The extracellular

matrixECM

The area between

cells

The ECM of animal cells

• Animals cells lack the structure and support that a cell wall provides

• Have an ECM instead that provides some of the same support

Components of the ECM

• Cells secrete glycoproteins – This is the main

component of the ECM

All 3 of these are common ECM glycoproteins

• Collagen is the most common glycoprotein in the ECM

• Proteoglycans (a glycoprotein) form a woven network outside cells

• Collagen are like strong fibers that run throughout this network

• Cells are attached to the ECM by another glycoprotein: fibronectin

• On one side, fibronectin is attached to proteins in the plasma membrane

• On the other side, the fibronectin is attached to the glycoproteins of the ECM

Quick Think

Explain the role of:

•Fibronectins

•Collagen fibers

•Proteoglycans

in the extracellular matrix

The ECM allows for cell to cell communication

Intercellular junctions

• Cells in plants and animals are organized into tissues, organs, and organ systems

• Cells in a tissue may adhere to each other

The Plasmodesmata of plants

• Cells walls of plants are perforated with small channels called plasmodesmata

• Cytosol passes through the channel, thereby connecting the two cells

• Water, solutes, even proteins and RNA can move between cells

• Allows plant cells to function as a unified system, rather than isolated cells

Intercellular Junctions in Animal Cells

• 3 main types of junctions between animal cells

• These junctions are most common in epithelial tissue (skin, linings of organs, etc)

Tight junctions in animal cells

• The plasma membranes of neighboring cells are very tightly pressed together and bound by proteins

• Forms a seal or barrier around a group of cells

Desmosomes or anchoring junctions in animal cells

• Like rivets that fasten cells together in strong sheets

• Keratin filaments anchor these attachments in the cytoplasm

Gap junctions (or communicating junctions) in animal cells

• Similar to plasmodesmata in plant cells

• Provides a channel between cells that cytosol can travel through

• Allows for cell to cell communication– Important in cardiac

tissue and embryonic tissue

Quick Think:

Summarize the role and location of each of the 3 types of intercellular junctions