Protein synthesis Translation

Things to know… Structure and function of tRNA Structure and function of ribosome Stages of translation Initiation Elongation Termination Types of RNA Mutations can change products

Figure 17.12 Translation: the basic concept

Figure 17.13a The structure of transfer RNA (tRNA)

Figure 17.13b The structure of transfer RNA (tRNA)

Figure 17.4 The dictionary of the genetic code

Figure 17.5 A tobacco plant expressing a firefly gene

Figure 17.14 An aminoacyl-tRNA synthetase joins a specific amino acid to a tRNA

Figure 17.15 The anatomy of a functioning ribosome

Figure 17.17 The initiation of translation

Figure 17.18 The elongation cycle of translation

Figure 17.19 The termination of translation

Figure 17.20 Polyribosomes

DO NOW: on small paper Identify the difference(s) between ribosomes in cytoplasm and on ER. Can cytoplasmic and ER ribosomes ever change places? If so, when?

ER Protein Targeting Ribosomes begin translating; if first stretch of polypeptide bears a particular sequence (signal polypeptide), it attracts an SRP and moves to an SRP receptor protein in ER membrane. Polypeptide feeds into cisternal space, signal peptide is removed and degrades and ribosome dissociates. Protein remains in ER membrane, routed to Golgi for further processing, etc. Other signal peptides probably target mitochondria, chloroplasts, etc.

Table 17.1 Types of RNA in a Eukaryotic Cell

Figure 17.22 Coupled transcription and translation in bacteria

Figure 17.23 The molecular basis of sickle-cell disease: a point mutation

Figure 17.24 Categories and consequences of point mutations: Base-pair insertion or deletion

Figure 17.24 Categories and consequences of point mutations: Base-pair substitution

Figure 17.25 A summary of transcription and translation in a eukaryotic cell