Chapter 11: Cell Communication Flashcards
can signal to each other and interpret the signals they receive from other cells and the
environment
cells
are most often chemicals
signals
Any molecule that is binding superficially to the receptor.
ligand
what does communications among microorganism do
how cells
receive
send
respond to signals
has two
mating types, a and α
Saccharomyces cerevisiae
how do cells of different mating types locate each other
via
secreted factors specific to each type
initiates a series of steps called a signal transduction
pathway
binding of a mating factor at the cell surface
were
adopted for use in their multicellular descendants
signaling molecules
is critical among prokaryotes
cell signaling
allows
bacteria to sense local population density in a
process called quorum sensing
concentration of signaling molecules
the regulation of gene expression in response to fluctuations in cell-population density
quorum sensing
example of quorum sensing
formation of biofilm
or
secretion of toxins by infectious bacteria
is an aggregation of bacterial cells adhered to
a surface
biofilm
Interfering with the signaling pathways used in quorum
sensing may be a promising approach as an what
alternative to antibiotic treatment
Cells in a multicellular organism communicate via what
signaling molecules
animal cells may communicate by
direct contact
local signaling
directly connect the cytoplasm of adjacent cells
cell junctions
Signaling substances in the cytosol can pass freely
between what
adjacent cells
animal cells communicate using
secreted messenger molecules that travel only short
distances
paracrine signaling
which stimulate nearby target cells to grow and divide
growth factors
occurs in the animal nervous
system when a neurotransmitter is released in
response to an electric signal
Synaptic signaling
Local signaling in plants is not well understood
beyond communication between what
plasmodesmata
meaning
to stimulate, or set in motion
hormone
Compound produced in one part of the
body and then transported to other parts
of the body where it triggers responses in
target cells and tissues.
hormone
what do long distance signaling use
hormones
Hormonal signaling in animals is called
endocrine signaling
specialized cells release hormones, which
travel to target cells via the circulatory system
endocrine signaling
The ability of a cell to respond to a signal depends
on whether or not what
it has a receptor specific to that signal
the target cell detects a signaling
molecule that binds to a receptor protein on the cell
surface
reception
the binding of the signaling molecule
alters the receptor and initiates a signal
pathway;
transduction
the transduced signal triggers a specific
response in the target cell
response
a signal molecule
ligand
the initial transduction of the signal
A shape change in a receptor
Most signal receptors are what
plasma membrane proteins
three types of signal processes
receptions
transduction
response
three types of membrane receptors
- G-protein linked receptors
- Tyrosine-kinase receptors
- Ion-gated receptors (voltage gated)
are the largest
family of cell-surface receptors
G protein-coupled receptors (GPCRs)
G-protein signal transduction pathway steps
- Signal binds to G-protein receptor
- Converts GDP to GTP
3.Active G-protein binds to another enzyme - This triggers The next step in the pathway
- The G-protein acts as its own enzyme, GTPase, and
Hydrolyzes the GTP to GDP and becomes inactive again
many diseases such as
cholera, botulism and other vitamin deficiency
disorders are due to
malfunctioning G proteins
G-proteins with a GDP (Guanosine Diphosphate) are considered what
inactive
G-proteins with a GTP is considered what
active
Changes in relay proteins are affected by
conformational changes involving what
phosphorylation
an enzyme that transfers phosphate groups from the ATp tp protein
Involves protein kinase
the signal is transmitted by a series or “cascade” of
protein phosphorylations, each resulting in a
conformational change of the protein
(enzyme).
Phosphorylation Cascade
what changes a protein from an inactive to active form.
shape change in a Phosphorylation Cascade
are involved in deactivating active proteins by removing a phosphate group
protein phosphates
example of Second Messengers in Transduction Pathways
Cyclic Adenosine monophosphate (cAMP)
Inositol Triphosphate (IP3) AND Ca 2+
can readily spread throughout the cell by
diffusion
Second Messengers in
Transduction Pathways
cholera infections linked to what
g-protein recoetors
what caused cholera
bacterium (Vibrio cholerae) it is from contaminated water.
cholera bacteria modifies G-protein involved in what
regulating salt and water secretion
what does cholera do the G-protein
it cant hydrolyze to GTP to GDP therefore it is always active
is stimulated continuously to make cAMP
Adenylyl cyclase
Trigger more than one signal transduction pathway
at once
Tyrosine-Kinase Receptors
Often involve growth factor molecules (PDGF) as
chemical signals
Tyrosine-Kinase Receptors
transfers phosphate group from ATP to Tyrosine
Kinase
Before the signal molecule binds, the tyrosine-kinase receptors exist as individual what
polypeptides
what do the receptor polypeptides consist of
– Extracellular signal binding site
– Intracellular tail containing several tyrosines
– A single helix spanning the membrane
the steps of TYROSINE-KINASE ACTIVATION
- Signal binding to tyrosine-kinase receptor
causes the T-K receptor to bind to another
T-K receptor producing a dimer - T-K enzyme phosphorylates the Tyrosine
proteins on the opposite receptor - Relay proteins attach at the
phosphorylated tyrosines and become
active
Channels in these membrane proteins either open or close in response to a chemical signal (ligand) allowing or
blocking the flow of specific ions (such as Na+ or Ca2+)
Ion-Channel Receptors
A specific ligand binds on the
extracellular side of the membrane
Ion-Chanel Receptors
Not ALL Receptors are what
membrane proteins
where are other places that receptor proteins are located?
cytoplasm or
nucleus of target cells.
To reach non membrane protein receptor, a chemical messenger must be able to what
pass through the membrane (HYDROPHOBIC)
examples of non membrane protein recepetors
Steroid hormones (testosterone)
• Thyroid hormones
• Nitric oxide (NO); small gaseous molecules
Secreted by testis cells
testosterone
steps of how testosterone works
- Secreted by testis cells
- The hormone travels through the blood
and enters cells all over the body - Target cells have testosterone receptor
molecules in their cytosol; the hormone
binds to the receptor, activating it. - The active form of the receptive protein then
binds to DNA directly and turns on genes in
the nucleus that control male sex
characteristics - The receptor carries out the complete
transduction of the signal.
a molecule or molecular complex consisting of two identical molecules linked together.
dimer
what binds on the extracellular side of a ion channel receptor
A specific ligand
