Why do cells need to be able to transport things across their membranes

Cell membranes are selectively permeable which means it allow certain molecules to move across it into and out of the cell. Cells need to be able to transport these substances to live and grow.

Transport of ions, water maintains the osmotic pressure of the cell. Transport of sugars like glucose is necessary to generate energy for the metabolic activities of the cell. Gases like CO2 are waste products of metabolic reaction which are removed by the cell through the cell membrane. Amino acids are required to make proteins.  

Transport across cell can occur through active and passive transport and transport of these substance are necessary for a cell to live and function properly.

americans began to notice growing differences between the northern and southern sections of the country. there were more people living in cities in the north, which made it more urban. more people lived on farms in the south, which made it more rural. while many people were farmers in the northern states, there were now other ways to make a living, such as working in mechanical cotton gins factories manufacturing cloth, tools and other goods. people in the north supported high tariffs on goods imported from europe because the extra cost encouraged people to “buy american” instead. in the southern states, planters did not like tariffs because they sold most of their production to europe and bought their tools from there as well. southerners believed the protective tariff was something that only northern factory owners keep their profits high. so the southern politicians came up with an idea. they would opt out. they would simply ignore the protective tariff. it was ‘null and void’ in south carolina. the state would not collect the taxes on goods imported into south carolina, no matter what the president said they had to do. this decision led to the nullification crisis.