3.4.2 | DNA AND PROTEIN SYNTHESIS

Question 1

define genome

Answer 1

the complete set of genes in a cell

Question 2

define proteome

Answer 2

the full range of proteins that a cell can produce

Question 3

describe the two stages of protein synthesis

Answer 3

transcription - production of mRNA from DNA in the nucleus
translation - production of polypeptides from the sequence of codons carried by mRNA at ribosomes

Question 4

describe the structure of tRNA

Question 5

describe the structure of mRNA

Question 6

describe how mRNA is formed by transcription in eukaryotic cells

Answer 6

hydrogen bonds between DNA bases break
only one DNA strands acts as a template
free RNA nucleotides align next to their complementary bases on the template strand
RNA polymerase joins adjacent RNA nucleotides, forming phopshodiester bonds via condensation reactions
pre-mRNA is formed and this is spliced forming mRNA

Question 7

describe how the production of mRNA in a eukaryotic cell is different from the production of mRNA in a eukaryotic cell

Answer 7

pre-mRNA produced in eukaryotes whereas mRNA is produced directly in prokaryotes because genes in prokaryotes do not contain introns so no splicing in eukaryotes

Question 8

describe how translation leads to the production of a polypeptide

Answer 8

mRNA attaches to a ribosome and the ribosome moves to a start codon
tRNA brings a specific amino acid
tRNA anticodon binds to complementary mRNA codon
ribosome moves along to next codon and another tRNA binds so two amino acids can be joined by a condensation reaction (using energy from hydrolysis of ATP)
tRNA released after amino acid joined polypeptide
ribosome moves along mRNA to form polypeptide, until a stop codon reached

Question 9

describe the role of ATP in translation

Answer 9

hydrolysis of ATP to ADP + Pi releases energy so amino acids join to tRNAs and peptide bonds form between amino acids

Question 10

describe the role of tRNA in translation

Answer 10

attaches to/transports a specific amino acid, in relation to its anticodon
tRNA anticodon complementary base pairs to mRNA codon. forming hydrogen bonds
2 tRNAs bring amino acids together so peptide bond can form

Question 11

describe the role of ribosomes in translation

Answer 11

mRNA binds to ribosomes with space for two codons
allows tRNA with anticodons to bind catalyses formation of peptide bond between amino acids moves along mRNA to next codon