How do tRNA molecules pick up amino acids in the cytoplasm?

Where do the amino acids come from?

Where do the amino acids come from that are picked up by tRNA molecules in the cytoplasm?

Answer:

Amino acids come from the food we eat and are broken down during digestion. They are picked up by tRNA molecules in the cytoplasm and transferred to the growing polypeptide chain in the ribosome, as part of the process of protein synthesis.

Amino acids in the cytoplasm are picked up by transfer RNA (tRNA) molecules. For a tRNA molecule to function, it must have its specific amino acid attached to it, this process is known as tRNA charging. Amino acids come from the foods we eat and during digestion proteins are broken down into amino acids. Those amino acids are then available in the cytoplasm for tRNA to pick up. Once an amino acid is attached to the tRNA molecule, it can recognize the codons on mRNA and match them with the correct amino acid. The tRNA can then transfer the amino acid to the growing polypeptide chain in the ribosome.

For example, a tRNA molecule that is responsible for the amino acid glycine will have a binding site at one end for glycine, and on the other end will contain an anticodon that matches the codon for glycine in the mRNA (the codon is GGA, so the tRNA anticodon would be CCU). This specific tRNA molecule can then 'read' its matched mRNA codon and bring over the glycine to the growing chain of polypeptides. This process is part of a larger procedure known as protein synthesis which also involves mRNA, ribosomes, and various enzymes, in which the genetic code is translated from RNA to proteins.