Outside of the U.S., many cruise lines do not have automatic tipping policies, says McDaniel, as other countriesâ tipping customs are different than ours (and thus their staff is paid differently), so it may pay to look at cruises leaving from other countries and then look at their âsuggestedâ tipping options.
Best Answer: Active transport is the mediated process of moving particles across a biological membrane against a concentration gradient. If the process uses chemical energy, such as from adenosine triphosphate (ATP), it is termed primary active transport. Secondary active transport involves the use of an electrochemical gradient.
All cells are enclosed with a cell membrane. A selectively permeable cell membrane is one that allows certain molecules or ions to pass through it by means of active or passive transport.Active transport processes require the cell to expend energy to move the materials, while passive transport can be done without using cellular energy.he method used by a cell to pass molecules in or out is determined by the size of the molecule, as well as the concentration of the molecules on the inside and outside of the cell. Most cell membranes are covered with tiny protein channels that allow things to move in and out of the cell.