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3.5 distinguish between active and passive transport and relate these to processes occurring in the mammalian kidney
distinguish between active and passive transport and relate these to processes occurring in the mammalian kidney
- Active transport involves an expenditure of energy on the part of the organism, usually because the substance is moving against the concentration gradient, i.e. when a salt moves to an area of high salt concentration from an area of low salt concentration. Passive transport involves no expenditure of energy as the materials follow the natural concentration gradient, i.e. movement from an area of high concentration to an area of low concentration. Both diffusion and osmosis are examples of passive transport.
- In the mammalian kidney, both active and passive transport processes occur.
- Passive transport: Once filtration has occurred in Bowman’s capsule, water returns via the interstitial fluid from the tubule to the capillary in the process of osmosis. This occurs along the length of the tubule.
- Active transport: Depending on their concentration, the ions in the blood (Na+, K+, Cl- , H+ and HCO3) can be transported to cells in the nephron tubule and then secreted by the cells into the tubule. Some poisons and certain drugs are eliminated from the body in this manner.