Cell Communication And Signal Transduction Pathway Flashcards
What are the 3 stages of cell signaling?
Reception, transduction, response
What are the 3 types of cellular messaging?
Local signaling, local regulators, long distance signaling (hormones)
Local signaling
Animal and plant cell have cell junctions that directly connect to the cytoplasm of adjacent cells and signaling mediators in cytoplasm are passed directly
What is a type/ example of local signaling?
Cell to cell recognition
2 animal cells communicate by interactions of membrane receptors
Local regulators and 2 examples of it
A type of local signaling where messenger molecules travel short distances to bind to receptors of local regulators
Paracrine
Synaptic
Paracrine signaling
Growth factors are secreted which locally influence the growth and division of local cells
Synaptic signaling
Animal nervous system
Occur in narrow space between 2 nerve cells known as synapse
Neurotransmitters recreate chemical signal and it binds to receptors of adjacent cell to translate nerve impulse
Tf: both local and long distance signaling can recognize signaling moleutes given by specific target cells
Tru
What is the path of synaptic signaling?
Electrical signal → chemical signal → electrical signal
Long distance signaling
Hormones are an example of endocrine signaling in animals
Carried in the bloodstream
Plants also secrete hormones into the air to promote ripening
- Reception
Chemical signal detected when molecule binds to receptor
Inside or outside cell
Receptors are specific for certain ligand lock and key )
Ligand binding: change 3d shape of receptor → actives receptors → receptors interact with relay molecules
Ligand binding CAN: several receptors on cell membrane → further signal transduction
- Transduction
Bounded receptor changes to affect relay molecules in signal transduction pathway
- Response
Cellular response is triggered
Cellar response can be cytoplasmic cell processes) or nuclear(gene transcription)
Where are hormones made?
Brain and pancrease
Explain yeast
3 main categories of transmembrane receptors
G-protein coupled receptors
Receptor tyrosine kinases
Ion channel receptors
G-protein coupled receptors
① ligand binds to gpcr which turns on g-protein with conformation change
② The active g-protein binds to g-protein linked receptor where GDP → gtp phosphorylation and alpha subunit
Active g-protein is alpha subunits with gtp instead of GDP
③ activated g-protein binds to aderylyl cyclase by giving phosphate
④ g-protem is now inactive and retains to og
Receptor tyrosine kinases
① ligand binds to binding site found in extracellular domain and receptor tyrosine kinase gets phosphorylated
② 2 halves come together = dimer
③ tyrosine is activated by dimerization and each tyrosine kinase adds phosphate from ATP
④ this phosphate can binds with relay proteins
Ion channel receptors
Has gate and changes shape found in nervous system
① ligand bind
② channel gate opens and ions flow in
③ when concentration is reached the ligand unbinds
④ gate closes
Intracellelar receptors
Found in cytoplasm or nucleoplasm
Eg. Hormones testosterone
Are nonpolar/hydrophobic
Purpose of signal transduction pathway
Amplify signal
Better regulation and fire-tuning of signal
What are some ways pathways may active next protein
Phosphorlyation or de phosphorylation
-3d shape change
Releasing small molecules/ions like secondary messengers
Protein kinase
Enzyme transferring phosphate group from ATP to other molecules
Many relay molecules are protein kinase
Phosphorylation targets
Serine or threonine
Protein phosphates
Enzymes removing phosphate groups fromproteins which turn off signal transduction pathway
-Recycle protein kinase
What regulates activities on and off switch
Phosphorylation and dephosphorylation
Dependent on the balance of active kinase and active phosphates enzymes
Second messengers
Small water-soluble which pass through cell membrane by diffusion
Found in both g-protei coupled receptor and receptor tyrosine kinase
-Cyclic amp
-Calcium ions
C amp
Second messenger
Converts ATP → camp is what adenylyl cycles does
Camp is deactivated with phosphatase (dephosphorylation)
- eg. when it phosphorylates protemkinase A
Discovered by Sutherland when epinephrine caused glycogen to breakdown but nothing was passing though plasma membrane
Calcium ions
Second messenger
Stimulate growth factors, hormone andneurotransmittes
Using calcium flux
Which second messenger is more prominent camp or Ca
Calcium
What does Ca influence?
Muscle cell contraction
Secretion of certain molecules
Cell division
Nerve impulse
What is inositol triphophate IP3
Second messenger
Stimulate release of calcium ions from Er
Diacylglycerol DAG
Second messenger
Other signaling pathway not related to Ca release
What does pip 2 breakdown into
DAG IP3
How is pip 2 produced?
The cleavage of plasma membrane lipid cleaved in half to produce pip 2→ DAG and IP3
Nuclear cellular responses
Regulate protein synthesis in nucleus
- transcription factors work to turn off and on genes encoding for protein → mRNA → protein encoded by specific gene
Cytoplasmic cellular responses
Regulates protein function in cytoplasm
- opening and closing ion channels
- regulating enzyme functions
- fine-tuning metabolism
Scaffold protein
Large relay proteins to which several other relay proteas can attach to
Apoptosis
Programmed cell death
Which cells undergo apoptusts?
Infected cells, damaged, reached end of functional life span
Process of apoptosis
DNA and organelles are fragmented (packaged in vesicles)
Cell shrinks in size and bless are formed
Scavenger cells recognize apuptotic cells and engulf for safe disposal
How does apoptosis work?
Proteases called caspases are activated to degrade cellular protein
- 15 caspases involved in apoptotic pathurys
- signaling depends on which caspase
What is aprominent apoptotic pathway starter in cell
Leakage of proteins from mitochondria
Process of apoptosis signal
Cell death trigger(extrucellular) → pores of mitochondrial membrane → leakage of cytochrome c→ activates cell death protease ced-3, ced-4 (which is normally inhibit by ced-9
