Answer:
the answer is cancle filter
Active transport requires energy from the cell. It occurs when substances move from areas of lower to higher concentration or when very large molecules are transported. Types of active transport include ion pumps, such as the sodium-potassium pump, and vesicle transport, which includes endocytosis and exocytosis.
A single molecule is the one that is responsible for initiating a signal transduction pathway. The answer in this question is a single molecule. Molecule is defined as an electrically neutral group of two atoms or more held together by a chemical bonds.