Cell-to-cell communication
this type of communication is essential for multicellular organisms
chemical messengers
cells in a multicellular organism communicate by using these
local signaling
this type of cell-to-cell communication sometimes has cell junctions that directly connect the cytoplasm of adjacent cells (cells of the immune system do this);
this type of cell-to-cell communication also may use local regulators that travel short-distan
local regulators
these are messenger molecules that travel only short distances through the interstitial fluid
direct contact and local regulators
these are the two ways that local signaling occurs
long-distance signaling
in this type of cell-to-cell communication hormones travel through the bloodstream to signal cells in other parts of the body (the endocrine system works this way)
1. reception
2. transduction
3. response
these are the three processes that cells receiving signals go through
reception
this process is when a ligand binds to a highly specific receptor protein, causing it to change shape
ligand
a signal molecule
plasma membrane proteins
most signal receptors are these
intracellular receptors
these receptor proteins are found in the cytosol or nucleus of target cells; small or hydrophobic chemical messengers (i.e. steroids & thyroid hormones) can easily cross the membrane to activate these receptors, thereby turning on specific genes
plasma membrane receptors
most water-soluble signal molecules bind to receptor proteins located here
1. G-protein-linked receptors
2. Receptor tyrosine kinases
3. Ion channel receptors
these are the 3 main types of membrane receptors
G-protein
this type of protein acts as an on/off switch
G-protein-linked receptor
this is a plasma membrane receptor that works with the help of a G protein (on/off switch)
Receptor tyrosine kinases
this is a plasma membrane receptor that can trigger multiple signal transduction pathways at once
receptor tyrosine kinases
these are membrane receptors that attach phosphates to tyrosines
ion channel receptor
this is a plasma membrane receptor that acts as a gate when the receptor changes shape
ion channel receptor
when a ligand binds to this kind of receptor, a gate allows specific ions (like sodium or calcium) to pass through a channel in the receptor
transduction
this process involves cascades of molecular interactions that relay signals from receptors to target molecules in the cell; usually involves multiple steps
multistep pathways
these pathways in transduction can amplify a signal so that a few molecules can produce a large cellular response, thereby providing more opportunities for coordination and regulation
second messengers
these are small, nonprotein, water-soluble molecules or ions that can readily spread throughout cells by diffusion; many trigger cyclic AMP or cAMP
first messenger
this is the extracellular signal molecule (ligand) that binds to the membrane (triggering the transduction pathway)
Cyclic AMP (cAMP)
this is one of the most widely used second messengers; when the first messenger binds to the receptor, it causes an enzyme in the plasma membrane to convert ATP to this (the second messenger)
cytoplasm and nucleus
these are the two places where responses may occur after transduction (leading to regulation of cellular activities)
1. amplifying the signal (and thus the response)
2. contributing to the specifity of the response
these are the two important benefits to multistep pathways
inactivation mechanisms
these are an essential aspect of cell signaling because they remove the signal molecule to prevent it from going on and on and on after it leaves the receptor and the receptor reverts to its inactive state
c
Which of the following is how hormones work?
a) chemicals released by a cell travel through the IF, bind to receptors on nearby cells & cause a response
b) a message is sent from one cell directly to another through gap junctions
c) chemicals released by
c
Which of the following gives a correct & broadest description of signal transduction pathways?
a) binding of a signal molecule to a cell protein
b) catalysis mediated by an enzyme
c) binding of a ligand to a receptor causes a sequence of changes in a seri
d
A steroid hormone is bound by an intracellular receptor. When it does, the resulting complex is most likely to do which of the following?
a) open channels in the membrane for other substances to enter
b) open channels in the nuclear envelope for cytoplasm
b
Which choice CORRECTLY describes what happens during the transduction part of a signal transduction response pathway?
a) some fraction of the original signal is converted into something else and passed through the cell.
b) changes in protein activities an
d
which best describes what a plasma membrane-spanning receptor actually does upon reception of a signal?
a) the receptor binds an extracellular signal molecule and passes it into the cell
b) activated receptors directly produce a response to the signal
c)
d
Which of the following statements CORRECTLY describes the use of ligand-gated ion channel receptors?
a) ligand binding is irreversible, resulting in a permanent change in this ion channel's activity
b) the binding site of this type of receptor is most oft