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Cell Transport Essay

There are two types of cell transport mechanisms. These types of transports are passive and active transport. The difference between active and passive is that passive does not require energy and active does require energy. The reason passive does not require energy is because it travels down a concentration gradient. On a concentration gradient molecules naturally move from high to low concentration. In active transport, molecules move from low to high concentration. There are three different types of transports for passive and two types of transports for active.

The three types of passive transports are diffusion, osmosis, and facilitated diffusion. The two types of active transports are endocytosis, and exocytosis. Passive transport does not require ATP, also known as energy. The reason it does not require energy is because it travels down a concentration gradient. This means molecules naturally travel from high to low concentration. The first type of passive transport is diffusion. Diffusion is the movement of molecule across the membrane from high to low concentration. Diffusion naturally occurs until equilibrium is reached.

Only very small molecules can cross the membrane in diffusion. These include ions, gases, alcohols, and small lipids. The next type of passive transport is osmosis. Osmosis is the diffusion of water across the cell membrane. Three examples of osmosis are hypertonic, hypotonic, and isotonic solutions. A hypertonic solution is a solution that has a higher concentration of dissolved particles than another solution. A hypotonic solution is a solution that has lower concentration of dissolved particles compare to another solution.

Lastly an isotonic solution is a solution that has an equal concentration of dissolved particles compared to another solution. The last type of passive transport is facilitated diffusion. In facilitated diffusion molecules still move down a concentration gradient but they cannot pass the phospholipids on their own. Since they cannot cross on their own, they rely on proteins imbedded in the membrane to help them across. The two types of proteins that help them across are channel proteins and transport proteins also known as carrier proteins.

Active transport does require ATP, also known as energy. The reason it does not require energy is because it does not travel down a concentration gradient. It takes energy to go uphill and unlike passive transport in active transport, molecules move from areas of low concentration to areas of high concentration. Protein pumps move molecules into or out of the cell against the gradient. The two types of active transport are exocytosis and endocytosis. Endocytosis is moving molecules into cells.

The way molecules enter the cell is through a process. First molecules move into a pocket of the cell membrane. Next the pocket pinches off the membrane into cytoplasm. Lastly a vesicle is formed and can now move around inside the cell. The second type of cell transport, exocytosis, is the movement of molecules out of the cell. Exocytosis also goes through a process of moving out of the cell. First the vesicle pinches off the Golgi apparatus. Next the free vesicle migrates towards the cell membrane.

Third the vesicle contacts the cell membrane and begins to fuse with it. Lastly as the vesicle becomes part of the plasma membrane the contents spill out of the cell. Both endocytosis and exocytosis roughly occur at the same time and there is no overall change is the cell’s size. In conclusion there are two types of cell transport mechanisms. These include passive and active transport. The difference between passive and active transport is that active transport requires energy and passive transport does not.

The reason passive transport does not require energy is because in passive transport molecules travel down a concentration gradient. In a concentration gradient, molecules travel from an area of high concentration to an area of low concentration. In active transport molecules travel from an area of low concentration to an area of high concentration which is why it requires energy. In these two types of cell transport mechanisms there are five different types of transports. In all of these different kinds of transports, this is how the molecules move throughout the cell.


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