Question

1.Describe one cases in which you know that is necessary the use of a symport to move molecules across the membrane. 2.Also describe the function of Na+ channels, K+ channels, and Ca+ channels in a neuron. Be specific on the type of channels that you describe.

Answer 1

1.To transport some substances against concentration gradient cells use energy already stored in ion gradients (H+ OR Na+ gradients) to power membrane proteins called transporters.In symport transported molecule and co transported ion move in the same direction.

consider an example

Step 1 - Amino aud Two substante bind to the extouullular side of transporter Nait touvelling down hill and eneegeze transport of amino aud Nat o 0 et Inside cell Extracellular Step 2: Transportes Chinges Concord orien - tation with respect to inner and outer Surface of memb Step 3 : After tounsport both substaatu are released

Transport of aminoacids across the intestinal liningin the human gut.

2.In neurons sodium channels are responsible for the rising phase of action potentials.The neuron cell membrane is partially permeable to sodium ions so sodium atoms slowly leak into the neuron through sodium leakage channels.The cell wants to maintain a negative resting membrane potential so it has a pump that pumps potassium back into the cell and pumps sodium out of the cell at the same time

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Negative cheese Not Not Nut Do do do Nat Nat no 11 Nat Nat Nat Depolarization - Influx of Nat - positive change Repolarization - Negative cheuge

calcium channels are the primary mediators of depolarization induced calcium entry into neurons.Calcium channels are of critical importance to brain function their dysfunction give rise to neurological disorders including pain,epilepsy,migraine and ataxia