Protein Synthesis Degradation and Secretion

I. Table 5-1 summarizes the steps leading from DNA to protein synthesis.

II. Transcription involves the formation of a primary RNA transcript by base-pairing with the template strand of DNA containing a single gene and the removal of intron-derived segments by spliceosomes to form mRNA, which moves to the cytoplasm.

III. Translation of mRNA occurs on the ribosomes in the cytoplasm by base-pairing between the anticodons in tRNAs linked to single amino acids, with the corresponding codons in mRNA.

IV. Chaperones help fold large proteins into their proper conformation as they are released from ribosomes.

V. Protein transcription factors activate or repress the transcription of specific genes by binding to regions of DNA that interact with the promoter region of a gene.

VI. The concentration of a particular protein in a cell depends on: (1) the rate of its gene's transcription, (2) the rate of initiating protein assembly on a ribosome, (3) the rate at which mRNA is degraded, (4) the rate of protein digestion by enzymes associated with proteosomes, and (5) the rate of secretion, if any, of the protein from the cell. VII. Proteins secreted by cells pass through the sequence of steps illustrated in Figure 5-10. Targeting of a protein to the secretory pathway depends on the signal sequence of amino acids that first emerge from a ribosome during synthesis.

Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition

Genetic Information and Protein Synthesis CHAPTER FIVE

Genetic Information and Protein Synthesis CHAPTER FIVE

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