Production or consumption of chemicals by cytosolic metabolism can create steep concentration gradients for those chemicals across the plasma membrane. Active transport or co-transport of chemicals can also be used to create steep concentration gradients across the plasma membrane. When chemical A is co-transported with chemical B, diffusion of B down a chemical gradient is tightly coupled to creation of a chemical gradient for A. 16. Describe three basic mechanisms by which the activity of a protein can be changed during cell signal transduction, specifically addressing the speed of each mechanism. Epinephrine increases the level of cAMP in liver cell cytosol.
Epinephrine binds to a G-protein coupled receptor in the plasma membrane.