BIOMOLECULES AND ENZYMES

Detailed explanation-1: -The tRNA that has given up its amino acid is released. It can then bind to another molecule of the amino acid and be used again later in the protein-making process. Using a ratcheting mechanism, the ribosome advances the mRNA, three nucleotides at a time.

Detailed explanation-2: -During protein synthesis, mRNA and tRNAs are moved through the ribosome by the dynamic process of translocation. Sequential movement of tRNAs from the A (aminoacyl) site to the P (peptidyl) site to the E (exit) site is coupled with movement of their associated codons in the mRNA.

Detailed explanation-3: -The A site accepts an incoming tRNA bound to an amino acid. The P site holds a tRNA that carries a growing polypeptide (the first amino acid added is methionine (Met)). The E site is where a tRNA goes after it is empty, meaning that it has transferred its polypeptide to another tRNA (which now occupies the P site).

Detailed explanation-4: -Amino acids are attached to tRNAs at the 3′-terminal adenosine at the end of a CCA trinucleotide sequence that is common to all tRNAs. In the second domain is a trinucleotide sequence known as the anticodon, located ∼75 Å from the amino acid attachment site.