What are the three steps of cell signaling and what happens in each step? Flashcards
3 Stages of Cell Signaling
Signal Reception
Signal Transduction
Cellular Response
signal reception
Signaling molecule (ligand) binds to receptor protein (Peptides, proteins, amino acids, lipids, gases,) Receptor protein changes shape
signal transduction
Relay signals from receptor(s) to target molecule(s)
Protein phosphorylation and dephosphorylation
Signal transduction pathway
Cellular response
Cell division
Regulation of transcription
Enzyme activation and inactivation
signal reception (repeat)
Signaling molecule binds to a receptor,
causing conformational change in receptor
Signal receptors in the plasma membrane
- G protein-coupled receptors (GPCRs)
- Receptor tyrosine kinases
- Ion channel receptors
are there signal receptors else where
intracellular
In cytoplasm, nucleus, organelle
Signal transduction (repeat)
Cascades of molecular interactions transmit signals from receptors to relay molecules in the cell
What kind of pathway is transduction
Signal transduction pathways
What kind of signal transduction is common
Protein-protein interactions
Protein phosphorylation and dephosphorylation
What is happening in transduction pathway
Series of different proteins in a pathway are phosphorylated in turn, each adding a phosphate to next protein in line
Phosphorylation cascade in transduction pathway
- Kinase phosphorylates protein (active form)
- Phosphatase dephosphorylates protein (inactive form)
Cellular response
- Cell signaling leads to regulation of transcription
- Growth factor binds to receptor
- Phosphorylation cascade
- Last activated kinase enters nucleus
- Activates transcription factor (stimulates transcription)
- mRNA translated to protein
cellular response simplified
transcription stimulated by growth factor
mRNA translated to protein
What are some cellular responses to signal transduction
- activates succession of relay molecules including cAMP and 2 protein kinases
- cell proliferation, death, differentiation, and metabolism
Which of the following is NOT a common second messenger in cell signaling? A. Ca2+ B. Cyclic adenosine monophosphate C. Diacylglycerol D. Tyrosine E. Inositol trisphosphate
D. Tyrosine
A cell expresses a transmembrane protein that is cleaved at the plasma membrane to release an extracellular fragment.
The fragment binds to receptor proteins on nearby cells and activates signaling pathways resulting in altered gene expression patterns in the cells. What form of intercellular signaling does this represent?
A. Contact-dependent signaling
B. Paracrine signaling
C. Synaptic signaling
D. Endocrine signaling
B) Paracrine signaling acts on neighboring cells via local mediators.
Sort the following events to reflect the normal order in which they occur in G-protein-coupled receptor signaling leading to transcription of genes with cAMP response elements.
(A) Binding of CREB to PKA
(B) Binding of cAMP to PKA
(C) Dissociation PKA into catalytic/regulatory subunits
(D) Activation of adenylyl cyclase
DBCA Activation of adenylyl cyclase Binding of cAMP to PKA Dissociation of PKA into catalytic & regulatory subunits Binding of CREB to PKA
Which of the following events normally activates a GTP-binding protein?
A. GTP hydrolysis by the protein
B. Activation of upstream GTPase-activating protein
C. Activation of an upstream guanine nucleotide
exchange factor
D. Phosphorylation of a bound GDP molecule by an
upstream phosphorylase
E. Pi release after GTP hydrolysis
C) Activation of an upstream guanine nucleotide exchange factor
