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Midterm

BIO315H5 Study Guide - Midterm Guide: Gtpase, Cell Membrane, Conformational Change


Department
Biology
Course Code
BIO315H5
Professor
Hai- Ying Mary Cheng
Study Guide
Midterm

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5 ways in which Dynamic Range can occur
1. Receptor Sequestration
-when activated receptor, can be internalized & kept in intracellular cell vesicles
2. Receptor Down-regulation
-oce receptor iteralized, does’t stay, gets degraded
3. Receptor Inactivation
-activated receptor triggers signalling evens that inactivate the receptor
4. Inactivation of signalling protein
-iactiatio of a sigallig protei that’s dostrea of the receptor
5. Production of Inhibitory Protein
-inhibitory protein stops further signalling from receptor to downstream signalling events
Adaptation/Desensitization enables a cell to respond to a wide range of signal concentrations
-negative feedback gives rise to adaptation with short delays
-if have prolonged exposure to stimulus, & is through cellular signal, the response of cell to signal
increases overtime (through negative feedback)
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GPCR signals through activation of Heterotrimeric Proteins
3 subunits: alpha, beta, gamma (beta-gamma subunits form obligate dimmers)
In INACTIVE state alpha subunit has GTPase activity (hydrolyzes GTP to GDP)
Have lipid anchors (covalently attached) to plasma membrane
Defined by their alpha subunit. Have different types, which bind to different subsets of GPCRs
and activate different subsets of intracellular signaling cascades
Activation of Heterotrimeric G-protein
1) Inactive GPCR
2) Signal molecule binds (active GPCR)
3) Causes conformational change in alpha subunit
4) Allows GDP to come off & GTP binds in place
5) Causes G-protein to be active and for B dimer to dissociate
Either allows to interact with heterotimeric G-protein or hetero may already be associated with
inactive receptor
When active, GPCRs act as GEFs for heterotrimeric proteins
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