The lifetime of an intracellular signaling molecule must be short for the cell to be able to cause a change in the concentration of the signaling molecule in an efficient manner. PKA is more closely related to PKC than to PKG at the amino acid level. Components of intracellular signaling pathways can be small molecules,

Atennis club charges a monthly membership fee of $150 and charges it members $10 per hour to use a court. there's also $500 fee to become a member. stella joined the tennis club last spring, and she has been a member for 5 months. she has been playing 10 hours of tennis each month. stella values an hour of her time at $20. during a boring afternoon meeting, stella thinks about reserving a court to work on her serve for an hour tonight. what's stella's opportunity cost of working on her serve for an hour?