Tight junctions form a seal between plasma membranes of adjacent cells and create a barrier around groups of cells. Desmosomes anchor cells together strongly through keratin filaments. Gap junctions contain channels that allow cytosol and small molecules to pass between neighboring cells, enabling cell-to-cell communication important in tissues like the heart and embryos.

1. The
extracellular
matrix
ECM
The area
between
cells

2. 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

3. Components of the ECM
• Cells secrete
glycoproteins
– This is the main
component of the
ECM
All 3 of these
are common
ECM
glycoproteins

4. • Collagen is the most common glycoprotein
in the ECM

5. • Proteoglycans (a
glycoprotein) form
a woven network
outside cells
• Collagen are like
strong fibers that
run throughout
this network

6. • 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

7. Quick Think
Explain the role
of:
•Fibronectins
•Collagen fibers
•Proteoglycans
in the
extracellular
matrix

8. The ECM allows for cell to cell
communication

9. Intercellular junctions
• Cells in plants and animals are organized
into tissues, organs, and organ systems
• Cells in a tissue may adhere to each other

10. 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

11. • Water, solutes,
even proteins
and RNA can
move between
cells
• Allows plant
cells to function
as a unified
system, rather
than isolated
cells

13. 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)

15. 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

16. Desmosomes or anchoring
junctions in animal cells
• Like rivets that
fasten cells
together in strong
sheets
• Keratin filaments
anchor these
attachments in
the cytoplasm

17. 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

18. Quick Think:
Summarize the role and location of each of the 3
types of intercellular junctions