BI110 Lecture Notes - Lecture 16: Clathrin, Cytoplasm, Endocytosis
Document Summary
Bi110-lecture 16-membrane transport (module 18 cont"d) & exocytosis and endocytosis (module 19) Requires a direct or indirect input of energy derived from atp hydrolysis. Energy required to move against the concentration gradients. Depends on specific membrane transport proteins, which can be soluble. The same protein that transports substance also hydrolyzes atp to power to transport directly. Transport proteins do not break down atp, but instead, use a favourable concentration gradient of substance as their energy source. Moves positively-charged ions across the membrane cells lining stomach. Na+/k+ pump: maintains low intracellular calcium ion concentration pumps out 3 na+, and pumps in 2 k+ in every cycle; Creates negative membrane potential to transport the electrochemical gradient across the membrane. Essential for active transport in all animal cells (but not in plant cells or most microbes) Process of the na+/k+ (sodium-potassium) pump (see diagram below): 3 sodium ions bind to the cytoplasmic side of the pump.
