1. Translation Translation is the process of building a protein from the mRNA transcript. The protein is built as transfer RNA (tRNA) bring amino acids (AA), one at a time, to the ribosomal unit holding the mRNA.

2. tRNA 3D structure has an attachment site for an AA on one side and the anticodon on the other – anticodon is the complimentary sequence to the mRNA codon if the mRNA is AUG the tRNA is UAC the AA attached is Met (methionine) – is "L" shaped with an attachment site for an AA and a loop on the other side that carries the anticodon each tRNA is specific for the AA it attaches to tRNA are always present in the cytoplasm

3. tRNA are joined to the correct AA by the an enzyme (tRNA synthetase ) – each tRNA fits ONLY the and AA it is specific for Lock –n- key – 20 different versions in the cytoplasm at all times – catalyzes the attachment of the AA to the tRNA with the use of ATP the activated tRNA delivers its AA to the growing polypeptide chain

4. Ribosomes Ribosomes facilitate the binding of the tRNA to the mRNA by aligning the active sites and holding them in place. Structure – ribosomes are made of mostly ribosomal RNA (rRNA) that is made from DNA that resides in the nucleolus – consists of a large unit and a small unit once assembled the 2 units are exported to the cytoplasm via membrane pores in the nuclear envelope – has 3 binding sites A - site binds next tRNA with AA atached P - site binds the tRNA whose AA is being attached to the growing chain E - site binds the leaving tRNA minus the AA

5. Initiation of translation Small ribosomal subunit binds with the mRNA and searches for the start codon (AUG) – union of the mRNA & tRNA at the P- site establishing the reading frame large unit attaches after the union is made completing the initiation complex - translation begins – proteins called initiation factors bring the units together

6. Elongation of Growing Polypeptide – mRNA moves from 5' to 3' – elongation ends when a stop is reached - UAG, UAA, UGA does not code for an AA but binds to a release factor that causes the the ribosomal unit comes apart – may be translated by many ribosomes at the same time - ployribosomal unit

7. Post Translation Modifications proteins begin to spontaneously fold as they are synthesized – some will require additional proteins (chaperonins) free ribosomes make proteins destined for the cytosol bound ribosomes make proteins for the membrane systems of the cell – ALL start as free ribosomes and bind to the ER if a signal peptide is present