Cell signaling
Response to stimuli -Every cell whether it is a unicellular organism Or a
multi cellular organism All cells respond to stimuli
Receptors and signal molecules
The ability to respond depends on the presence of receptors on the plasma
membrane. There are “signal molecules” that bind to the receptors and bring
about changes in the behavior and functioning of the cell.
Responses-
The cell response can be a change in
a. metabolism,
b. movement,
c. proliferation,
d. differentiation and
e. cell death.
Cell signaling
Cell signaling is possible due to production of certain signal molecules that
carry the message to other cells that are nearby or far away.
There are different types of cell-cell
signaling –
a. Endocrine signaling-Hormones
are secreted by
endocrine glands carried through the
blood stream to act on target cells at
distant body sites. Pituitary secretes
various hormones and the target sites
are ovaries and testis.
b. Paracrine signaling
– A cell secretes a molecule that acts on neighboring target
cells.Neurotransmitters at the site of
synapse. The Axon produces a chemical
like acetylcholine which acts on the
dendrite.
Some cells respond to signal molecules
on the plasma membrane of a nearby
cell but it is not secreted into the
extracellular fluid. This is useful for cell-cell
interactions during embryonic development.
, c. Autocrine signaling-
A cell is affected by its own signaling
molecules.- T lymphocytes produce
growth factors in response
to an antigen which triggers their
division. A cancer cell produces growth
factors to which it also responds.
The steps in cell signaling-
First the cell releases a signal molecule.
(Example-Amino acids or amino acid derivatives,
gases such as NO and CO,
steroids, steroid hormones,
Eicosanoids, polypeptides and proteins)
Response
The other cells can respond only if they have a receptor that recognizes and
binds to the molecule.
The binding of the signal with the receptor happens at the extracellular
surface of the responding cell.
( example –G-protein receptors or GTP binding
receptors. Protein tyrosine kinases, ligand gated
channels, steroid hormone receptors)
Relay of information
This causes a signal to be relayed across the
membrane to the cytoplasmic domain or region of
the receptor.
Once it reaches the inner surface of the plasma
membrane the signal is transmitted by two
major routes to the interior of the cell-
First route-
• The signal is transmitted from the
cytoplasmic domain of the receptor to a
nearby enzyme
The enzyme generates
• a second messenger.
• Such enzymes are called
• effectors.
Response to stimuli -Every cell whether it is a unicellular organism Or a
multi cellular organism All cells respond to stimuli
Receptors and signal molecules
The ability to respond depends on the presence of receptors on the plasma
membrane. There are “signal molecules” that bind to the receptors and bring
about changes in the behavior and functioning of the cell.
Responses-
The cell response can be a change in
a. metabolism,
b. movement,
c. proliferation,
d. differentiation and
e. cell death.
Cell signaling
Cell signaling is possible due to production of certain signal molecules that
carry the message to other cells that are nearby or far away.
There are different types of cell-cell
signaling –
a. Endocrine signaling-Hormones
are secreted by
endocrine glands carried through the
blood stream to act on target cells at
distant body sites. Pituitary secretes
various hormones and the target sites
are ovaries and testis.
b. Paracrine signaling
– A cell secretes a molecule that acts on neighboring target
cells.Neurotransmitters at the site of
synapse. The Axon produces a chemical
like acetylcholine which acts on the
dendrite.
Some cells respond to signal molecules
on the plasma membrane of a nearby
cell but it is not secreted into the
extracellular fluid. This is useful for cell-cell
interactions during embryonic development.
, c. Autocrine signaling-
A cell is affected by its own signaling
molecules.- T lymphocytes produce
growth factors in response
to an antigen which triggers their
division. A cancer cell produces growth
factors to which it also responds.
The steps in cell signaling-
First the cell releases a signal molecule.
(Example-Amino acids or amino acid derivatives,
gases such as NO and CO,
steroids, steroid hormones,
Eicosanoids, polypeptides and proteins)
Response
The other cells can respond only if they have a receptor that recognizes and
binds to the molecule.
The binding of the signal with the receptor happens at the extracellular
surface of the responding cell.
( example –G-protein receptors or GTP binding
receptors. Protein tyrosine kinases, ligand gated
channels, steroid hormone receptors)
Relay of information
This causes a signal to be relayed across the
membrane to the cytoplasmic domain or region of
the receptor.
Once it reaches the inner surface of the plasma
membrane the signal is transmitted by two
major routes to the interior of the cell-
First route-
• The signal is transmitted from the
cytoplasmic domain of the receptor to a
nearby enzyme
The enzyme generates
• a second messenger.
• Such enzymes are called
• effectors.
