PROTEIN SYNTHESIS Section 12 3 How your cell

PROTEIN SYNTHESIS Section 12. 3

How your cell makes (“synthesizes”) proteins • General steps: DNA RNA Protein • Occurs in 2 phases: phases 1. Transcription (DNA RNA) – occurs in the nucleus 2. Translation (RNA Protein) – occurs on the ribosome in the cytoplasm

DNA RNA Protein

RNA is DIFFERENT from DNA 1. RNA has a sugar ribose DNA has a sugar deoxyribose 2. RNA contains uracil (U) DNA has thymine (T) 3. RNA molecule is single-stranded DNA is double-stranded

3 types of RNA A. messenger RNA (m. RNA) B. transfer RNA (t. RNA) C. ribosomal RNA (r. RNA)

m. RNA – the “Messenger” • Carries instructions from DNA to the ribosome. • Gives the ribosome the “recipe” for making a specific protein

r. RNA • Part of the structure of a ribosome • Helps in protein production t. RNA “go-getter” Gets the right parts (amino acids) to make the right protein according to m. RNA instructions

Phase 1: Transcription • m. RNA is produced by copying part of DNA into a complementary sequence of RNA • Occurs inside the nucleus because DNA CANNOT leave the nucleus

Question: • What would be the complementary RNA strand for the following DNA sequence? GCG TAT

ANSWER: • DNA: GCG TAT • RNA: CGC AUA

CODONS • Bases are read in groups of 3, called codons. • Each codon stands for 1 amino acid.

DNA: TAC CTT GTG CAT GGG ATC m. RNA AUG GAA CAC GUA CCC UAG A. A MET G. A HIS VAL PRO STOP

Another RNA Chart

PHASE 2: Translation - making proteins -m. RNA lays across the ribosome -bases are read one CODON (3 bases) at a time -t. RNA molecules with complementary ANTICODONS deliver the appropriate amino acid to the ribosome -amino acids are linked together in a long chain to form a protein (“polypeptide”

PHASE 2: Translation - making proteins 3 Steps: 1. Initiation 2. Elongation 3. Termination

Translation

Initiation aa 1 1 -t. RNA anticodon hydrogen bonds U A C A U G codon aa 2 2 -t. RNA G A U C U A C U U C G A m. RNA

Elongation peptide bond aa 3 aa 1 aa 2 3 -t. RNA 1 -t. RNA anticodon hydrogen bonds U A C A U G codon 2 -t. RNA G A U C U A C U U C G A m. RNA

aa 1 peptide bond aa 3 aa 2 1 -t. RNA 3 -t. RNA U A C (leaves) 2 -t. RNA A U G G A A G A U C U A C U U C G A m. RNA Ribosomes move over one codon

aa 1 peptide bonds aa 2 aa 4 aa 3 4 -t. RNA 2 -t. RNA A U G 3 -t. RNA G C U G A A C U U C G A A C U m. RNA

aa 1 peptide bonds aa 4 aa 2 aa 3 2 -t. RNA 4 -t. RNA G A U (leaves) 3 -t. RNA A U G G C U G A A C U U C G A A C U m. RNA Ribosomes move over one codon

aa 1 peptide bonds aa 5 aa 2 aa 3 aa 4 5 -t. RNA U G A 3 -t. RNA 4 -t. RNA G A A G C U A C U U C G A A C U m. RNA

peptide bonds aa 1 aa 5 aa 2 aa 3 aa 4 5 -t. RNA U G A 3 -t. RNA G A A 4 -t. RNA G C U A C U U C G A A C U m. RNA Ribosomes move over one codon

aa 4 aa 5 aa 199 Termination aa 200 aa 3 primary structure aa 2 of a protein http: //highered. mcgrawhill. com/sites/0072437316/s aa 1 tudent_view 0/chapter 15/ani mations. html# 200 -t. RNA A C U m. RNA terminator or stop codon C A U G U U U A G

Transcription & Translation • http: //highered. mcgrawhill. com/sites/0072437316/student_view 0/chapter 15/animations. html#