Protein Synthesis

Question 1

What is Translation>?

Answer 1

The Process by which an mRNA sequence is “read” to construct a string of amino acids that form a protein

Question 2

Do all genes make proteins?

Answer 2

no

Some just make RNA

Question 3

Which strand of mRNA is used as a basis for copying?

Answer 3

the antisense strand

Question 4

What is the difference between prokaryotes and eukaryotes in regard to transcription and translation?

Answer 4

In prokaryotes: transcription and translation are coupled

In eukaryotes: they are separated mRNA made in nucleus, then processed and goes to cytoplasm where translation occurs

Question 5

What do you need in order for Protein synthesis to occur - ingredients

Answer 5

Mature mRNA

ribosomes

Amino acids

accessory proteins

LOTS OF ENERGY!

Question 6

What are the 2 types of Ribosomes needed for Protein synthesis or translation?

Answer 6

Small subunit: 40S proteins 18S rRNA

Large subunit: 60S proteins 28S, 5.8S and 5S rRNA

Question 7

The Large ribosomal subunit utilized in protein synthesis/translation has 2 parts…what are they?

Answer 7

The P site (peptide site)

The A site (the acceptor site)

Question 8

What is the 3rd base pair in an anticodon called in protein synthesis?

Answer 8

the wobble base

Question 9

Which enzyme is utilized to attach amino acids to tRNAs during the process of translation?

Answer 9

aminoacyl-tRNA synthetase

Question 10

mRNA is read by the ribosome during translation in a series of ___nucleotides (codons)

Answer 10

3

Question 11

Where is the wobble base located?

Answer 11

In the anticodon loop

Question 12

What happens at the anticodon loop of tRNA?

Answer 12

that’s where mRNA will bind

Question 13

What is the prime energy source utilized in Protein Synthesis?

Answer 13

GTP

Question 14

What are the steps of Translation?

Answer 14

1) Methionine initiator RNA complex is brought to the small subunit (40S).
2) The two of them then recognize the start codon AUG on the mature mRNA and attach (initiation)
3) Then using energy to bind large ribosomal subunit to the complex at the start codon
4) GTP hydrolysis happens twice and Methionine tRNAi is in the P site
5) a tRNA carrying an amino acid is brought to the ribosome complex by an elongation factor - new tRNA is in the **A site **
6) Chain elongation occurs by adding amino acids to C-terminal end of polypeptide (reaction catalyzed by peptidyl transferase)
7) P site group is transferred to A site tRNA
8) Ribosome moves along chain by way of GTP energy release,
9) moves A site to the next codon in the 3’ direction
10) Termination: requires releasing factors eRF - binds to the A site of the ribosome with GTP and stop occurs at the A site
11) The ribosomal complex releases from the mRNA, the amino acid chain is released
12) made a protein but is took a lot of energy to get there!

Question 15

How do proteins made in the cytoplasm get inserted into a cell membrane?

Answer 15

Secretory Pathway

Question 16

How does the cell know where to send the finished protein once it is released during translation?

Answer 16

the first couple of amino acids code/signal for the specific destination of the protein

Question 17

How is protein expression regulated in the prokaryote?

Answer 17

by turning mRNA synthesis on and off

Question 18

What’s a polysome?

Answer 18

Several ribosomes can be translating on the same mRNA at the same time - synchronized movements - this is what forms a polysome

Question 19

From a pharmaceutical standpoint how do we regulate gene expression in prokaryotes with drugs?

Answer 19

Quinolones and fluoquinolones - interfere with DNA replication and transcription by targeting DNA gyrase or topoisomerase

Tetracyclines - interfere with translation - bind to 30S

Erythromycin - interfere with translation - bind to 50S

Chloramphenicol - interefere with translation by preventing peptide bond formation