A protein is a long chain of amino acids, connected by a peptide bond. Amino acids are the essential building blocks, some of which the body can synthesise by itself and others which have to come from our diet. Proteins are made by ribosomes, which translate DNA (via RNA) into an amino acid sequence. tRNA brings the amino acids to the ribsome, while mRNA tells the ribosome which order to connect them in, forming a long, snake-like protein.
I would use the whiteboard to draw out a peptide bond, and link the student to the following 3 minute video made by Harvard Department of Cell Biology: https://www.youtube.com/watch?v=TfYf_rPWUdY