Protein Synethesis Flashcards
What is protein synthesis?
the production of proteins from the information contained within a cell’s DNA. Involves two main stages transcription and translation.
What is the structure of RNA
single polynucleotide strand that contains uracil (u) as a base instead of thymine which pairs with adenine during protein synthesis
What is the role/structure of messenger RNA? (mRNA)
Made during transcription. It carries the genetic code from the DNA to the ribosomes where it is used to make a protein during translation. It is a single polynucleotide strand. In mRNA groups of three adjacent bases are usually called codons (sometimes triplets)
What is the role/structure of transfer RNA (tRNA)
translation. It carries the amino acids that are used to make proteins to the ribosomes. tRNA is a single polynucleotide folded into a clover shape. Hydrogen bonds between specific base pairs hold the molecule in this shape. has a specific sequence of three bases at one end called an anticodon. Also has amino acid binding site at the other end. Anticodon is specific to amino acid it carries
What is an anticodon?
Triplet of bases on tRNA that is complementary to codon (triplet of bases on mRNA that codes for a specific amino acid) on mRNA
What is transcription?
Where the DNA code is copied into a molecule called mRNA. Eukaryotic (nucleus) prokaryotic (cytoplasm)
First stage of transcription (stages aren’t official)
- RNA polymerase attaches to the DNA at start of gene. Hydrogen bonds between the two DNA strands broken by DNA helicase attached to RNA polymerase separating strands so DNA molecule uncoils exposing some bases. One strand used as template to make an mRNA copy
Second stage of transcription
- Complementary mRNA is formed
RNA polymerase lines up free RNA nucleotides alongside exposed bases on template strand. Specific complementary base pairing means mRNA strand ends up being a complementary copy of the DNA template strand. Nucleotides joined together by RNA polymerase
Third stage of transcription
- RNA polymerase moves down the DNA strand
Assembling the mRNA strand
Hydrogen bonds reform and strands coil back into double helix
Fourth Stage Transcription
- RNA polymerase reaches stop signal ( particular sequence of DNA)
Stops making mRNA and detaches from DNA.
Eukaryotes- mRNA moves out of nucleus through nuclear pore and attaches to a ribosome in cytoplasm
Do prokaryotes use splicing and why/why not?
No, transcription results directly in production of mRNA from DNA. No introns
Why do eukaryotes use splicing, how does it occur?
Introns and exons are both copied into mRNA during transcription. Strands containing introns and exons are called pre- mRNA. Splicing- introns removed and the exons join together forming mRNA strands. Takes place in nucleus, then leaves nucleus for translation.
What is translation?
The production of polypeptides from the sequence of codons carried by mRNA. Occurs at ribosomes in the cytoplasm
Step 1 of Translation
mRNA attaches to a ribosome and tRNA molecules carry amino acids to it. ATP provides energy needed for bond between amino acid and tRNA molecule to form. (Ribosome binds to mRNA at start codon)
Step 2 of Translation
A tRNA molecule, that has an anticodon which is complementary to the mRNA’s start codon, attaches itself to the mRNA by complementary base pairing (codon matched to anticodon by complementary base pairing). Second tRNA molecule attaches itself to next codon on mRNA in same way. Ribosome holds tRNA in place.
