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BIO301: Cell Biology

Unit 4: The Plant Cell Wall and the Extracellular Matrix (ECM)   Different types of cells produce and secrete different molecules that can alter their external environment. An environment that has been altered in this way in the plant cell is the plant cell wall. It determines the cell shape and prevents cells from bursting because of osmotic pressure. An environment that has been altered in this way in animal cells is known as the extracellular matrix (ECM). The matrix’s main purpose is to form an ordered network for physical support, but it also plays a role in signaling, immunity, and wound healing. There are five main classes of ECM molecules; all ECMs are composed of some combination of these five types.

Unit 4 Time Advisory
Completing this unit will take you approximately 8 hours.

☐    Subunit 4.1: 1 hour

☐    Subunit 4.2–4.3: 2 hours

☐    Subunit 4.4: 4 hours

☐    Assessment: 1 hour

Unit4 Learning Outcomes
Upon completion of this unit, you will be able to - describe the composition and function of the plant cell wall; - describe ECM molecules, including their functions and where each type of molecule is most common; - describe the functions of different kinds of adhesion molecules; and - distinguish between types of intercellular junctions.

4.1 The Plant Cell Wall   - Reading: NCBI Bookshelf: Cooper’s “Cell Walls and the Extracellular Matrix” Link: NCBI Bookshelf: Cooper’s Cell Walls and the Extracellular Matrix (HTML)

 Instructions: Read the subsection “Plant Cell Walls” along with
associated figures (Figs. 12.46, 12.47, 12.48, 12.49, and 12.50).  

 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.

4.2 The Extracellular Matrix (ECM)   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “Cell Walls and the Extracellular Matrix” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: Cell Walls and the Extracellular Matrix (HTML)
 
Instructions: Read the subsection “The Extracellular Matrix,” along with all associated figures (Figs. 12.51–12.61). This reading covers the topics outlined in subunits 4.2, 4.3, and all inclusive subunits.

 Reading this text and taking notes should take approximately 2
hours.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

4.2.1 Collagen   This subunit is covered by the reading assigned beneath subunit 4.2. Focus on figures 12.52–12.55 and table 12.2.

4.2.2 Elastic Fibers   This subunit is covered by the reading assigned beneath subunit 4.2. Focus on the subsection “The Extracellular Matrix” section (paragraph 6).

4.2.3 Proteoglycans   This subunit is covered by the reading assigned beneath subunit 4.2. Focus on figure 12.57.

4.2.4 Hyaluronan   This subunit is covered by the reading assigned beneath subunit 4.2. Focus on figure 12.57.

4.2.5 Adhesive Glycoproteins   This subunit is covered by the reading assigned beneath subunit 4.2. Focus on the subsection “the Extracellular Matrix” (paragraphs 10 and 11) with associated figures (Figs. 12.58 and 12.59).

4.3 Basal Lamina   This subunit is covered by the reading assigned beneath subunit 4.2. Focus on figure 12.51.

4.4 Cellular Adhesion   - Reading: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: “Cell-Cell Interactions” Link: National Center for Biotechnology Information’s Bookshelf: Sinauer Associates, Inc.: Professor Geoffrey Cooper’s The Cell: A Molecular Approach, 2e: Cell-Cell Interactions (HTML)
 
Instructions: Read the introduction and the subsections “Cell Adhesion Proteins,” “Tight Junctions,” and “Gap Junctions” and click on all associated figures and tables (Figs. 12.62–12.66 and Table 12.3). These will cover the material in 4.4–4.5.

 Reading this text and taking notes should take approximately 2
hours.  
    
 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 “Cell Adhesion, Motility, and Division” Link: University of California, Berkeley: Professor David G. Drubin’s Cell Adhesion, Motility, and Division (YouTube)

    Also available in: iTunes U
     
    Instructions: Scroll down to item 22 titled Lecture 21: “Cell Adhesion, Motility, and Division,” and select “View in iTunes.” This lecture covers subunits 4.4, 4.5, and all inclusive subunits.

    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.

4.4.1 Cell Adhesion Molecules (CAMs)   This subunit is covered by the reading and video assigned beneath subunit 4.3. Focus on the “Cell Adhesion Proteins” section and figures 12.62–12.64 and table 12.3.

4.4.2 Immunoglobulin CAM (Ig-CAM)   This subunit is covered by the reading and video assigned beneath subunit 4.4. Focus on the “Cell Adhesion Proteins” section.

4.4.3 Cadherin Family   This subunit is covered by the reading and video assigned beneath subunit 4.4. Focus on the “Cell Adhesion Proteins” section and figure 12.64.

4.4.4 Integrin Family   This subunit is covered by the reading and video assigned beneath subunit 4.4. Focus on the “Cell Adhesion Proteins” section.

4.4.5 Selectin Family   This subunit is covered by the reading and video assigned beneath subunit 4.4. Focus on the “Cell Adhesion Proteins” section.

4.5 ntercellular Junctions   4.5.1 Tight Junctions   This subunit is covered by the reading and video assigned beneath subunit 4.4. Focus on the “Tight Junctions” section and figure 12.65.

4.5.2 Gap Junctions   This subunit is covered by the reading and video assigned beneath subunit 4.4. Focus on the “Gap Junctions” section and figure 12.66.

4.5.3 Adherens Junctions and Desmosomes   This subunit is covered by the reading and video assigned beneath subunit 4.4. Focus on the “Cell Adhesion Proteins” section.

4.5.4 Plasmodesmata   This subunit is covered by the reading assigned beneath subunit 4.4.  Focus on the “Plant Cell Adhesion and Plasmodesmata” section.

4.6 ECM and Connective Tissue   4.6.1 Loose Connective Tissue (LCT)   This subunit is covered by the reading and video assigned beneath subunit 4.1. Focus on the “The Extracellular Matrix” section. There are substantial differences between loose and dense connective tissue. Dense tissue is largely composed of collagen (type I), while loose connective tissue has as equal amounts of elastic fibers and collagen. DCT makes up ligaments and tendons, while LCT surrounds nearly every internal organ in the body.

4.6.2 Dense Connective Tissue (DCT)   Dense connective tissue consists of extracellular matrix in which fibers and cells are embedded. Type I collagen is the predominant component of the fibers. There are considerably few cells in this tissue. Dense connective tissue is quite strong.
 
There are two types of dense connective tissue based on the arrangement of fibers. In dense regular connective tissue, the fibers are in a common direction or parallel to one another. In rows between the fibers are fibroblasts, cells that produce the collagen and extracellular matrix. Dense regular connective tissue withstands pulling along the axis of the fibers and is found in tendons that connect muscle to bone and ligaments that connect bone to bone. Dense irregular connective tissue contains type I collagen fibers in bundles without any specific orientation. This tissue type is found in the body where pulling forces are exerted in various directions. This tissue often occurs in sheets, such as in the dermis of the skin or the pericardium of the heart.

  • Assessment: The Saylor Foundation’s “Unit 4 Quiz” Link: The Saylor Foundation’s “Unit 4 Quiz” (HTML)
     
    Instructions: Complete this quiz after working through Unit 4. The questions are either multiple choice or matching. 

    Completing this assessment should take approximately 1 hour.