Module 2.3 proteins Flashcards
What are proteins?
A large polymer made of long chains of amino acids held together by peptide bonds .
What is the structure of an amino acid?:
centralised carbon atom with an amino group (-NH2 , a carboxyl (-OOH) group and an R group. Amino acids contain the elements hydrogen, carbon and oxygen, with some containing sulfur.
How is a peptide bond formed and what do they hold together?:
What about if theres 2 or more amino acids?:
Amino acids are held together by covalent bonds called peptide bonds. They are formed from condensation reactions in which H2O is released, and these bonds can break from hydrolysis.
2 Amino acids joined together are called a dipeptide bond, and a longer chain is held by polypeptide bonds.
What are the 2 stages of protein synthesis?
Transcription: The process of making mRNA from a DNA template
Translation: The process of translating the sequence of mRNA to a sequence of amino acids. (Forming Polypeptides)
What are the 3 stages of transcription?: (summary)
1) the gene to be transcribed unwinds and unzips, hydrogen bonds between bases are broken.
2) Free RNA nucleotides hydrogen bond with the exposed bases on the template strand (U replaces T)
3) RNA polymerase forms phosphodiester bonds between the ribose - phosphate groups.
The coding strand carries of the genetic code; the template strand is the complement. The mRNA formed is a copy of the coding strand.
What are the 5 stages of translation?:
1) The mRNA leaves the nucleus and attaches to a ribosome.
2) The ribosome reads the mRNA one codon at time.
3) Hydrogen bonds form between the tRNA anticodon and mRNA codon.
4) The amino acid from the tRNA is passed to the ribosome and the ribosome moves to the next codon.
5) As another amino acid is added a peptide bond forms between amino acids and a polypeptide is formed.
What is tRNA?:
Transfer RNA (tRNA) Transfer amino acids to the ribosome, shaped from a single strand looped into a clover leaf shape. One end of the tRNA has a triplet base anti-codon which complements the codon of the mRNA. A specific amino acid binds to the top of the molecule. Hydrogen bonds hold the molecule in shape.
What is mRNA?:
Messanger RNA is a small strand of nucleotides which is complementary to the coding strand of a gene from DNA. It will leave the nucleus through a nuclear pore and travel through the cytoplasm until it attaches to a ribosome.
