[WG21]
Nernst equation
Ek = RT/FZk ln{[Ko]/[Ki]}
= 61.5 log{[Ko]/[Ki]}
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[WG21:p42]
G protein - 3 subunits: alpha, beta, and gamma
On activation, alpha separates from beta and gamma
Alpha subunit then has intrinsic GTPase activity
When the GTP converts back to GDP, alpha reassociates with beta+gamma subunit
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[WG21:p42]
Phospholipase can be activated by either Gq protein or tyrosin kinase-linked receptors
--> Converts PIP2 (phosphatidylinositol 4,5-diphosphate) into IP3 and DG (diacylglycerol)
IP3 (diffuse to endoplasmic reticulum) triggers release of Ca2+ from ER into cytoplasm
DG (stays in the cell membrane) actives protein kinase
=====
[WG21:p44]
Gi inhibits adenylyl cyclase
Gs stimulates adenylyl cyclase
cAMP is converted from ATP by adenylyl cyclase
cAMP is inactivatd by phosphodiesterase, which coverts it into 5'-AMP
cAMP then activates protein kinase A
Protein kinase A phosphorylate proteins and altering their activity
Phosphodiesterase is inhibited by methylxanthines (e.g. caffeine, and theophylline)
=====
[WG21:p49]
Theories of aging
1. random mutation with accumulation of DNA abnormalities
2. Increased cross-linkage of collagen and other proteins
3. Cumulation of damages by free radicals
Caloric restriction prolong life span, probably due to decreased formation of protein cross-links and decreased production of free radicals