The human heart, composed of specialized muscle cells, beats to a specific rhythm. the heart cell rhythm partly depends on the opening and closing of series of gateways within the cell membrane, called ion channels. some channels let certain ions flow out, others let different ions flow in. the same membrane system is at work in other cells, to regulate what stays and what leaves the cell.
this cell membrane gateway system is specifically called the
a)
sodium-chlorine pump.
b)
hydrogen-oxygen pump.
eliminate
c)
sodium-potassium pump.
d)
calcium-potassium pump.

Female luna moths (actias luna) attract males by emitting chemical signals that spread through the air. a male hundreds of meters away can detect these molecules and fly toward their source. the sensory organs responsible for this behavior are the comblike antennae visible in the photograph shown here. each filament of an antenna is equipped with thousands of receptor cells that detect the sex attractant. based on what you learned in this chapter, propose a hypothesis to account for the ability of the male moth to detect a specific molecule in the presence of many other molecules in the air. what predictions does your hypothesis make? design an experiment to test one of these predictions.

The arrows in the illustration point to

Identify the area on the image where the force of attraction is the strongest.