2026-08-17 13:56:29: Mechanisms of Transportation

biology/Cell Structure and Function/Mechanisms of Transport.md

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+[[Cell Structure and Function]]
+
+Mechanisms of active transport.
+
+# Summary
+* Active transport moves substances against their concentration gradient and requires energy, usually from ATP hydrolysis
+* Membrane proteins (pumps) required for active transport. Bind to molecules and moves them.
+* Na+/K+ pump (sodium potassium pump) moves 3 Na+ out and 2K+ in per ATP. Builds chemical and electric gradients.
+* Unequal ion movement contribute to membrane potential, helping cell's separation of charges.
+* Gradients store potential energy.
+* Passive transport requires no energy and moves substances down the gradient.
+
+# Why ATP Is Required
+Requires metabolic energy. Uses hydrolysis to break ATP (adenosine triphosphate) ADP and inorganic phosphate (Pi), which releases energy that membrane proteins require. When ATP runs out, active transport stops.
+# The Role of Membrane Proteins
+Specialized membrane proteins:
+* Act as pumps
+* Undergo conformational changes using the ATP hydrolysis energy
+* Selective for which molecules they bind to
+* Moves substances across the membrane
+
+# The Sodium-Potassium Pump: The Key Example
+Na+/K+-ATPase is a transmembrane protein that:
+* Runs continuously to maintain ion concentrations, since ions tend to equalize
+* Acts as an ATPase enzyme, catalyzing the ATP hydrolysis
+* Transports 3 Na+ out and 2K+ in per ATP
+* Uses released energy to pump ions against gradient
+Sodium potassium pumps use gradients that combine chemical and electric gradients.
+
+Chemical Gradient:
+* Keeps Na concentration higher outside cell
+* Keeps K concentration higher inside cell
+* Stores potential energy
+
+Electrical Gradient:
+* Because 3 positive ion leave for every 2 that enter, net loss of charge, making interior more negative
+* Contributes to resting membrane potential
+* Helps support nerve impulse transmission, muscle activity, nutrient uptake,