biology (HTML)

    Instructions: In the “Cytoskeleton” tutorial, under “Test Yourself (5 problems)”, answer questions 1 and 3–5.

    Completing this assessment should take approximately 30 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

5.1 Cytoskeleton Molecules   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “The Cytoskeleton and Cell Movement” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: The Cytoskeleton and Cell Movement (HTML) 

 Instructions: Read the introduction. This will cover the material
in subunits 5.1.1–5.1.3.  

 Reading this text and taking notes should take approximately 1
hour.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.
  • Lecture: University of California, Berkeley: Professor David G. Drubin’s “Actin Filaments: Structural and Dynamic Properties” Link: University of California, Berkeley: Professor David G. Drubin’s Actin Filaments: Structural and Dynamic Properties (YouTube)

    Also available in: iTunes U
     
    Instructions: Scroll down the webpage to item 26 titled Lecture 17: “Actin Filaments: Structural and Dynamic Properties,” and click on “View in iTunes.” This lecture will also cover the topics outlined in subunits 5.1.1–5.1.3.

    Watching this lecture and taking notes should take approximately 2 hours.
     
    Terms of Use: This resource is released under a Creative Commons Attribution-NonCommercial-NoDerivs Works 3.0 Unported License. It is attributed to the University of California, Berkeley and the original version can be found here.

5.1.1 Actin   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “Structure and Organization of Actin Filaments” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: Structure and Organization of Actin Filaments (HTML)
 
Instructions: Read the introduction.

 Reading this text and taking notes should take approximately 30
minutes.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

5.1.2 Tubulin   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “Microtubules” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: Microtubules (HTML)
 
Instructions: Read the introduction and subsections “Structure, Assembly, and Dynamic Instability,” paragraph one along with associated figure (Fig. 11.37).

 Reading this text and taking notes should take approximately 30
minutes.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

5.1.3 Intermediate Filaments   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “Intermediate Filaments” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: Intermediate Filaments (HTML)
 
Instructions: Read the introduction and the subsection “Intermediate Filament Proteins,” along with Figure 11.31.

 Reading this text and taking notes should take approximately 30
minutes.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

5.2 Actin Family   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “Structure and Organization of Actin Filaments” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: Structure and Organization of Actin Filaments (HTML)
 
Instructions: Read the introduction and subsections “Assembly and Disassembly,” “Organization,” and “Association of Actin Filaments” along with all associated figures (Figs.11.2–11.14). These will cover the material in 5.2.1–5.2.5 and 5.5.1.

 Reading this text and taking notes should take approximately 1
hour.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.
  • Lecture: University of California, Berkeley: Professor Randy Schekman’s “Actin-Binding Proteins and Cell Migration” Link: University of California, Berkeley: Professor Randy Schekman’s Actin-Binding Proteins and Cell Migration (YouTube)

    Also available in: iTunes U
     
    Instructions: Scroll down the webpage to item 25 titled Lecture 18: “Actin Binding Proteins and Cell Migration,” and click on “View in iTunes.” This lecture also covers the topics outlined in subunit 5.5.1.

    Watching this lecture and taking notes should take approximately 2 hours.
     
    Terms of Use: This resource is released under a Creative Commons Attribution-NonCommercial-NoDerivs Works 3.0 Unported License. It is attributed to the University of California, Berkeley and the original version can be found here.

5.2.1 Actin Polymerization   This subunit is covered by the reading and video assigned beneath subunit 5.2. Focus on the “Assembly and Disassembly of Actin Filaments” section and Figures 11.2 and 11.3.

5.2.2 Actin Binding Proteins   This subunit is covered by the reading and video assigned beneath subunit 5.2. Focus on the “Assembly and Disassembly of Actin Filaments” section and Figure 11.5.

5.2.3 Actin Filament Capping Proteins   - Reading: National Center for Biotechnology Information’s Bookshelf: W.H. Freeman: H. Lodish, A. Berk, S.L. Zipursky, et al.’s Molecular Cell Biology: “Section 18.2: The Dynamics of Actin Assembly” The Saylor Foundation does not yet have materials for this portion of the course. If you are interested in contributing your content to fill this gap or aware of a resource that could be used here, please submit it here.

[Submit Materials](/contribute/)

5.2.4 Actin Filament Severing Proteins   - Reading: National Center for Biotechnology Information’s Bookshelf: W.H. Freeman: H. Lodish, A. Berk, S.L. Zipursky, et al.’s Molecular Cell Biology: “Section 18.2: The Dynamics of Actin Assembly” Link: National Center for Biotechnology Information’s Bookshelf: W.H. Freeman: H. Lodish, A. Berk, S.L. Zipursky, et al.’s Molecular Cell Biology: Section 18.2: The Dynamics of Actin Assembly

 Instructions: Scroll down the webpage, and read the section titled
“Some Proteins Control the Lengths of Actin Filaments by Severing
Them.”  

 Reading this text and watching the lecture should take
approximately 1 hour.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

5.2.5 Actin Filament Cross-Linking (or “Bundling”) Proteins   This subunit is covered by the reading and video assigned beneath subunit 5.2. Focus on the “Organization of Actin Filaments” section and Figure 11.6.

5.3 Tubulin   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “Microtubules” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: Microtubules (HTML)
 
Instructions: Read the introduction and subsections “Structure, Assembly, and Dynamic Instability” and “Stabilization of Microtubules,” along with all associated figures (Figs. 11.37, 11.38, and 11.44). These will cover the material in 5.3.1–5.3.3.

 Reading this text and taking notes should take approximately 1
hour.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.
  • Lecture: University of California, Berkeley: Professor David G. Drubin’s “Microtubules: Structure and Dynamic Properties” Link: University of California, Berkeley: Professor David G. Drubin’s Microtubules: Structure and Dynamic Properties (YouTube)
     
    Also available in: Tunes U
     
    Instructions: Scroll down the webpage to item 20 titled Lecture 23: “Microtubules: Structure and Dynamic Properties,” and click on “View in iTunes.”

    Watching this lecture and taking notes should take approximately 2 hours.
     
    Terms of Use: This resource is released under a Creative Commons Attribution-NonCommercial-NoDerivs Works 3.0 Unported License. It is attributed to the University of California, Berkeley and the original version can be found here.

5.3.1 Microtubule Assembly from GTP Tubulin   This subunit is covered by the reading and video assigned beneath subunit 5.3. Focus on the “Structure, Assembly, and Dynamic Instability of Microtubules” section and figure 11.38.

5.3.2 Microtubule Associated Proteins   This subunit is covered by the reading and video assigned beneath subunit 5.3. Focus on the “Stabilization of Microtubules and Cell Polarity” section.

5.3.3 Microtubule Destabilizing and Stabilizing Proteins   This subunit is covered by the reading and video assigned beneath subunit 5.3. Focus on the “Stabilization of Microtubules and Cell Polarity” section.

5.4 Intermediate Filaments   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “Intermediate Filaments” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: Intermediate Filaments (HTML)
 
Instructions: Read the introduction and the subsection “Intermediate Filament Proteins,” along with Figure 11.31. These will cover the material in 5.4.1–5.4.4.

 Reading this text and taking notes should take approximately 1
hour.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.
  • Lecture: University of California, Berkeley: Professor David G. Drubin’s “Intermediate Filaments and Septins” Link: University of California, Berkeley: Professor David G. Drubin’s Intermediate Filaments and Septins (YouTube)

    Also available in: iTunes U
     
    Instructions: Scroll down to item 21 titled Lecture 22: “Intermediate Filaments and Septins,” and click on “View in iTunes.”

    Watching this lecture and taking notes should take approximately 1 hour.
     
    Terms of Use: This resource is released under a Creative Commons Attribution-NonCommercial-NoDerivs Works 3.0 Unported License. It is attributed to the University of California, Berkeley and the original version can be found here.

5.4.1 Rod Domains   This subunit is covered by the reading and video assigned beneath subunit 5.4. Focus on the subsection “The Intermediate Filament Proteins.”

5.4.2 Lamins   This subunit is covered by the reading and video assigned beneath subunit 5.4. Focus on the subsection “The Intermediate Filament Proteins.”

5.4.3 Desmins   This subunit is covered by the reading and video assigned beneath subunit 5.4. Focus on the subsection “The Intermediate Filament Proteins.”

5.4.4 Keratins   This subunit is covered by the reading and video assigned beneath subunit 5.4. Focus on the subsection “The Intermediate Filament Proteins.”

5.5 Cytoskeletal Models   5.5.1 Treadmilling   This subunit is covered by the reading and video assigned beneath subunit 5.2. Focus on the “Assembly and Disassembly of Actin Filaments” section and Figure 11.4.Treadmilling is a process in which actin and tubulin units appear to be walking. This occurs when individual units fall off one end (the minus end) while units add to the other end (the plus end), resulting in a motion that resembles walking.

5.5.2 Filopodia and Lamellipodia   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “Actin, Myosin, and Cell Movement” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: Actin, Myosin, and Cell Movement (HTML)
 
Instructions: Read the subsection entitled “Cell Crawling.”

 Reading this text and taking notes should take approximately 1
hour.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

5.5.3 Desmosomes and Hemidesmosomes   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “Intermediate Filaments” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: Intermediate Filaments (HTML)
 
Instructions: Read the subsection “Intracellular Organization of Intermediate Filaments,” along with Figure 11.34.

 Reading this text and taking notes should take approximately 1
hour.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

5.5.4 Skeletal Muscle Filament   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “Actin, Myosin, and Cell Movement” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: Actin, Myosin, and Cell Movement (HTML)

 Instructions: Read the subsection entitled “Muscle Contraction.”  

 Reading this text and taking notes should take approximately 1
hour.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

5.5.5 Kinesin-Dynein   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “Microtubule Motors and Movements” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: Microtubule Motors and Movements (HTML)
 
Instructions: Read the introduction and subsections “Identification of Microtubule Motor Proteins,” “Organelle Transport,” and “Cilia and Flagella,” along with all associated figures (Figs. 11.45–11.46 and 11.51, and 11.53). These will cover the material in subsections 5.5.5–5.5.7.

 Reading this text and taking notes should take approximately 1
hour.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

5.5.6 Flagella   This subunit is covered by the reading assigned beneath subunit 5.5.5. Focus specifically on the “Cilia and Flagella” section of the reading.

5.5.7 Cilia   This subunit is covered by the reading assigned beneath subunit 5.5.5. Focus specifically on the “Cilia and Flagella” section of the reading.

  • Assessment: University of Arizona’s Biology Project: “Cell Biology” Link: University of Arizona’s Biology Project: Cell Biology (HTML)

    Instructions: In the “Cytoskeleton” tutorial, under “Test Yourself (5 problems),” answer questions 1 and 3–5.

    Completing this assessment should take approximately 1 hour.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Assessment: The Saylor Foundation's “Unit 5 Quiz” Link: The Saylor Foundation's Unit 5 Quiz (HTML)
     
    Instructions: Complete the linked quiz to test your knowledge of the material covered in Unit 5.

    Completing this assessment should take approximately 1 hour.