Kate Rowe, Kylina John, Jacqueline Enriquez

1. Extracellular Components and Connections Between Cells Help Coordinate Cellular Activities Kate Rowe, Kylina John, Jacqueline Enriquez

2. Content: • Cell Walls of Plants • Intercellular Junctions of Plant Cells • ECM of Animal Cells • Intercellular Junctions of Animal Cells

3. How the cell wall helps coordinate cellular activity • Protects the plant cell • Maintains its shape • Prevents excessive uptake of water

4. Break Down of Cell Wall • Primary Cell Wall thin and flexible • Middle Lamella sticky, thin layer of pectins • Secondary Cell Wall strong durable matrix

5. Cell Walls of Plants Secondary Cell Wall Cell Membrane Primary Cell Wall Middle Lamella

6. Intercellular Junctions in Plants Plasmodesmata: channels in which plant cell walls are perforated with. Functions of plasmodesmata include: -Allowing cytosol to pass through, which connects cells to unify plant into one living thing. -Water and small solutes pass from cell to cell. -Macromolecules pass through and are transported on cytoskeleton.

7. Plasmodesmata in Plant Cells

8. What is the extracellular matrix (ECM)? • Something that is made by virtually all multi-cellular organisms. • Elaborate covering outside animal cell membranes, occupying the space between cells. It is composed of: • Collagen, proteoglycans, and fibronectin, which the cell secretes. • Different from the plant extracellular matrix, which is composed of cellulose. • Many ECM components are involved in cell-to-cell interactions.

9. Components of the ECM • Collagen • Most abundant glycoprotein (about half of the total protein in the body). • Forms strong fibers outside of the cell. • Fibers are embedded in a network made of proteoglycans. • Proteoglycans • Collagen fibers are embedded in a network made from proteoglycans. • Are another class of glycoproteins that consists of a small core protein with many carbohydrate chains covalently attached. • Large complexes can form when hundreds of proteoglycans become non-covalently attached to a single long polysaccharide molecule.

10. Components (cont.) • Fibronectin • Glycoprotein that attaches the ECM to the cell itself. • Binds to cell surface receptors called integrins, which are built into the plasma membrane of the cell. • Integrins • Cell surface receptor that connects to fibronectin, which attaches to the ECM • Span the membrane and bind on their cytoplasmic side to associated proteins attached to microfilaments of the cytoskeleton. • Transmit’s changes between the ECM and the cytoskeleton – it integrates changes occurring outside and inside the cell.

11. Polysaccharide molecule Proteoglycan complex Collagen EXTRACELLULAR FLUID Carbo- hydrates Fibronectin Core protein Integrins Proteoglycan molecule Plasma membrane Proteoglycan complex CYTOPLASM Micro- filaments Fig. 6-30

12. ECM Effect on Behavior • By communicating with a cell through integrins, the ECM can regulate a cell’s behavior. • ECM can influence the activity of genes in the nucleus. • Speculated that information probably reaches the nucleus by a combination of chemical and mechanical signaling pathways. • Mechanical includes fibronectin, integrins, and microfilaments of the cytoskeleton. • The cytoskeleton may then trigger chemical signaling pathways inside the cell, leading to changes in the proteins being made by the cell and therefore in its function. • The ECM may help coordinate the behavior of all the cells within that tissue. • Direct connections (intercellular junctions) between cells also function in this coordination.

13. Intercellular Junctions in Animal Cells • Tight Junctions: Specific proteins bind cell membranes which are pressed against each other. • Function: Tight Junctions prevent extracellular fluid from leaking across epithelial cells.

14. Intercellular Junctions in Animal Cells • Desmonsomes: also known as “anchoring junctions,” desmonsomes are like rivets that fasten cells together. • Desmonsomes are anchored to the cytoplasm by filaments made of keratin proteins.

15. Intercellular Junctions in Animal Cells • Gap Junctions: also known as “communicating junctions,” gap junctions act as cytoplasmic channels between cells. • Function: Each pore is surrounded by membrane proteins which allow ions, sugars, amino acids, and other things cells need to pass from cell to cell.

16. Intercellular Junctions in Animal Cells