5.6: The plasma membrane plays a key role in most cell signaling Flashcards
local regulators
they are signaling molecules dissolved in the cytosol that are used to communicate short distances, growth factors are good examples of these
Where do signaling molecules typically come from
from other signaling cells
Types of local signaling include…
direct contact through junctions, cell to cell rec. , paracrine, and synaptic signaling
Cell Junction
directly connect cytoplasms of very close cells, type of local signaling
Plasmodesmata
cell junctions but for plants
Paracrine signaling
where local regulators influence the cells in a certain vicinity
synaptic signaling
in the nervous system, a nerve cell is triggered by an electrical signal which makes the nerve cells secrete a neurotransmitter molecule carrying a chemical signal, these molecules then diffuse into the synapses
An example of long distance signaling is…
endocrine signaling
endocrine signaling
specialized cells release hormones, in animals, these hormones travel through the circulatory system, in plants they move through air and gas
hormones
used for long-distance signaling, many types
What are the 3 stages of cell signaling?
Reception, Transduction, and Response
Reception
The target cell’s detection of signal molecules when they bind
Where does reception usually take place
in the cell or on its membrane
ligand
general term for a signaling molecule with a receptor protein causes shape change in the protein when binded
Transduction
The conversion of the signal to a for that can bring about a specific cellular response, basically series of reactions happen to where it can make a response
signal transduction pathway
series of steps where a signal on a cell’s surface is converted into a specific response
Response
The specific cellular response to the signal molecules
What is the significance of the receptor protein changing shape when it binds to the signaling molecule
The binding of ligand and a receptor is very specific, the following shape change of the receptor molecule causes it to react with other cellular molecules
Intracellular receptors
found inside the plasma membrane in the cytoplasm/most often in the nucleus, ligand must be small and hydrophobic
Plasma membrane receptors
found in the plasma membrane, hydrophilic ligands
G protein-coupled receptor(GPCR)
surface transmembrane receptor that works with the help of a G protein, this type of reception is used by other hormones and neurotransmitters
G protein
Protein that is activated by exchanging its GDP with GTP
Step of 1 of G-protein-linked reception
- Ligand binds to G proteins-couples receptor(type of receptor)
- Makes a shape change in the receptor so it binds to inactive G protein
- This causes a GTP to replace GDP, thus activating the G protein(happens when G protein binds to the receptor)
Step of 2 of G-protein-linked reception
- The newly activated G protein binds to a specific enzyme(activates enzyme)
- This activation of the enzyme causes a cellular response(only one)
- The shape change is back to normal and the G protein hydrolyzes its GTP back to GDP to repeat the process after the receptor leaves
How does the G-protein-linked reception cause cholera
a high concentration of cAMP causes intestinal cells to secrete large amounts of waste
Step 1 and 2 of receptor tyrosine kinases
- The binding of signal molecules(two of the same type) to the receptors
- This causes the formation of a dimer
- dimer: structure of many tyrosine kinases that receives an ATP(phosphorylation) molecule
Step 3 and 4 of receptor tyrosine kinases
The inactive relay model becomes active by attaching to the receptor tyrosine kinase proteins(multiple responses based on number of Tyrosines)
What is the key difference between G-protein-linked reception and receptor tyrosine kinases
single ligand can activate with G-protein so single response, multiple cellular responses in tyrosine kinase depends on the number of phosphates attached
ligand-gated ion channel
Is a gate for ions when the receptor changes shape(gated ion channel)
explain how the ligand-gated ion channel works
when a receptor is bound to a ligand, the ion gate allows for specific ions to come in (opens and closes),these ions are moving down their electronegative gradient(facilitated diffusion), the process is reset through the receptor leaving
what systems require the ligand-gated ion channel
very important in the nervous system, diffusion of ions can cause an electrical signal
What are the 3 membrane receptors
G-protein-linked receptors, Receptor tyrosine kinases, and ligand-gated ion channel
What is an example of an intracellular receptor
Steroid Hormone Interacting with an Intracellular Receptor
Explain how a Steroid Hormone Interacting with an Intracellular Receptor works
- Aldosterone(steroid), can pass through the plasma membrane(hydrophobic ligand)
- This steroid binds to a receptor protein in the cytoplasm activating it(since in the cytoplasm, the transduction pathway is short)
- Hormone receptor complex(receptor bound to protein) enters the nucleus and binds to specific genes
- This steroid/hormone acts as a transcription factor, stimulates the transcription of the gene/DNA into mRNA
- mRNA is translated into a specific protein
Protein kinases
at each step these phosphorylate/activate many proteins at the next level(an enzyme that activates another enzyme until inactive protein is activated, info/phosphates are passed on)
Phosphorylation cascade
multistep pathway which amplifies the signal as the process goes on,phophoralyzation occurs as the name implies
when does the phosphorylation cascade stop
Goes until the protein that turns on the response is activated
benefits of a phosphorlation cascade
allows for a larger cellular response and more coordination opportunities
typically how many protein kinases are use
3
Protein phosphatases
removes the phosphate from protein kinases, a process called dephosphorylating(turns off signal)
what are the benefits of protein phophotases(pp)
They also make protein kinases available for reuse, enabling the cell to respond to the signal again
Second messengers
small, nonproteins, water-soluble molecules, or ions(Cyclic amp, Calcium ions)(only for plasma membrane receptors)
What is the main duty of the secondary messengers
The second messenger activates protein kinase A which then starts the phosphorylation cascade
What are examples of places where secondary messengers are used
These messengers can participate in pathways of G and tyrosine receptors
Cyclic AMP(cAMP)
is one of the most widely used second messengers, causes the start of protein kinase or protein kinase A
Adenylyl cyclase
an enzyme in the plasma membrane, converts ATP to cAMP(is ending in -ase then enzyme)
Phosphodiesterase
turns off cAMP
where is the cellular response the shortest?
the cytoplasm
Where does a cellular response usually occur
The response typically occurs in the cytoplasm(enzyme) or nucleus(protein)
what is the usual cellular response in the nucleus
The final activated molecules is usually a transcription factor
what is the usual cellular response in the cytoplasm
Activities in the cytoplasm include activating or inhibiting an enzyme, or cause cytoskeleton rearrangement
What is apoptosis
It is programmed cell suicide, can be triggered by, death signaling ligand, DNA damage in the nucleus, and protein misfolding in the endoplasmic reticulum
