Define target cell and explain why all cells are not target cells for all hormones

The target cell is specific, it means that they are specific to their hormone. For every hormone target cell is different because every cell is very specific to their particular site. Hence, the receiver and pocket should be unique. So this is the target cell. Every cell doesn't need the effect of every hormone. So, all the cells do not target cells for all the hormone because not every cell have specific receptor.

regulation of gene expression. gene expression can be regulated by various cellular processes with the aim to control the amount and nature of the expressed genes. these regulatory proteins bind to dna and send signals that indirectly control the rate of gene expression

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