Active transport requires energy (ATP) and moves substances against their concentration gradient (from low to high concentration). Sodium-potassium pump pumps three sodiums ions out and two potassium ions in the cell using ATP in a 4-step process. 1) Three sodium ions inside the cell attach to the pump and ATP releases phosphate on the pump. 2) The three sodium ions are transferred out of the cell when the shape of the pump changes. 3) Two potassium ions inside he cell attach to the pump and are released inside of the cell when the pump changes its shape. 4) phosphate group is released, 2 potassium ions are released inside the cell. The sodium-potassium pump is important for our body because it prevents sodium to pile up in a cell, keeps the water to not accumulate in the cell (by osmosis), and it helps transport other substances across the membrance (like glucose).
“Vesicles move substances across the membrane.” Endocytosis makes vesicles filled with substances because it brings in larger substances from the outside of the cell to the inside the membrane. Exocytosis releases substances from the inside of the cell membrane to the outside of the cell, it releases its contents as well.
The membrane receptor proteins receive information and attach to certain signal molecules allowing the cell to respond to the signal. Signal molecules change the behavior of the receiving cell by changing in permeability of the membrane, changing the formation of second messengers inside, and activation enzymes inside. The change in permeability of the membrane can be seen with an ion channel. An ion channel is usually closed and no ions can cross the channel. ‘But when the signal molecule binds to the receptor protein, it opens the ion channel gate and allows ions through the ion channel. The formation of the second messengers inside are triggered when the signal molecules bind to the receptor protein which reacts an intermediary protein which activates an enzyme and the enzyme catalyzes the formation of the second messenger. ‘ Drugs can affect this the attraction between signal molecules and receptor proteins.
Enzymes causes something to happen. Liver has a job for storing food as glycogen (a bunch of glucose stuck together) Pancreas uses the blood vessels to send a message and the receptor protein takes that messenger and turns it into the glycogen.