G is enhanced by the presence of cholesterol. is decreased when the proportion of unsaturated fatty acids is increased. describes the movement of water within the membrane double layer. increases with increasing temperature. is usually higher in plant cell membranes than animal cell membranes.

he is very short, and he can only reach halfway up on the elevator buttons. but on a rainy day, he has his umbrella with him, and he uses it to poke the button at the top.

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.