protein synthesis

Question 1

describe 3 differences between structure of tRNA and mRNA

Answer 1

1. tRNA is clover leaf shaped, mRNA is linear
2. tRNA has anitcodon, mRNA has codon
3. tRNA has amino acid binding site, mRNA does not

Question 2

describe and explain a difference in the structure of premRNA and mRNA (2)

Answer 2

1.mRNA has no introns
2. because of splicing

Question 3

describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation (3)

Answer 3

1. tRNA brings specific amino acid
2. anticodon on tRNA binds to codon on mRNA
3. amino acids join by condensation reaction using ATP

Question 4

describe how mRNA is produced from an exposed template strand of DNA (3)

Answer 4

1. RNA nucleotides form complementary base pairs
2. RNA polymerase joins RNA nucleotides
3. by forming phospodiester bonds between them

Question 5

describe how mRNA is formed by transcription in eukaryotes (5)

Answer 5

1. hydrogen bonds between bases break
2. one DNA strand acts as a template
3. RNA nucleotides align by complementary base pairing
4. uracil binds to adenine instead of thymine
5. RNA polymerase joins adjacent RNA nucleotides
6. by forming phosphodiester bonds between them
7. pre-mRNA is spliced to remove introns

Question 6

describe how a polypeptide is formed by translation of mRNA (6)

Answer 6

1. mRNA attaches to ribosome
2. tRNA anticodon is complementary to codon on mRNA
3. tRNA brings specific amino acid
4. amino acids join by formation of peptide bonds between them
5. in a condensation reaction using ATP
6. tRNA leaves ribosome once amino acid joins polypeptide
7. ribosome moves along mRNA to form polypeptide

Question 7

what is the proteome of a cell (1)

Answer 7

the full range of proteins a cell is able to produce

Question 8

the genetic code is degenerate, what does this mean (1)

Answer 8

several codons can code for the same amino acid

Question 9

define the term universal

Answer 9

in all organisms, the same triplets code for the same amino acids

Question 10

define the term non-overlapping

Answer 10

each codon codes for it’s own specific amino acid

Question 11

describe how mRNA is produced in a plant cell (5)

Answer 11

1. DNA strands separate by breaking H bonds
2. one strand is a template
3. complementary base pairing between A and U, T and A, C and G, G and C
4. RNA nucleotides joined by RNA polymerase
5. pre-mRNA is formed
6. splicing to remove introns

Question 12

give the 2 types of molecule from which a ribosome is made

Answer 12

• RNA
• protein

Question 13

describe the role of a ribosome in the production of a polypeptide (3)

Answer 13

1. mRNA binds to ribosome
2. ribosome has 2 binding sites
3. ribosome allows tRNA with anticodons to bind to codons
4. ribosome catalyses formation of peptide bond between amino acids
5. moves along mRNA strand

Question 14

describe how a gene is a code for the production of a polypeptide (3)

Answer 14

1. gene is a sequence of DNA bases
2. every three bases is a triplet
3. triplet codes for an amino acid, determines the order of amino acid sequence

Question 15

describe how monomers join to form the primary structure of a protein (3)

Answer 15

1. condensation reaction between amino acids
2. forms peptide bonds
3. determines order of amino acid sequence