Lecture 16 Protein Synthesis

Question 1

Give an overview of Translation

Answer 1

The process by which ribosomes read the genetic message in mRNA and produce a protein product

Question 2

What is the role of transfer RNA

Answer 2

Plays a role as an adaptor that can bind an amino acid at one end and interact with the messenger RNA codon at the other end.

Question 3

Describe the process of amino acid charging

Answer 3

• Where the tRNA binds the amino acid to produce an amino acyl transfer RNA.
• Amino acid forms ester bond to t RNA
• A single molecule of ATP is consumed in the coupling of the amino acid to the transfer RNA.

Question 4

Which type of bond is formed during amino acid charging

Answer 4

Ester bond

Question 5

When a transfer RNA ester bonds to the amino acid, which molecule is consumed

Answer 5

single molecule of ATP is consumed.

Question 6

How is the start of the peptide chain detected in messenger RNA

Answer 6

The sequences upstream of the start codon AUG are recognized by the small ribosome subunit.

Question 7

Describe how translation is initiated

Answer 7

The 16 S RNA of the small ribosome subunit base pairs the Shine Dalgarno sequence in prokaryotes.

Question 8

What is the role of the Shine Dalgarno sequence

Answer 8

it is recognized by the small ribosome subunit which forms base pairs to the shine dalgarno sequence.

Question 9

Where is the Shine Dalgarno sequence located

Answer 9

Upstream of the AUG start codon. Sort of serves as a promoter region for translation.

Question 10

What happens if the Shine Dalgarno sequence is absent

Answer 10

The ribosome will ignore the first methionine AUG codon exposed if the Shine Dalgarno sequence is absent.

Question 11

Which part of the ribosome recognizes the Shine Dalgarno sequence in the mRNA.

Answer 11

The 16 S RNA of the smaller subunit.

Question 12

In which type of organism is the Shine Dalgarno sequence found in

Answer 12

Prokaryotes.

Question 13

What is the equivalent sequence to the Shine Dalgarno sequence for eukaryotes

Answer 13

The Kozac sequence

Question 14

How many tRNAs belong to the AUG start codon

Answer 14

2

one is used in intiation the other is used in elongation

Question 15

What happens to the start codon in prokaryotes.

Answer 15

Prokaryotic initiating methionine is formylated to form f MET.

Question 16

How many subunits does the ribosome have

Answer 16

2

Question 17

What is the name of the large ribosome subunit in prokaryotes

Answer 17

50S

Question 18

What is the name of the small ribosome subunit in prokaryotes 70s ribosomes

Answer 18

30S

Question 19

Describe the structure of prokaryotic ribosome

Answer 19

• Contains 70S ribosomes
• Large 50S subunit made up of 23 S RNA and 5 S RNA
• Small 30 S subunit made up of 16 S RNA

Question 20

Which types of ribosomal RNA comprise the i ) the small ribosome unit
ii ) the large subunit in 70 S ribosomes

Answer 20

small - 16 S RNA

Large - 23S and 5S RNA

Question 21

Which type of ribosomes are found in eukaryotes

Answer 21

80 S

Question 22

Describe the structure of the 80S ribosomes

Answer 22

• Large 60 S subunit

- Small 40 S subunit

Question 23

Describe the process of Translation initiation

Answer 23

Initiator transfer RNA and messenger RNA join the complex

Question 24

Which initiation factors and orther factors are involved in Translation Initiation

Answer 24

• IF2
• GTP
• ATP

Question 25

Initiation

Answer 25

- The 30S intiation complex is formed by the 30 S subunit plus messenger RNA and F met- trna. - The s

Question 26

How many stages are there in translation

Answer 26

3

Question 27

Which part of the transfer RNA do the amino acids bind to?

Answer 27

The 3' acceptor arm in a 2 step process.

Question 28

Describe the process of Amino acid charging a tRNA

Answer 28

- Amino acid binds to the tRNA 3' acceptor arm - 2 step process - Amino acid + ATP --> Amino Acid AMP + PP - AA AMP + tRNA --> AA tRNA + AMP

Question 29

Give the equations for Amino acid activation and state which energy carrier molecule is employed

Answer 29

Amino acid + ATP ---> Amino acid- AMP + PP Amino acid-AMP + tRNA --> Amino acid tRNA + AMP.

Question 30

How many transfer RNAs exist for Methionine start codon

Answer 30

2

Question 31

What distinguishes initiator methionine from elongation methionine

Answer 31

Initiating methionine is formylated, denoted as fMET

Question 32

Describe process of initiation in translation

Answer 32

30S Small ribsosome subunit is complexed with initiation Factor 1 and Initiation Factor 3 - IF2 is covalently coupled to a GTP molecule - IF2 binds the 30S subunit

Question 33

Describe the process of translation elongation

Answer 33

1) EF-Tu coupled with GTP binds a transfer RNA to the ribosomal A site. 2) A site - amino a

Question 34

Which molecules are involved in the formation of the ternary complex

Answer 34

Amino acyl transfer RNA, EF-Tu and GTP.