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6 Cards in this Set
- Front
- Back
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How active transport differs from facilitated diffusion |
• uses ATP (requires energy) • against a concentration gradient (low to high) • uses only carrier proteins |
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Diffusion (passive) |
Net movement of molecules down a concentration gradient (high to low) |
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Factors affecting diffusion |
• Contraction gradient • area over which diffusion takes place • thickness of exchange surface |
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Other factors affecting diffusion |
• nature of plasma membrane - number of pores • size and nature of diffusing molecules - smaller molecules diffuse faster - fat soluble molecules diffuse faster - polar molecules diffuse faster than non polar |
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Osmosis |
Movement of water from high to low through water soluble channels |
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Active transport in absorption |
• sodium ions actively transported out of epithelial cells by sodium-potassium pump into blood • higher concentration of sodium ions in lumen than inside epithelial cells • sodium ions diffuse into epithelial cell down their concentration through co-transport protein in cell surface membrane • when sodium ions flood in glucose molecules follow • glucose passes into blood plasma by facilitated diffusion using another carrier |
