Protein Synthesis

Question 0

What are the two main stages in protein synthesis?

Answer 0

Transcription and translation

Question 1

What is transcription and where does it occur?

Answer 1

Transcription is the process of producing a strand of mRNA from DNA

It occurs in the nucleus of a cell

Question 2

What is translation and where does it occur?

Answer 2

Translation is the process of producing protein from a strand of mRNA

It occurs at the ribosomes

Question 3

What are the three stages of transcription?(IET)

Answer 3

Initiation, elongation, termination

Question 4

What happens during initiation?

Answer 4

RNA polymerase binds to a molecule of DNA and begins to unwind it.

The exposed DNA can now be transcribed

Question 5

What happens during elongation?

Answer 5

A complementary strand of mRNA is produced from the DNA template.

Question 6

What direction is mRNA produced?

Answer 6

5’ to 3’ direction

Question 7

What happens during termination?

Answer 7

RNA polymerase recognizes the terminator sequence at the end of the gene the strand of mRNA is released

Question 8

What happens to the strand of mRNA before it enters the cytoplasm for translation?

Answer 8

It adds a 5’ cap (7 G’s)

Adds a poly A tail

Removes introns

Question 9

What does the addition of a 5’ cap do for the strand of mRNA?

Answer 9

Protects the mRNA from being digested in the cytoplasm

Helps bind to ribosomes in cytoplasm

Question 10

What does a poly a tail do?

Answer 10

It attaches to the 3’ end of of mRNA

It prevents the mRNA from being digested in the cytoplasm

Question 12

What are introns and what do they do?

Answer 12

Introns are nonsense coding found on mRNA that if translated would interfere with the functioning of the protein

They are removed before mRNA leaves the nucleus.

Question 13

What is a triplet code and what is it referred to as?

Answer 13

A triplet code is when a strand of mRNA is translated into a polypeptide, every three bases will correspond to an amino acid

The three bases are referred to as a codon

Question 14

What are the three major molecules involved in translation?

Answer 14

mRNA, tRNA and ribosomes

Question 15

What are ribosomes? Describe their structure

Answer 15

Organelles that bind to and read the mRNA strand. Consists of 2 subunits: a large subunit and a small subunit.

Have three sites used in translation: A site (acceptor site), P site (peptide), E site (exit site)

Question 16

What is tRNA?

Answer 16

tRNA is a single stranded RNA molecule that is folded onto itself

It has 2 major subunits: anticodon ( binds to mRNA) and a terminal arm which carries the corresponding amino acid.

Question 17

What are the three stages of translation?

Answer 17

Initiation elongation and termination

Question 18

What happens during initiation?

Answer 18

The small ribosomal subunits bind to the 5’ cap on the mRNA

The small subunits move down the strand in a 5’ to 3’ direction

Once the start codon reaches the P site (peptide site), the large ribosomal subunit binds an translation begins

Question 19

What happens during Elongation of translation?

Answer 19

The tRNA molecule enters the A (active site)

A peptide bond forms

The ribosomes move down the strand of mRNA and the molecules of tRNA move into the P and E sites

Once the TRNA molecule reaches the E site an new molecule enters the A site and the process repeats

Question 20

What happens during termination In translation?

Answer 20

The ribosome reaches the stop codon and an enzyme stops the translation process.