6.3a Translation (CQ - exam)

Question 1

4 major components of the translation machinery/initiation complex

Answer 1

1. tRNA
   - Delivers amino acid (AUG - Met) to the ribosome
2. Small ribosomal subunit
   - Binds to the 5’ cap on the mRNA
   - binds to the tRNA from methionine
   - Going to read until UAC (anticodon, stop sequence)
3. mRNA
   - Refers the information for protein synthesis to the ribosome
4. Large ribosomal subunit
   - Binds to indicate for the ribosome to become active
   - Has the ribosomal binding site
   - Brings in tRNA with the amino acid
   - Created peptide bonds between amino acid
   Exits the empty tRNA

Question 2

define codon, & anticodon

Answer 2

Codon is a sequence of 3 consecutive nucleotides that are part of the genetic code, it can specify for a particular amino acid, stop sequence, or start sequence.

Anticodon is a sequence of 3 nucleotides that are complementary to a specific mRNA codon

Question 3

function of tRNA.

Answer 3

used in the moving of amino acid to the ribosome. tRNA is single stranded and can be used as a template for replication.

Question 4

three ribosomal binding sites for tRNAs

Answer 4

1. Acceptor site
   A-site is a site in the ribosome; tRNA brings in an amino acid here
2. Peptide site
   P-site is a site in the ribosome; peptide bonds formed between amino acids
3. Exit site
   E-site is a site in the ribosome; empty tRNAs are sent here before exiting

Question 5

why translation is an energy-consuming process.

Answer 5

purpose of translation is to grow an amino acid chain, and each amino acid being added consumes 4 ATP

Question 6

what occurs in each of the 3 stages of translation.

Answer 6

1. Initiation
   - This phase is when all the subunits
   aminoacyl-tRNA binds with the small subunit of the ribosome; 5’ cap binds to the small subunit; large subunit binds
2. Elongation
   - This phase is when protein synthesis occurs
   - Polypeptides grow longer; tRNA codons bind to mRNA codons;
3. Termination
   - A stop codon is reached which is the release factor for the polypeptide chain
   - The ribosomal subunits separate; mRNA can enter another ribosome; then polypeptide after being released is folded and carry out functions.

Question 7

Streptomycin is an antibiotic that works by inhibiting the attachment of tRNA that carries methionine. Explain what effect this antibiotic must have on bacteria.

Answer 7

• Methionine is the start codon, aka first amino acid
• Needed for the initiation complex
• If it is unable to attach then no translation will occur