: Energy is consumed directly at the site of transport to create a "pressure" (a concentration gradient) outside the city. 2. Secondary Active Transport: The Clever Hitchhiker
Na+/K+cap N a raised to the positive power / cap K raised to the positive power secondary active transport vs primary
) ions, but the crane’s job is to push even more of them outside into the "Salty Sea." This is an uphill battle because it goes against the natural flow—like trying to push water back up a waterfall. : Energy is consumed directly at the site
There are two types of secondary transport: There are two types of secondary transport: |
| Feature | Primary Active Transport | Secondary Active Transport | |---------|--------------------------|----------------------------| | | ATP hydrolysis | Electrochemical gradient (e.g., Na⁺ or H⁺ gradient) | | Indirect energy source | None (direct use of ATP) | ATP (used earlier to create the gradient) | | ATP consumption | Yes, during transport | No, not during transport (but used to set up gradient) | | Typical cargo | Ions (Na⁺, K⁺, Ca²⁺, H⁺) | Small molecules (glucose, amino acids), ions | | Key protein | ATPase pump (e.g., Na⁺/K⁺ ATPase) | Cotransporter (symporter or antiporter) | | Can it create a gradient? | Yes – it establishes the initial gradient. | No – it uses an existing gradient. |