lecture 4 Flashcards
1
Q
nuclear and cytoplasmic responses
A
- signal transduction > regulation of cellular activities ( responses may occur in nucleus or cytoplasm)
- many signaling pathways regulate synthesis of enzymes/other proteins (usually by turning genes on/off in nucleus)
- activated molecule in signallng pathway may fxn as transcription factor
2
Q
hydrophobic signals
A
- steroids
- retinoids
- thyroxine
- to cytosilic receptor
- modification of gene expression/development
3
Q
hydrophilic signals
A
- small molecules
- peptides
- proteins
- to inactive cell-surface receptor (becomes active)
- to signal transduction proteins and second messengers
- to effector protein
- modification of gene expression/development
4
Q
nuclear responses
A
- pathways regulate synthesis of enzymes/other proteins
- turn on/off genes in nucleus
5
Q
cytoplasm responses
A
- reception
– binding epinephrine to G protein-coupled receptor
– final activate molecule is enzyme/glycogen phosphorylase which catalyse hydrolysis of glycogen into glucose - transduction
– inactive G protein to active
– inactive adenylyl cyclase to active
– inactive protein kinase A to active
– inactive phosphorylase kinase to active
– inactive glycogen phosphorylase to active - response
– glycogen to glucose-1-phosphate
6
Q
regulation of responses
A
- amplification
- specificity
- effeciency
- termination
7
Q
amplification
A
- at each catalytic step, number of activated products can be increased in previous step
- eg. epinephrine-triggered pathway
8
Q
specificity
A
- cells constantly exposed to different signaling molecules in blood
- some messengers trigger responses in only one type of cell, others more than one
- particular proteins of cell determine signalling molecules/nature it responds to
9
Q
effeciency
A
- signalling pathway diagrams are necessity (over-simplified) for ease of understanding
- scafolding proteins can increase signal transduction effeciency (grouping together different proteins involved in same pathway)
- scaffolding proteins may help activate some relay proteins
10
Q
termination
A
- inactication mechanisms are essential
