Bio exam 230 week 6

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Describe the general process of signaling (including signals, receptors, second messengers and final target/effector).
- 1. Signal
- — chemical = ligand
- — ligand is the signal and binds to the receptor
- 2. Receptors
- — proteins that sense the signal
- — when Ligand binds to receptor usually results in conformational change of receptor (protein)
- 3. Transduction
- — signal is relayed through the cell using secondary messengers (not proteins)
- — effector (protein): target of signaling (can be several in a pathway)
- 4. Final effector: ultimate cellular change
Define protein conformation changes and how conformation changes result in changes in function.
- Signal (ligand) changes shape of the protein when it binds to the receptor
- Binding of ligand to receptor is specific and based on shape
- Receptor conformational (shape) change induces activity
- The structure typically involved in conformational change is the disruption of R-group bonds resulting in different structural motif interactions
GPCR
- Integral membrane protein
- G-Protein Coupled Receptors
- Iigand binding: outside
- G-protein binding: inside
- G-protein includes 3 subunits: alpha betta gamma
- Conformation change of GPCR after binding ligand triggers binding of GTP to G-alpha
- Activated G-alpha releases G-betta and G-gamma
- When betta and gamma are released they act as signaling molecules
- Both G-alpha and G-betta/G-gamma can further “transduce” the signal
RTK
- Receptor tyrosine kinase
- Binding of ligand causes conformational change of the receptor, causing monomers to come together (dimerize)
- When monomers come together tyrosine kinase domain phosphorylates tyrosines (autophosphorylation)
- Once activated, the RTK can phosphorylate other proteins
Compare and contrast peptide motifs and structural motifs.
- Peptide motif: sequence of AA
- Structural motifs: functional part of protein defined by the secondary structure; cannot function w/o rest of protein
Describe how cAMP is synthesized in the cell.
- Associated with GPCR pathways
- Forms the region where ligand will bind
- After ligand binding the activated G-alpha stimulates enzyme adenylyl cyclase
- This uses ATP to make cAMP
Describe how DAG/IP3 are synthesized in the cell.
- Ligand binding causes activation of phospholipase C (PLC)
- PLC cleaves the fatty acid chains of a phospholipid (PIP2)
- This results in IP3 and DAG
- DAG remains bound to the membrane
- IP3 binds to ligand-gated Ca++ channel in ER and causes calcium to enter the cytoplasm, causing a intracellular activity change
Integrate how receptors lead to the production of second messengers.
- Second messengers continue to transduce the signal in the cell
- Primary messengers generates the second messenger; typically generated near the receptor
- Second messengers typically interact with a protein (effector) to cause a change
Interpret example signaling pathways from ligand to final target including:
- Target proteins carry out the response initiated by the signal
- Final target: biological response; can alter gene expression or alter existing proteins to cause a change

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Bio exam 230 week 6

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Week 6

Updated

2020-02-26T08:04:24Z

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