G
Gases
An aeriform fluid that possesses complete molecular mobility and the property of indefinite
expansion. A gas has no definite shape, and its volume is determined by its container and by
temperature and pressure.
G protein
A GTP-binding protein that relays signals from a plasma-membrane signal receptor, known
as a G-protein linked receptor, to other signal-transduction proteins inside the cell. When
such a receptor is activated, it in turn activates the G protein, causing it to bind a molecule
of GTP in place of GDP. Hydrolysis of the bound GTP to GDP inactivates the G protein.
G-protein linked receptor
A signal receptor protein in the plasma membrane that responds to the binding of a signal
molecule by activating a G protein.
G 0 Phase
The G 0 phase (G sub 0) or G zero is a period in the cell cycle where cells exist in a quiescent
state. G 0 is sometimes referred to as a "post-mitotic" state since cells in G 0 are in a non-
dividing phase outside of the cell cycle;
G 1 phase
The first growth phase of the cell cycle, consisting of the portion of interphase before DNA
synthesis begins.
G 2 phase
The second growth phase of the cell cycle, consisting of the portion of interphase after DNA
synthesis occurs.
Gallbladder
A small, pear-shaped muscular sac, located under the right lobe of the liver, in which bile
secreted by the liver is stored until needed by the body for digestion.
Golgi apparatus
The golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898
by the Italian physician Camillo Golgi and was named after him.