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Bio - Chapter 7 - Cell to Cell Interactions


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receptor proteins
-have a 3-dimensional shape that fits a specific signal molecule.
-when a signal molecule and a receptor protein bind, a change in the receptor protein is induced and a response is generated.
techniques for finding receptor proteins
1) immunochemistry
2) molecular genetics
types of cell signaling
1) direct contact
2) paracrine signaling
3) endocrine signaling
4) synaptic signaling
-autocrine signaling
autocrine signaling
when cells send signals to themselves, secreting signals that bind to specific receptors on their own plasma membranes.
direct contact
cell to cell is in close contact
paracrine signaling
signal molecules are released by a cell that diffuse through the extracellular fluid to other cells, but it short lived and localized.
endocrine signaling
signal molecules released by cells remain in extracellular fluid for a long time and travel wideley throughout body.
longer lived signal molecules used in endocrine signaling
synaptic signaling
intracellular communication that provides rapid communication using neurtransmitters, which move through a synaptic gap rather than through intracellular fluid.
signal molecules used in synaptic signaling
chemical synapse
association of a neuron and its target cell
intracellular receptors
receptors located within the cell and trigger a variety of activity
- ex:
act as gene regulators
act as enzymes
cell surface receptors
receptor proteins on the outer surface of the cell that convert the extracellular signal to an intracellular one.
-useful for water soluble signals that cannot diffuse through plasma membranes.
Types of cell surface receptors
1) Chemically Gated Ion Channels
2) Enzymic Receptors
3) G Protein Linked Receptors
chemically gated ion channels
open or close when signal molecules bind to the channel
enzyme receptors
usually activate intracellular proteins by phosphorylation
ion channel
pore in chemically gated ions channels which ions pass through
protein kinases
enzyme activated when a signal molecule binds to an enzyme receptor, it adds prosphate groups to proteins
G protein linked receptors
acts indirectly on enzymes or ion channels in the plasma membranes with the aid of an assisting protein, G protein (aka GTP)
G protein
assisting protein in G protein linked receptors
second messengers
relay messages from receptors to target proteins.

cAMP (found in all animal cells)
calcium ions (high outside cell and in ER, low in cytoplasm.
adenylyl cyclase
stimulated by G protein, produces large amounts of cAMP within the cell
highly specialized groups of cells (blood, muscle)
cell identity
cells contain an array of marker proteins located on the cell surface
tissue specific identity markers
glycolipids (tissue specific cell surface markers)
MHC proteins (self from nonself)
cell junctions
long lasting or permanent connections inbetween cells
types of cell junctions:
tight junctions
anchoring junctions
communication junctions
tight junctions
connect plasma membranes of adjacent cells in a sheet, preventing small molecules from leaking inbetween the cells
anchoring junctions
mechanically attach the cytoskeleton of a cell to the cytoskeletons of other cells or the extracellular matrix
anchoring junctions that connect the cytoskeletons of adjacent cells using cadherins (critical link)
adherens junctions
anchoring junctions that connect the actin filaments of one cell with those of neighboring cells or with extracellular matrix (critical link in this is integrin)
communicating junctions
chemical or electrical signal passes directly from one cell to an adjacent cell
gap junctions
communicating junctions in animal cells
communicating junctions in plant cells
-contain central tubule that connects the ER of the two cells

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