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gap junctions
direct contact
local regulators
growth factors & neurotransmitters
hormones
long distance
3 stages of cell signaling
reception
reception
detection of a signal molecule (ligand) coming from outside the cell
plasma membrane receptors
water soluble ligands
intracellular receptors
inside the cell
cytoplasm
nucleus
G-protein coupled receptors
G-protein + GTP activates enzyme = cell response
Tyrosine Kinase receptor
insulin receptor
dimer forms upon ligand binding
activates multiple cellular responses at once
ligand-gated ion channel
signal receptor changes the shape (opens & closes)
regulates flower of specific ions
transduction
convert signal to form that can bring about a cellular response
cascades of molecular interactions relay signals
protein kinase (enzyme that phosphorylates & activates proteins)
second messengers
small
response
response to the signal molecule
regulate protein synthesis by turning on/off genes in nucleus
regulate activity of proteins in cytoplasm
Apoptosis
programmed cell death
signals activate cascade of "suicide" proteins
protect neighboring cells from damage
Short-distance communication
Cell sends out local regulators (signals) Target cell is within a short distance of the signal Often used to communicate with cells of the same type
Long-distance communication
Traget cell is not in the same area as the cell emitting the signal Signal travels a long distance to reach the target cell Often used to signal cells of another type
mutation in transduction pathways
One disruption in a pathway can affect the downstream reactions
change in function
the cell cycle
interphase (growth & reproduction) m-phase (mitosis - division of nucleus
Interphase
G1 (cell growth) S (copies of DNA are made) G2 (the cytoplasmic components are doubled in preparation for dvision)
Mitosis
growth
Mitosis process (PMAT. . .C)
Prophase
Nuclear envelope begins to disappear
DNA coils into visible chromosomes
Fibers begin to move double chromosomes toward the center of the cell
Metaphase
Fibers align double chromosomes across the center of the cell
Anaphase
Fibers separate double chromosomes into single chromosomes (chromatids)
Chromosomes separate at the centromere
Single chromosomes (chromatids) migrate to opposite sides of the cell
Telophase
Nuclear envelope reappears and establishes two separate nuclei
Each nucleus contains a complete genome
Chromosomes will begin to uncoil
Cytokinesis
seperates into two daughter cells
ensures each equal distribution of cytoplasm
regulation checkpoints
G1 Checkpoint
At the end of the G1 phase
Cell size check
Nutrient check
Growth factor check
DNA damage check
G2 Checkpoint
At the end of G2
DNA replication check
DNA damage check
M-spindle Checkpoint
Fiber attachment to chromosome check
cyclins
proteins that regulate the cell cycle
Used to activate cyclin-dependent kinases
cyclin-dependent kinases
Group of enzymes involved in cell cycle regulation Requires cyclin binding for activation Phosphorylate substrates
disruptions in cell cycle
may result in cancer and/or apoptosis
Cancer is the result of an unregulated cell cycle with uncontrolled cell divison
feedback
homeostasis (stable internal enviorment)
target set point
negative feedback
maintain homeostasis for a particular condition by regulating physiological processes RETURNS SYSTEM BACK TO ITS TARGET SET POINT
positive feedback
The variable initiating the response is MOVED FARTHER AWAY FROM THE INITIAL SET POINT
cell signaling pathways are activated by. . .
cell-to-cell communication
an example of long-distance communication are . . .
hormones
cAMP activates. . .
protein kinase A (phosphorylates various other proteins) ~ type of ernzyme
what occurs first once a chemical messenger reaches a target cell?
a ligand binds to a receptor
cell signaling starts with. . .
the reception of the signal
only cells with correct receptor can respond
Increased cell division will lead to. . .
the formation of a tumor
DNA replication occurs during. . .
the S phase (requires free nucleotides) - if unavailable
Note 
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