Polypeptide Synthesis - Translation Flashcards
What is the function of messenger RNA (mRNA) in protein synthesis?
mRNA carries the genetic code (sequence of codons) from DNA to the ribosomes, where it is translated into a sequence of amino acids
What is a codon?
A codon is a sequence of three nucleotide bases on mRNA that codes for a specific amino acid
What is the role of transfer RNA (tRNA) in translation?
tRNA carries specific amino acids to the ribosome and matches its anticodon with the codon on the mRNA
What determines which amino acid tRNA molecule carries?
The specific anticodon on the tRNA determines the amino acid it carries
Describe the process (simplified) of translation in protein synthesis?
Ribosomes mve along the mRNA, tRNA molecules bind to codons through complementary anticodons, bringing specific amino acids which joined together to form a polypeptide
What is an anticodon?
An anticodon is a sequence of three bases on the tRNA molecule that is complementary to a codon on the mRNA
What happens when mRNA leaves the nucleus?
When mRNA leaves the nucleus, it passes through the nuclear pore and attaches to a ribosome to begin the synthesis of a polypeptide
What links the amino acids together during translation?
A peptide bond formed using an enzyme and energy from ATP hydrolysis
How many tRNA molecules can pair with mRNA codons at a time on a ribosome?
Two tRNA molecules can be positioned at once on the ribosome, each pairing with a codon
What happens to the first tRNA after it releases its amino acids?
It detaches and returns to the cytoplasm to collect another specific amino acid
When does translation of a polypeptide end?
How can multiple identical polypeptides be produced simultaneously?
When the ribosome reaches a stop codon on the mRNA
Up to 50 ribosomes can follow the firt one along the same mRNA strand
Outline the full process of translation in protein synthesis: (9 steps)
{1} A ribosome attaches to starting codon at one end of the mRNA molecule
{2} A tRNA molecule with complementary anticodon sequence moves to ribosome and pairs up with codon on mRNA
{3} A tRNA molecule with a complementary anticodon pairs with the next codon on the mRNA. This tRNA molecule carries another amino acid
{4} The ribosome moves along the mRNA, bringing together two tRNA molecules at any one time, each pairing up with the corresponding two codons on the mRNA
{5} The two amino acids on the tRNA are joined by a peptide bond using an enzyme and ATP which is hydrolysed to provide the required energy
{6} The ribosome moves on to the third codon in the sequence on the mRNA, thereby linking the amino acids on the second and third tRNA molecules
{7} As this happens, the first tRNA is released from its amino acid and is free to collect another amino acid from the amino acid pool in the cell
{8} The process continues in this way, with up to 15 amino acids . being added each second, until a polypeptide chain is built up
{9} The synthesis of a polypeptide continues until a ribosome reaches a stop codon. At this point, the ribosome, mRNA and the last tRNA molecule all separate and the polypeptide chain is complete
What determines the sequence of codons on mRNA?
What does the sequence of codons on mRNA determine?
The sequence of DNA triplets in a gene
The order in which tRNA molecules line up during translation
Why do genes effectively control the activities of cells?
This is because many of the proteins they code for are enzymes, which regulate cellular reactions
What is a functional protein sometimes made from?
A single polypeptide chain or multiple polypeptides linked together (quaternary structure)
How is the tertiary structure of a protein formed?
By further folding of the secondary structure
What is formed when a polypeptide chain is coiled or folded?
The secondary structure of the protein
What forms the quaternary structure of a protein?
The linking of multiple polypeptide chains and any non - protein groups
What determines what happens to a polypeptide after translation?
The type of protein being made
