Protein Synthesis Flashcards
Where are DNA molecules found in eukaryotic cells?
- Nucleus
- Mitochondria
Where are organelles making proteins found?
Cytoplasm
What is the purpose of mRNA?
Carries genetic code from the DNA in the nucleus [too big to leave nuclear pores] to cytoplasm for translation
Where is mRNA made?
In nucleus during transcription
Where is tRNA found?
Cytoplasm
Describe a tRNA molecule - 3
- Amino acid binding site at one end
- Sequence of 3 bases at the other end [anticodon] specific to amino acid its carrying
- Polypeptide folded by hydrogen bonds
What is the anticodon sequence?
Triplet of bases complimentary to the mRNA codon for a particular amino acid
What is the purpose of tRNA?
Carries amino acids used to make proteins to the ribosomes during translation
What is the purpose of a DNA template strand?
To act as a template to be transcribed to make an mRNA complimentary base strand
What is a ribosome formed from?
RNA and proteins
What is the purpose of transcription?
Converts DNA strand to mRNA complimentary strand
What is the purpose of translation?
Amino acids are joined up to form polypeptide chain following the sequence of codons in an mRNA strand
Explain how a mutation in the genetic code can cause a non functional protein
- Change to DNA triplet during replication
- Changes to mRNA codon
- So different anticodon needed: so different amino acid
- Changes primary structure of protein
- Different bonding e.g hydrogen/ionic bonds
- Changes tertiary structure
- Doesn’t carry out function
Explain how mutations can occur and there still be a functional protein produced
- DNA is degenerate
- Each amino acid is coded for by more than one triplet codon
- Change to DNA base e.g substitution may not cause change to amino acids in primary structure
- No change to bonding and therefore tertiary structure
Where does transcription take place?
The nucleus
Explain the process of transcription - 10
- RNA polymerase attaches to DNA at start codon
- DNA helicase seperates the DNA strands
- Breaks hydrogen bonds
- One of the strands becomes the template strand
- RA polyermase lines up free RNA nucleotides along side template strand
- RNA nucleotides pair up with specific bases on DNA strand by complementary base pairing and joined together by RNA polymerase
- Forms mRNA molecule
- Hydrogen bonds reform between DNA strands, winds back into double helix
- RNA polymerase reaches stop codon - detaches from DNA
- mRNA moves out of nucleus through nuclear pores
Where does translation take place?
Cytoplasm
Explain the process of translation - 11
- Ribosome binds onto mRNA at a start codon
- tRNA molecules carry amino acids to ribosome
- Codon is matched to anticodon by complementary base pairing
- Ribosome holds tRNA in place
- Amino acids joined together by peptide bond
- tRNA molecule moves away leaving amino acid behind
- Ribosome moves to next codon
- Used tRNA has the same amino acid reattached using ATP
- Process continues in producing chain of amino acid [polypetide]
- Ribosome reaches stop codon and moves away from polypeptide chain
- Protein is formed
