Secondary Active Transport
আমরা Primary active transport সম্পর্কে জানি যে এটা movement of substances across the cell membrane against chemical/electrical gradient with the active expenditure of energy deriving from ATP, by the help of carrier protein.
কিন্তু secondary active transport এ এনার্জি derived করে primary active transport এর concentration or electrical gradient থেকে। So,
▶️Definition: The movement of substances across the cell membrane
✅ against chemical or electrical gradient
✅ with the energy which is
✅ derived secondarily from concentration or electrical gradient produced by primary active transport,
✅ by the help of carrier protein is called secondary active transport.
▶️Types/subdivision: Two types-
1️⃣ Co-transport
2️⃣ Counter-transport
▶️ Movement occurs: Against concentration or electrical gradient
▶️ Energy requirement: Required
▶️ Presence of membrane: May or may not be present
▶️ Direction of movement: Can operate bi-directionally
▶️ Role of electrochemical gradient: Depends on them
▶️ Role of carrier protein: Doesn't give energy
1️⃣Co-transport: Secondary active transport of two substances in the same direction is called secondary active co-transport.
🌟Example:
🔘 Na+-Glucose co-transport: It is important in transporting glucose across renal and intestinal epithelial cells.
🔘 Na+-Amino acid co-transport: It also occurs through renal and intestinal epithelial cells to promote the absorption of these substances into the blood.
2️⃣Counter-transport: Secondary active transport of two substances in the opposite direction is called the secondary active counter-transport.
🌟Example:
🔘Na+-Ca2+ counter-transport: It occurs through almost all cell membranes where Na+ ions move interiorly and Ca2+ ions move exteriorly.
🔘Na+-H+ counter-transport: It occurs in several tissues where Na+ ions move interiorly and H+ ions move exteriorly.
⁉️ Co-transport and counter-transport are also called Symport and Antiport respectively.
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