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