What must occur for a message to be sent from the outside of the cell to
inside the cell?
a. a signaling molecule binds with a membrane protein.
b. transport proteins form a channel for a large molecule.
c. enzymes inside the cell catalyze a reaction.
d. a small, nonpolar molecule crosses the membrane.

Radiometric dating is used to tell the absolute age of materials by studying the decay rate of radioactive isotopes. the decay rates of isotopes are constant and are expressed as .

What sre the effects of hemolytic disease of a newborn

The ancestors of plants that lived in water had plenty of water for the young. angiosperms are a group of land plants that evolved a reproductive trait for living on land. this trait protect young plants by allowing them to grow only when water is present and the conditions for healthy development are right. what trait most likely young angiosperms in this way?