welcome to moomoomath and science the cell theory states that cells are alive if you watch these single cell organisms you can see that they are alive in order to stay alive and maintain homeostasis cells must move objects in and out of the cell a very simple method of moving objects in and out like oxygen and carbon dioxide is diffusion a simplistic way to understand diffusion is high to low is the only way to go particles will move from an area of high concentration to an area of low concentration some objects can easily pass through the cell membrane which is a phospholipid bilayer it is composed of two layers remember bi means two and the phosphor lipids have a polar head and a non-polar tail particles moving with diffusion move with the concentration gradient or in other words from high to low this type of movement does not require energy from the cell however there are other methods of passive transport called facilitated diffusion with facilitated diffusion a channel or protein is used to help move the particles in and out of the cell for example glucose will move from an area of high concentration to low concentration but will need a protein a carrier protein to move into and out of the cell these carrier proteins do not require atp and move objects into and out of the cell using diffusion however sometimes these objects are either too large or need to go against the concentration gradient active transport comes to the rescue however active transport requires energy in the form of atp to move these objects in and out let's take a look at three types of active transport membrane pumps endocytosis and exocytosis a membrane pump moves substances against the concentration gradient or from a low concentration to a high concentration a good example is the sodium potassium pump three sodium ions attach the carrier protein atp attaches a phosphate to the carrier protein and it changes its shape this allows three sodium ions to leave the cell and then two potassium ions now attach to the carry protein the phosphate detaches from the protein and it changes shape once again and the potassium now travels into the cell this allows sodium and potassium to go against the concentration gradient the cell also uses two types of vesicle movement endocytosis and exocytosis endocytosis allows the cell to move larger objects into the cell by engulfing the object and then moving this object into the cell there are three types of endocytosis phagocytosis which is when a cell moves in solids pinocytosis which is when a cell moves in liquids and receptor medial mediated endocytosis which is a form of endocytosis in which receptor proteins on the cell surface capture a specific target molecule when the receptors bind to their molecule endocytosis is triggered and the receptors and their attached molecules are taken into the cell in a vesicle exocytosis occurs when the cell expels an object out of the cell objects inside the cell are encased in a vesicle which is expelled if you'd like to know more about active transport this playlist will help and as always thanks for watching and moving math uploads a new map and science video