7.3 Translation

IB Syllabus Statements

Understandings:

Initiation of translation involves assembly of the components that carry out the process.
Synthesis of the polypeptide involves a repeated cycle of events.
Disassembly of the components follows termination of translation.
Free ribosomes synthesize proteins for use primarily within the cell.
Bound ribosomes synthesize proteins primarily for secretion or for use in lysosomes.
Translation can occur immediately after transcription in prokaryotes due to the absence of a nuclear membrane.
The sequence and number of amino acids in the polypeptide is the primary structure.
The secondary structure is the formation of alpha helices and beta pleated sheets stabilized by hydrogen bonding.
The tertiary structure is the further folding of the polypeptide stabilized by interactions between R groups.
The quaternary structure exists in proteins with more than one polypeptide chain.

Application and skills:

Application: tRNA-activating enzymes illustrate enzyme–substrate specificity and the role of phosphorylation.
Skill: Identification of polysomes in electron micrographs of prokaryotes and eukaryotes.
Skill: The use of molecular visualization software to analyse the structure of eukaryotic ribosomes and a tRNA molecule.

Explain the process of ‘initiation’ in translation.
Explain the repeated cycle of events that happens during synthesis of a polypeptide.
Explain the events during termination of translation including the disassembly of the components.
Outline the names of the tRNA binding sites as well as their roles.
Distinguish between free and bound ribosomes including the role of lysosomes.
Explain why translation can occur immediately after transcription in prokaryotes.
Outline what is meant by the primary structure of polypeptides.
Explain the structures that help to maintain the secondary structure of polypeptides.
Explain how the tertiary structure of polypeptides is maintained, including the relevant interactions between R groups.
Explain why polar and non-polar amino acids are relevant to understanding the bonds formed between R groups in the tertiary structure of proteins.
Outline the quaternary structure in proteins, including a well-known example. Discuss what is meant by a ‘prosthetic group’ and a ‘conjugated protein’ to help in understanding the quaternary structure of proteins.
Explain how tRNA-activating enzymes illustrate enzyme-substrate specificity and the role of phosphorylation.
Explain how you identify polysomes in electron micrographs.
Explain how molecular visualization software can be used to analyze the structure of eukaryotic ribosomes and tRNA molecules. What purpose could this serve?