Hey there!
The purpose of guard cells is to control the opening and closing of the Stomata, keeping it the correct width, or size.
Therefore, your correct answer would be Option 3, control the size of the Stomata.
Hope this helps!
um i believe its the skin cell?
All the options are incorrect. The correct answer will be THE NUMBER OF HYDROGEN IONS MOVING DOWN THE PROTEIN CHANNEL.
A proton pump is found in the inner membrane of mitochondria which is also known as hydrogen ion pump. The hydrogen ion is pumped across the inner mitochondrial membrane depending on the proton gradient.