BIOL #09: Cell Communication (II) Flashcards
1
Q
How Do Adjacent Cells Connect and Communicate?
A
- Unicellular organisms do not usually connect to one another
+ physical connections between cells are the basis of multicellularity. - Cells of multicellular organisms adhere to one another and have specific, distinct structures and functions.
+ Groups of similar cells performing similar functions comprise tissues.
2
Q
Cell-Cell Attachments
A
- The structures that hold cells together vary among multicellular organisms.
- Cell-cell connections help adjacent cells adhere to each other.
- Cell-cell gaps allow adjacent cells to communicate with each other.
3
Q
Connections between Plant Cells
A
- Plant cells are glued together by the middle lamella, which is:
+ Composed of gelatinous pectins. - Pectins are polysaccharides.
+ Continuous with the adjacent plant cells’ primary cell walls.
4
Q
Connections between Animal Cells
A
- A middle-lamella-like layer exists between cells in many animal tissues.
+ made of gelatinous polysaccharides
+ polysaccharide glue may be reinforced by cable-like proteins (e.g. collagen) that span the ECM to connect adjacent cells. - In animal cells there are two main types of cell junctions that hold cells together: Tight junctions & Desmosomes
+ These junctions are especially common in epithelial tissue, which lines the external and internal surfaces of the body.
5
Q
Tight Junctions
A
- Tight junctions
+ composed of specialized proteins in the plasma membranes of adjacent animal cells. - proteins line up and bind to each other and form a watertight seal between the two plasma membranes.
- Tight junctions are usually found between cells in tissues that form a barrier, such as the tissue lining the stomach or bladder.
6
Q
Desmosomes
A
- Desmosomes are made of proteins that link the cytoskeletons of adjacent cells.
+ These proteins bind to each other and to the proteins that anchor cytoskeletal intermediate filaments. - Desmosomes are common in epithelial and muscle tissue.
7
Q
The Molecular Basis of Selective Adhesion
A
- Animal cells attach to each other selectively because there are several classes of cell adhesion proteins.
- Each major cell type has its own cell adhesion proteins.
- These cell-cell connections are also species and tissue specific.
8
Q
Cell Communication via Cell-Cell Gaps
A
- Direct connections between cells in the same tissue allow cells to communicate and work together in a coordinated fashion.
- Plant cells are connected by plasmodesmata.
- Cells in animal tissues are connected by gap junctions.
9
Q
Plasmodesmata
A
- Plant cell walls are perforated with plasmodesmata, membrane-lined channels filled with cytoplasm.
- Cytosol passes through the plasmodesmata, joining the internal environments of adjacent cells.
+ These connection unify most of a plant into a single, continuous living system - Water and small solutes can pass freely between cells.
10
Q
Gap Junctions
A
- Gap junctions provide cytoplasmic channels between adjacent animal cells similar to plasmodesmata of plants.
- Ions, sugars, amino acids and other small molecules can pass through gap junctions.
11
Q
Overview of Cell Signaling
A
- Signal transduction pathway
+ a series of steps by which a signal on a cell’s surface is converted into a specific cellular response
12
Q
Where Do Cell Signals Come From?
A
- The signals received by cells, whether originating from other cells or from changes in the physical environment, take various forms – including light and touch.
- Most cells communicate with each other via chemical signals.
13
Q
Evolution of Cell Signaling
A
- Pathway similarities between prokaryotes and eukaryotes:
+ suggest that ancestral signaling molecules evolved in prokaryotes.
+ modified later in single-celled and multicellular eukaryotes. - Conclusion: a shared evolutionary history of cell signaling mechanisms in prokaryotes and eukaryotes.
14
Q
Quorum Sensing in Bacteria
A
- Unicellular organisms live together and communicate with one another.
+ Cell-cell communication in bacteria is called quorum sensing. - Bacteria release species-specific signaling molecules when their numbers reach a specific threshold.
+ Quorum sensing allows bacteria populations to carry out activities that are only productive when performed by a critical mass of cells in synchrony
15
Q
Direct Contact
A
- One type of local signaling
- Cell junctions involve direct contact between the cytoplasm of cells
- Cell-cell recognition involves direct contact between membrane molecules