active + co-transport

i dont like epithelial cells

what is active transport?

the movement of a substrate from a low concentration too a high concentration using metabolic energy in the form of ATP and a carrier protein

describe the process of active transport:

• involves carrier proteins spanning cell membrane

• molecule binds to a complementary receptor

• ATP binds to the carrier protein from the inside of the cell and is hydrolysed into ADP and Pi

• this causes a conformational change in the carrier protein, allowing the molecule to be released on the other side of the membrane

• Pi is released and protein returns to original shape (ADP and Pi later reform ATP in respiration)

what is co-transport?

type of active transport where the transport of one substance is coupled with the transport of another substance across a membrane w/ a carrier protein and metabolic energy in the form of ATP

describe the role of co-transport in the ileum:

how glucose/AAs are absorbed from ileum into bloodstream:

• Na⁺ ions are actively transported out of the epithelial cell into the blood

• this lowers the conc of Na⁺ ions in the epithelial cell, creating a conc gradient of Na⁺ ions

• Na⁺ and glucose bind to a cotransporter protein and enter the cell by facilitated protein and enter cell by facilitated diffusion/co-transport (respectively)

• there is now a higher conc of glucose inside the epithelial cell than the blood

• glucose moves from cell to blood by facilitated diffusion

• (there is no glucose buildup in the blood as the blood flows and carries away absorbed glucose)