PROTEIN SYNTHESIS

Question 1

The format

Answer 1

dna - rna - protein

Question 2

stages of protein synthesis

Answer 2

Transcription and translation

Question 3

Transcription

Answer 3

transcription is a process where a relevant gene in dna is copied into a molecule of rna called the messenger rna or mRNA.

Question 4

Process of transcription

Answer 4

1. the dna helix unzips and unwinds as the hydrogen bonds between complementary base pairs break.
2. two separate polynucleotide strands are formed. one strand called the anti sense strands acts as a template .
3. free rna nucleotides now bind to the complementary base pairing to make a single strand of mRNA.
4. RNA polymerase forms sugar phosphate bonds between nucleotides.
5. the mrna detatches from the anti sense strand and leaves the nucleus through a pore in the nuclear envelope to the cytoplasm.
6. the two strands are joined together by complementary base pairing.
7. the dna molecule returns to its helix shape.

Question 5

Features of the genetic code

Answer 5

1. non overlapping
2. degenerateing
3. universal
4. triplet code

Question 6

mrna is much shorter than dna why

Answer 6

so that its able to carry the genetic code to ribosome in cytoplasm to enable the proteins to be made.

Question 7

pre mRNA

Answer 7

the pre mrna needs to be modified before it goes to the cytoplasm.

pre mrna is the primary transcript which consists of both coding and non coding regions.

Question 8

splicing / removal of introns

Answer 8

introns have to be removed from the mrna before it goes to the cytoplasm. introns are spliced out by a protein called splicosome. they just leave behind the coding regions called the extrons.

Question 9

translation

Answer 9

the process by which the sequence of bases in mRNA is concerted into sequence of amino acids in a polypeptide.

Question 10

stages of translation

Answer 10

1. once the modified mRNA leaves the nucleus through nuclear pore and enters the cytoplasm, it is attatched to the ribosome. the ribosome is attatched to the start codon.
2. a tRNA molecule with complementary anti codon binds to the start codon and is held in place by ribosome.
3. the ribosome moves along with mrna by one codon.
4. the enzymes delivered by the tRNA are joined together by a peptide bond. it is catalysed by an enzyme and requires ATP.
5. This process continues until the mrna reaches the stop codon.
6. The polypeptide chain is now created and it will enter the golgi bodies for modification.

Question 11

4 types of rna

Answer 11

1. mRNA - used in transcription
2. tRNA - used in translation
3. rRNA - found in ribosomes
4. siRNA - to prevent translation in mRNA.

Question 12

After translation

Answer 12

1. once the polypeptide chain is produced from the RER, it is then transferred to golgi apparatus.
2. the golgi apparatus is a sysyem of specialised membranes responsible for packaging, processing and modification.
3. some proteins have carbohydrate added to form a glycoprotein.
4. the golgi apparatus packages the protein in a secretory vesicle which fuses with the cell membrane to release protein from the cell.

Question 13

introns

Answer 13

introns are the sequence of bases in dna that do not code for
amino acids. also called as junk dna.

Question 14

proteome

Answer 14

the proteome is a number of different proteins that a cell is able to produce.