Topic 2 cells: Protein Synthesis

Question 1

2 steps of protein synthesis

Answer 1

transcription and translation

Question 2

what is the nucleur step of protein synthesis

Answer 2

transcription

Question 3

what is the cytoplasmic step of protein synthesis

Answer 3

translation

Question 4

Explain the steps of transcription

Answer 4

RNA polymerase transcribes DNA into RNA=>

1. messenger RNA (mRNA)
   Directs synthesis of polypeptide
2. Ribosomal RNA
   Part of ribosomes
   3.Transfer RNA (tRNA)
   Carries amino acids to ribosome for reaction

Question 5

Where does transcription take place

Answer 5

In the nucleus

Question 6

What 3 types of RNA does translation need and what is their functions?

Answer 6

Messanger RNA -from nucleus (mRNA)
Transfer RNA to carry amino acids (tRNA)
Ribosomes to do the actual work containing ribosomal RNA (rRNA)

Question 7

If released what can be post translationally modified?

Answer 7

Released polypeptide.

Question 8

Explain steps 1-6 of protein synthesis

Answer 8

1. Initiator tRNA attatches to a start codon
2. Large and small ribosomal sub units join to form a functional ribosome and initiator tRNA fits into position on the ribosome
3. Anti codon of incoming tRNA pairs with next mRNA codon beside initiator tRNA
4. Amino acid on initiator tRNA forms a peptide bond with amino acid beside it
5. tRNA leaves the ribosome: ribosome shifts by one codon, tRNA then binds to newly exposed codon

steps 3-5 repeat

6. Protein synthesis stops when the ribosome reaches the stop codon on mRNA