Cell transport processes

  Created March 2020, Offline version here
  Video by Paul Anderson, also on his website Bozeman Science.



    Cellular transport refers to the transport of substances or materials across a membrane. The plasma membrane is said to be semi-permeable as it is selective in what can enter or exit the cell; not everything can access the cell. There are two general types of transport: passive and active transport. Passive transport energy while active transport energy. The type of energy molecule that cells use for all process that require energy is called
    In simple diffusion, molecules of a certain substance can travel through the semi-permeable plasma membrane. One specific type of diffusion is called osmosis where it refers to the movement of
    Unlike simple diffusion, in facilitated diffusion, substances need to travel through a
    This is because some substances are too large to diffuse through and it also might be or charged. One example of a substance that requires facilitated diffusion for transport is glucose. The other general form of transport is called active transport and it requires
    Unlike passive transport, active transport moves substances from an area of concentration to an area of concentration.
    There are two main forms of active transport. One that uses protein pumps and the other is used to transport massive quantities of substances. The most widely known protein pump is called the sodium-potassium ion pump. For every energy molecule of , there is an exchange of three sodium ions and two potassium ions. For the sodium-potassium pump to function, it needs one from ATP to bond with the protein. From there, the attached phosphate will cause a change which is just the protein changing its shape. By changing the shape of the protein, it will allow sodium or potassium ion to enter the protein. When another phosphate from another ATP attaches to the protein again, the protein will change its shape, releasing the contents to the other side. An example of where sodium-potassium pumps are found are located in the brain. The neuron needs to maintain a negative charge for the resting action potential. Since sodium and potassium ions are positively charged, the ion pumps help regulate the overall charge of the neuron. The other types of active transport refer to the movement of large quantities of substances. One type is called where the cell transports material out of the cell using vesicles. The other type is called where the cell intakes large particles into the cell. One example in the human body where exocytosis occurs is in the neurons. Neurons use exocytosis to large amounts of chemicals called neurotransmitters. An example of endocytosis is when a phagocyte, a type of white blood cell, or engulfs foreign bodies in the blood stream. In summary, passive transport does not require energy and has several types: simple diffusion, facilitated diffusion, and osmosis. Osmosis only refers to the movement of water. Active transport requires energy and two forms are: one that uses protein pumps and the other is endocytosis/exocytosis where large quantities of substances are transported. Endocytosis take in material and exocytosis release material.