Exam 3- Active Transport Flashcards
What is active transport?
the cell must use energy from one reaction to drive the unfavorable reaction of molecules against this [gradient]
How does the Na-K pump work?
1.Pump is in a conformation that allows exposure of the cavity inside the pump and high affinity binding sites for Na to the intracellular environment and Na ions bind to these binding sites.
2.Pump is phosphorylated by a cellular kinase
• Involves use of ATP
• Cavity exposed to extracellular environment
• Changes affinity of binding sites for Na, releasing Na ions to the outside of the cell.
3.Upon release of Na+ ions, 2 high affinity binding sites for K+ are exposed (K+ ions bind to these binding sites)
• Leads to de-phosphorylation of the pump
4.De-phosphorylation of the pump triggers a conformational change of the pump, exposing cavity to intracellular environment.
• Changes affinity of binding sites for K+, releasing K- ions to the inside of the cell
How many ions are exchanged with the Na-K pump?
3Na+ out and 2K+ in
What’s Osmotic Pressure?
The pressure that needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.
Knowing that the cell contains a very high concentration of macromolecules, which are present at a much lower concentration in the extracellular environment, how does the cell prevent water from continuously pour into it?
Potassium has a much lower concentration in the extracellular environment; the high organic compound concentration inside the cell allows water to come in when needed to balance concentration gradients (osmotic pressure)
