8.5- POLYPEPTIDE SYNTHESIS- TRANSLATION

Question 1

synthesising a polypeptide #1

Answer 1

ribosome becomes attached to starting codon (AUG) at one end of mRNA molecule

Question 2

synthesising a polypeptide #2

Answer 2

tRNA molecule with complementary anticodon sequence (UAC) moves to ribosome + pairs up with codon on mRNA
this tRNA carries specific amino acid (methionine)

Question 3

synthesising a polypeptide #3

Answer 3

tRNA molecules with complementary anticodon pairs with next codon on mRNA
this tRNA molecule carries another amino acid

Question 4

synthesising a polypeptide #4

Answer 4

ribosome moves along mRNA, bringing together two tRNA molecules at any one time, each pairing with corresponding two codons on mRNA

Question 5

synthesising a polypeptide #5

Answer 5

two amino acids on tRNA joined by peptide bond using enzyme + ATP which is hydrolysed to provide required energy

Question 6

synthesising a polypeptide #6

Answer 6

ribosome moves on to third codon in sequence on mRNA, thereby linking amino acids on second + third tRNA molecules

Question 7

synthesising a polypeptide #7

Answer 7

first tRNA released from its amino acid + is free to collect another amino acid from amino acid pool in cell

Question 8

synthesising a polypeptide #8

Answer 8

process continues with up to 15 amino acids being added each second, until polypeptide chain built up

Question 9

synthesising a polypeptide #9

Answer 9

up to 50 ribosomes can pass immediately behind first, so many identical polypeptides can be assembled simultaneously

Question 10

synthesising a polypeptide #10

Answer 10

synthesis of polypeptide continues until ribosome reaches stop codon
at this point, ribosome mRNA + last tRNA molecule all separate + polypeptide chain complete

Question 11

What does the DNA sequence of triplets that make up a gene determine?

Answer 11

sequence of codons on mRNA

Question 12

What does the sequence of codons on mRNA determine?

Answer 12

order in which tRNA molecules line up

Question 13

What does the order in which tRNA molecules line up determine?

Answer 13

sequence of amino acids in polypeptide

Question 14

What does a single polypeptide chain sometimes act as?

Answer 14

functional protein

Question 15

Often how many polypeptide chains give a functional protein?

Answer 15

often, number of polypeptides linked together to give functional protein (quaternary structure)

Question 16

What happens to the polypeptide chains when it makes a protein? (3)

Answer 16

polypeptide coiled/folded, producing its secondary structure

secondary structure folded, producing tertiary structure

different polypeptide chains, along with any non-protein groups, linked to form quaternary structure