Tha main components in blood are the plasma, red blood cells, white blood cells, and blood platelets.
Plasma is like the main component that makes up most of the blood. It has a light yellow color and it carries many substances including nutrients, waste, hormones and more.
Red blood cells are the reason why blood is red in color. They have a hemoglobin inside them which can help carry oxygen for the tissues and organs. In order to maximize the oxygen carrying capacity, they don't have a nucleus.
White blood cells can be divided into phagocytes and lymphocytes. Their main function is to protect us from diseases. Phahocytes and engulf and digest bacteria, while lymphocytes can produce antibodies.
Blood platelets can cause blood clotting which can stop us from bleeding forever. They're not cells, but just fragments of cells. They also don't have nucleus since they're not complete cells.
Endocytosis is a term used to describe a process of active transport that facilitates the movement of particles such as molecules and parts of a cell or the whole cell into a cell.The best scenario for the process occurs when a cell needs to pass/transport molecules that are large and cannot move through the membrane passively.