Active Transport

define active transport

the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.

how are macromolecules and nutrients transported into and out of the cell?

they are transported by endocytosis and exocytosis.

what is the purpose of the sodium-potassium pump?

to maintain concentration differences. this protein transports Na+ ions and K+ ions up their concentration gradients.

what is transported by exocytosis?

to release large molecules such as proteins, waste products, or toxins that would damage the cell if they were released within the cytosol.

what is a cel membrane pump?

-these are the carrier proteins that serve in active transport. -they move substances from LOWER to HIGHER concentration.

explain how the sodium potassium pumps works

a number of three ions bind to the protein channel, and ATP is able to provide energy to change shape so ions are able to transport. one phosphate group stays with the ATP, bounding with the channel. then on the other side, sodium ions are released outside of the cell and then the new shape causes hih amounts of potassium ions, then two of the ions now are able to bond to the channel.

what is endocytosis?

cells ingest external fluid, macromolecules, and large particles, including other cells.

compare and contrast the carrier proteins used in facilitated diffusion those used in active transport.

in both, the molecules first binds to a specific kind of carrier protein on one side of the cell membrane. once it is bound to the molecules, the protein changes shape, shielding the molecules from the hydrophobic interior of the phospholipid bilayer. -the protein then transports the molecule through the membrane and releases it on the other side. however, cell membrane pumps require energy. most often the energy needed for active transport is supplied directly or indirectly by ATP.

what are two main types of endocytosis? how do they differ?

pinocytosis- involves the transport of solutes or fluids. phagocytosis- is the movement of large particles or whole cells. - many unicellular organisms feed by phagocytosis. in addition, certain cells in animals use phagocytosis to ingest bacteria and viruses that invade the body.

what is exocytosis?

the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.