Sodium and potassium ion channels have several negatively charged residues at the entry to the channel. On what basis do K+ channels specifically select for K+ ions? (In other words, why dont K+ channels enable Na+ ions to cross the membrane?)

A. ionic radius, Na+ is to small
B. energy cost, it is to energetically costly to dehydrate Na+
C. charge, Na is slightly more electronegative than K and does not interact with the channel carbonyl groups
D. charge, Na is slightly less electronegative than K and does not interact with the channel carbonyl groups
E. ionic radius, Na+ is too big

metamorphism is the change of minerals or geologic texture (distinct arrangement of minerals) in pre-existing rocks (protoliths), without the protolith melting into liquid magma (a solid-state change). the change occurs primarily due to heat, pressure, and the introduction of chemically active fluids. i hoped i !

digestion

it excretes wastes

weathering - colorado river carves land in arizona to form the grand canyon. cracks form in a sandstone wall surrounding a house. a marble statue near the science museum is changing color due to rainfall

erosion - after a rainstorm, soil and rock piees litter the roadways. the sand dunes in the sahara desert are changing shape.

here's your answer.

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