Chapter 4.13 Protein Synthesis

Question 1

What is a ribosome?

Answer 1

It is the site of protein synthesis

• Thousands of ribosomes per cell
• Combination of rRNA and protein
• E. coli has 52 distinct ribosomal proteins

Question 2

What are the two subunits of a ribosome?

Answer 2

30S and 50S in prokarayotes

• S = Svedberg units

Question 3

What are the three main steps of translation?

Answer 3

1. ) Initiation
2. ) Elongation
3. ) Termination

Question 4

Which step of translation does this describe?

Two ribosomal subunits assemble with mRNA.

Begins at the AUG start codon.

Answer 4

Inititation

Question 5

What does the process of Elongation entail?

Answer 5

Amino Acids are brought to the ribosome and are added to the growing polypeptide.

Question 6

What ribosome sites does elongation occur?

Answer 6

The A and P sites

Question 7

What is the movement of the tRNA holding the polypeptide from the A to the P site?

Answer 7

Translocation

Question 8

What is the third step of translation, and what occurs?

Answer 8

Termination, occurs when ribosome reaches a stop codon

• Ribosome subunits then dissociate

• Subunits free to form new initiation complex and repeat
process

Question 9

What is a Release Factor (RF)?

Answer 9

Recognizes the stop codon and cleave polypeptide from tRNA

Question 10

What is a complex formed by ribosomes simultaneously translating mRNA?

Answer 10

Polysomes