Exam 2 (4) - Cell Communication Flashcards
What is the order in which we respond to a change in the environment?
stimulus–> receptor–> control center–> effector
what is true about responding to change in the environment?
order is the same between simple or complex cells
(all living things can detect change = signal transduction)
What are the different types of signaling?
- Direct signaling
- Contact-dependant
- Autocrine
- Paracrine
- Endocrine Signaling
What is Direct Signaling?
- gap junctions
- signal passes through gap junction to adjacent cells
- ex. cardiac muscle, neurons
What is Contact Dependent signaling?
- membrane bound signals that bind to receptors.
- ex. immune system –> antigen presenting cells ( phagocytosis)
Autocrine
- cells release signals that affect themselves and some neighboring cells
Paracrine
- only affect immediate neighbors ( like autocrine excluding itself)
- ex. synaptic cleft ( rapid diffusion of neurotransmitter)
Endocrine signaling
- group of specialized cells in an organ that releases hormones
- signals that travel long distances to affect larger cells
-ex. glands
WHat is signal transduction at a cellular level?
- Mechanism by which cells share information. Receive information generate a response
Signal Transduction: Stage 1
Receptor Activation
- some signal molecule ( lingal) binds to a receptor
receptor ligand interaction leads to STP
Signal Transduction: Stage 2
Signal Transduction Pathway
- specific interactions
- creating a change
- proteins go conformational changes ( catalyse other reactions)
Signal Transduction : Stage 3
Cellular Response
-depends on cell and signaling molecule
- ex.
- altered metabolism or other cell functions
- altered cell shape
- altered gene expression
- etc.
agonist?
a ligand that ENHANCES cellular activity
antagonist?
a ligand that BLOCKS cellular activity.
what are the different kind of receptors?
- intracellular receptors
- cell surface receptors
How does an intracellular receptor work?
They respond to signaling molecules that can diffuse through the membrane.
- lipids are soluble in other lipids
- ex. steroid hormones, auxins
- can attach to receptors in cytoplasm or directly onto DNA ( w/ Hormone Responsive Elements)
Where are the intracellular receptors located
-cytosol or nucleus
What are the forms cell surface receptors can take?
- ligand gated ion channels
- enzyme linked receptor
- G coupled protein
Where are ligand gated ion channels common?
- nerve and muscle cells
What do the ligand gated ion channels do?
- help create action potentials
What are two features of enzyme linked receptors?
- extracellular domain
- catalytic domain
What is the extracellular domain?
- hydrophilic
- interacts w/ some signaling molecule
What is the catalytic domain?
- part of the receptor involves a chemical reaction
- some kind of kinase is involved ( 3 are common)
What does kinase do?
phosphorylates –> activates
What does it mean to phosphorolate?
- take phosphate from ATP and attach it to something else –> energy
what does phospotase mean ?
- dephosphorylate ( opposite of kinase)
What are the 3 subunits of G proteins?
- a
- B
-y
What happens after a signaling molecule binds to a GPCR in a plasma membrane?
GDP molecule is exchanged for GTP inside the cell
What is GDP/GTP?
equivalent to ATP and ADP = E
What does the G stand for in GDP and GTP?
Guanine
What happens once GTP is available?
- subunits disassemble
- cellular response is triggered
What terminates the cellular response of GPCR?
Hydrolysis of GTP–> GDP
What does cAMP do as a second messenger?
- activate or inactivate proteins w/in the cell
- 2nd messenger
When is the signal terminated for cAMP?
- phosphodiesterase
- converts cAMP to AMP
What is considered the extracellular domain in the GPCR?
The G protein-coupled receptor outside of the cell.
What is the catalytic domain of the GPCR?
The heterotrimeric G protein
What is the epidermal growth factor? what is it an example of?
It is an example of the enzyme-linked receptor
- tissue repair, mitosis
What is the 2nd messenger mechanism?
Producing a small molecule that can relay a signal inside the cell.
why does there need to be a 2nd messenger?
1st messenger cannot cross into membrane
can only do its job by interacting w/ receptors in the membrane.
What is important to remember about receptor pathways?
The cAMP can be stimulatory at times and then inhibitory at times. ( depends on receptor and cell shit)
What are two traits of a 2nd Messenger?
- short life span
- increase amplification/speed
How is the DAG/IP3 2nd messenger mechanism different to cAMP?
It ends up having 3 -2nd messengers.
What are the 3 messengers made in the DAG/IP3 mechanism?
-DAG
-IP3
-Calcium
What is step 1 of the cAMP cycle?
- signal molecule interacts with GPCR–> activates it
What is step 2 of the cAMP cycle?
GTP and G protein bind
- subunits dissasociate
What is step 3 of the cAMP cycle?
- subunit binds to the effector ( adenylate cyclase)
-synthesis of cAMP
What is step 4 of the cAMP cycle?
- activates kinase
What is step 5 of the cAMP cycle?
-kinase phosphorylates, cause specific reactions
What is the relay GTP?
Inhibits effector enzymes.
What is Step 1 of the DAG/IP3 mechanism?
- signal molecule interacts with GPCR–> activates it
What is Step 2 of the DAG/IP3 mechanism?
- GTP and G protein bind
- subunits disassociate
What is step 3 of the DAG/IP3 mechanism?
- subunit binds to the effector ( phospholipase)
What is step 4 of the DAG/IP3 mechanism?
- breaks down membrane phospholipid into 2–> 2nd messenger molecules. ( DAG/IP3)
What is step 5 of the DAG/IP3 mechanism?
- DAG activates kinase C
- IP3 binds to smooth ER–> Calcium Released
What is step 6 of the DAG/IP3 mechanism?
- 3-2nd messengers direct responses of the target cell
Where does DAG go? What does it do?
- inside membrane
- hydrophobic
- activates kinase C
Where does IP3 go? What does it do?
- into cytoplasm
- binds to smooth ER–> calcium is released
