[WG21]

Nernst equation

Ek = RT/FZk ln{[Ko]/[Ki]}
= 61.5 log{[Ko]/[Ki]}

 

=====

[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

 

====

[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