Cell-to-cell interactions Flashcards
What are the 3 basic features in multicellular animals?
- Formation of diverse kinds of tissue
- Cells being able to communicate w/ each other
- Cells having markers of individual identity
What kind of proteins do the 3 basic features involve?
-Membrane proteins & proteins secreted by cells
What are the 7 kinds of connections between cells?
- Surface markers
- Septate junctions & tight junctions
- Desmosome (adhesive junction)
- Adherens junction (adhesive junction)
- Hemidesmosome/ focal adhesion (adhesive junction)
- Gap Junction (communicating junction/ Animals)
- Plasmodesmata (communicating junction/ Plants)
What are the 3 types of Adhesive Junctions?
- Desmosomes
- Adherens Junction
- Heridesmosome/ Focal adhesion
What are the 2 types of Communicating Junctions?
- Gap junction
- Plasmodesmata
What functions to mark the surfaces of cells?
-A key set of genes
When cells of the same tissue recognize each other, what do they do?
-They respond by forming connections between their surfaces to better coordinate their functions
What are Glycolipids?
- They’re surface markers for tissue-specific cells
- They’re lipids w/ carbohydrate heads
What blood types are the Glycolipids on the surface of RBD responsible for?
-A,B, and O blood types
What is an example of the function of the cell-surface markers?
-The recognition of “self” & “non-self” by the immune system= vital for multicellular organisms to defend themselves against invaders
What is Major Histocompatibility Complex (MHC)?
-Proteins= makers that vertebrates use to distinguish self from non-self
What is vital for a tissue to maintain its characteristic architecture?
-Cell junctions
What are Adhesive Junctions & where are they found?
- They mechanically attach the cytoskeleton of a cell with the cytoskeleton of other cells or to the extracellular matrix
- They’re found in tissues subject to mechanical stress= muscle & skin epithelium
What are Adherens Junctions & where are they found?
- They’re based on the protein Cadherin
- They’re found in animals ranging from jellyfish to vertebrates
What is Cadherin & how does it help adherens junctions?
- A protein that is Ca2+ dependent adhesion molecule w/ very wide phlyogenetic distribution
- It’s a single-pass transmembrane protein w/ extracellular domain of a cadherin in an adjacent cell to join cells together
How does Cadherin interact on the cytoplasmic side?
-They interact indirectly through other proteins w/ actin to form flexible connections between cells
What are Desmosomes?
- They are a cadherin-based junction unique to vertebrates
- They join adjacent cells= support tissues against mechanical stress
What 2 types of Cadherin do desmosomes have & what do they do?
-Desmocollin & Desmoglein= interact w/ intermediate filaments of cytoskeletons INSTEAD of actin
What are Hemidesmosomes & Focal adhesions?
- They connect cells to the basil lamina or other ECM
- Also connect the cytoskeleton of cells= actin filaments at focal adhesions & intermediate filaments at hemidesmosomes
What are the proteins that interact w/ the ECM in hemidesmosomes & focal adhesions?
-Integrins= Cell-surface receptors that bind to a protein component of the ECM
What are Septate Junctions?
-They’re found in both invertebrates & vertebrates & form a barrier that can seal off a sheet of cells
What are Tight Junctions?
- They’re unique to vertebrates & contain proteins called Claudins= abilty to occulde/block subtances from passing between cells
- IS A BRICK WALL
What are Communicating Junctions?
- Allow communication between cells by diffusion though small openings
- They permit small molcules or ions to pass from one cell to another
What are Gap Junctions?
- They’re found in both invertebrates & vertebrates (in invertebrates they’re formed by protein pannexins while the vertebrates= connexons)
- Provide passageways large enough to permit small substances (amino acids, simple sugars) to pass from one cell to the next but small enough to prevent passage from bigger molecules (proteins)
How do Gap Junctions form?
-When the pannexins/ connexons of 2 cells align perfectly= creates open channel that spans the membrane between the cells
What are Gap Junction channels?
- They’re dynamic structures that can open or close in response to a variety of factors (Ca2+ &H+ ions)
- Prevents damage from spreading by closing when Ca2+ tries to flow in due to the plasma membrane becoming leaky
What are Plasmodesmata?
- They function like gap junctions but they are for Plant cells & w/ a more complex structure
- They’re cytoplasmic connections that form across the touching plasma membranes of adjacent cells
- They’re lined w/ plasma membrane & contain a central tubule that connects the endoplasmic reticulum to the 2 cells
