BIOB34H3 Lecture Notes - Lecture 8: Homeostasis, Hydrophile, Cytoskeleton
30 Sep 2016
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In the absence of energy, molecules always go down their electrochemical gradient until equilibrium is reached (maximum entropy) Differentiate primary active transport from secondary active transport. *** it is very important to understand: homeostasis (consistent internal environment with changes in external environment) is not equivalent to equilibrium. To maintain salt homeostasis in their body, fish that live in salt water must use energy to avoid equilibrium. There are 2 ways for animals to prevent equilibrium being reached. Selective permeability only allowing certain molecules to past a boarder(cellular membrane or epithelia) Most molecules cannot pass through the lipid bilayer of cell membranes (nothing with charge) Thus, cell membranes are selectively permeable only permeable to non polar hydrophobic molecules. Specialized proteins called channels and transporters embedded in the membrane are what determine what molecules can pass through. Channels are proteins with structures that open holes in the membrane for specific molecules to pass through by diffusion.
