Question

1. Summarize and explain the mechanism of (1)ATP-powered pump, (2)ion channel and (3)transporter including uniporter, symporter and antiporter

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Answer 1

1) ATP POWER PUMP - they couple the splitting or hydrolysis of atp witht the movement of ions across the membrane and thats too against the concentration gradient. in these pumps, the atp is hydrolysed into adp and inorganic phosphate , and the energy released is used to move one or more ions across the cell membrane. around 25percent of cell's atp reserve are spent in such ion transport,ex - NA+-k+ ATPase pump, in which na+ out of the cell while the k+pumps into the cell

2)ION CHANNEL - these are the protein molecules that span across the cell membrane allowing the passage of ions from one side of the molecule to the other. they have an aqueous pore which is accessible to ions after conformational change in the protein structure that cause the ion channel to open.the primary role of ion channel is to regulate the passage of ions across themembrane, and the alteration if intra cellular ion concentration as the primary signalling mechanism of ion channels. few types of ion channel - L type, cGMP gated, cacium activated and others

3)

i) UNIPORT - facilitated diffusion and work by binding to one molecule of the substrate at a time to move along its concentration gradient.

ii) ANTIPORTS - transport molecule in opposite directions

iii) SYMPORTS - transport molecule in the same direction across the membrane