BISC 1111 Chapter Notes - Chapter 11.1-11.4: Signal Transduction, Protein Kinase A, Paracrine Signalling

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Samuel Mohebban Chapter 11.1-11.4 Exam 2
1
Bacterial cells secrete molecules that can be detected by other bacterial cells.
o Quorum sensing- sensing the concentration of such signaling molecules allows bacteria to
monitor the local density of cells, a phenomenon called.
Animal cells may communicate via direct contact between membrane-bound cell-surface molecules
in a process called cell-cell recognition.
Growth factors are compounds that stimulate nearby target cells to grow and divide.
Paracrine signaling- numerous cells can simultaneously receive and respond to a signal produced by
a single cell in their vicinity.
Synaptic signaling- an electrical signal along a nerve cell triggers the secretion of neurotransmitter
molecules.
o These molecules act as chemical signals, diffusing across the synapse triggering a response in
the target cell.
Both animals and plants use chemicals called hormones for long-distance signaling.
Endocrine signaling- specialized cells release hormone molecules, which travel via the circulatory
system to other parts of the body where they reach target cells that can recognize and respond to the
hormones.
o Both animals and plants use chemicals called hormones for long-distance signaling
1.) Reception- target cell’s detection of a signaling molecule coming from outside the cell.
o A chemical signal is “detected” when the signaling molecule binds to a receptor protein
located at the cell’s surface (or inside the cell)
2.) Transduction- the binding of the signaling molecule changes the receptor protein in some way,
initiating the process of transduction.
o The transduction stage converts the signal to a form that can bring about a specific cellular
response.
o signal transduction pathway- transduction sometimes occurs in a single step but more often
requires a sequence of changes in a series of different molecules
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Samuel Mohebban Chapter 11.1-11.4 Exam 2
2
3.) Response- the transduced signal finally triggers a specific cellular response.
o The response may be almost any imaginable cellular activity like catalysis by an enzyme,
rearrangement of the cytoskeleton, or activation of specific genes in the nucleus.
The cell-signaling process helps ensure that crucial activates like these occur in the right cells.
The signaling molecule acts as a ligand- term for a molecule that specifically binds to another
molecule, often a larger one
o Ligand binding causes a receptor protein to undergo a change in shape.
A G Protein-coupled receptor (GPCR) is a cell-surface transmembrane receptor that works with the
help of a G protein- a protein that binds the energy-rich molecules GTP.
Many different signaling molecules use GPCRs.
o Ex: yeast mating factors, epinephrine, and many other hormones.
Receptor Tyronsine Kinases (RTKs) belong to a major class of plasma membrane receptors
characterized by having enzymatic activity.
o A kinase is any enzyme that catalyzes the transfer of phosphate groups.
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