protein synthesis

Question 1

gene

Answer 1

sequence of nucleotide bases in a DNA molecule that codes for an amino acid

Question 2

protein synthesis stages

Answer 2

transcription
translation

Question 3

transcription definition

Answer 3

DNA is transcribed and a mRNA molecule is produced

Question 4

translation definition

Answer 4

mRNA is translated and an amino acid sequence is produced

Question 5

where does transcription happen

Answer 5

nucleus

Question 6

step 1 transcription

Answer 6

part of the DNA molecule unwinds due to DNA helicase and the hydrogen bonds between complementary base pairs break
- exposes gene to be transcribed)

Question 7

step 2

Answer 7

free activated RNA nucleotides line up alongside the antisense strand and pair up

Question 8

step 3

Answer 8

RNA polymerase moves along the antisense strand in the 3’ to 5’’ direction, and catalyse the formation of phosphodiester bonds between the nucleotides via. condensation reaction
- this forms an mRNA stand

Question 9

step 4

Answer 9

RNA polymerase continues until the STOP codon where transcription stops.

Question 10

step 5

Answer 10

mRNA detaches from the antisense strand and leaves through the nuclear pores and enters the cytoplasm where it travels to the ribosomes on the RER

Question 11

where does translation take place

Answer 11

ribosomes in the cytoplasm

Question 12

how does the ribosome attach to the mRNA

Answer 12

the small sub-unit attaches, and reads one triplet codon on the mRNA at a time

• large subunit joins the amino acids to form the polypeptide chain

Question 13

step 1 translation

Answer 13

• mRNA attaches to the ribosome at an AUG start codon

Question 14

step 2

Answer 14

tRNA carries a methionine and attaches itself to the start codon by pariring its anti-codon bases with the complementary codon bases

Question 15

step 3

Answer 15

another tRNA with its attaches amino acid (glycine) binds to the next codon along the chain

Question 16

step 4

Answer 16

the ribosome moves along the mRNA and a peptide bond is made between 2 amino acids, then the tRNA molecule leaves the ribosome and picks up another methionine until it reaches the stop codon

Question 17

tRNA function

Answer 17

bind to a specific amino acid and transport it to the ribosome

Question 18

explain tRNA activation

Answer 18

• amino acids are activated by combining with the tRNA.
• each tRNA has an anticodon which is complementary to the triplet codon on the mRNA
• the anticodon binds with the codon
• each tRNA binds to its specific amino acids, this process uses ATP and is catalyzed by enzymes