Answer:
Sometimes molecules cannot move through the cell membrane on their own. These molecules need special transport proteins to help them move across the membrane. Facilitated diffusion is the diffusion of substances with the help of transport proteins in the plasma membrane. These special proteins are called channel proteins or carrier proteins, and they are attached to the cell membrane. In fact, they go through the cell membrane, from the inside of the cell to the outside. Facilitated diffusion is used for molecules that cannot diffuse rapidly through cell membranes on their own, even when the molecules are moving from high to low concentration areas. An example is the sugar plants and animals use for energy, called glucose. Even though facilitated diffusion involves transport proteins, it is still passive transport because the solute is moving down the concentration gradient so it does not require the use of cellular energy.
cause an increase in the rate of certain mutations
The answer is a simple radial nervous system.
Echinoderms do not have brains. Around their mouth, they have central rings from which nerves radially run into arms and along the body. Movement is controlled by the branches of those radial nerves.
A stationary front is the least likely to be associated with rainfall.
Cell division. The whole process involves 3 main stages namely interphase, mitosis and cytokinesis.It would, however be wrong to say that its mitosis only because mitosis does not involve the duplication of chromosomes. Duplication of chromosomes occur during the interphase while the splitting of cells occur during Telophase of mitosis and Cytokinesis. Therefore, answer to this has to be generalised to be just cell division.
