active transport occurs in the membrane at proximal tubule.
active transport occurs in the membrane at proximal tubule.
where does active transport occur in the membrane?
proximal tubule
Na
Na
specialized transmembrane proteins recognize the substance and allow it to move across the membrane when it otherwise would not, either because the phospholipid bilayer of the membrane is impermeable to the substance moved or because the substance is moved against the direction of its concentration gradient. there are two forms of active transport, primary active transport and secondary active transport. in primary active transport, the proteins involved are pumps that normally use chemical energy in the form of atp. secondary active transport, however, makes use of potential energy, which is usually derived through exploitation of an electrochemical gradient. the energy created from one ion moving down its electrochemical gradient is used to power the transport of another ion moving against its electrochemical gradient. this involves pore-forming proteins that form channels across the cell membrane. the difference between passive transport and active transport is that the active transport requires energy, and moves substances against their respective concentration gradient, whereas passive transport requires no energy and moves substances in the direction of their respective concentration gradient.
active transport