what is the structure of tRNA?  

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Remember that all RNA is made of RNA nucleotides with the bases A, G, C, and U, connected by the 3' sugar of one nucleotide joined to the 5' phosphate of the next nucleotide.  tRNA, like other RNA's, is a single strand of RNA nucleotides. It gets twisted up into a multi-looped shape with a couple significant parts, held in this "cloverleaf" shape by H-bonds between bases. One is the 3 bases of the anti-codon that matches up to the codon on mRNA. The other is the CCA 3' end where the amino acid specific to that tRNA is attached.