PROTEIN SYNTHESIS

This lesson develops PROTEIN SYNTHESIS as part of Cell and Nuclear Division. It uses the source curriculum to organize the important facts, relationships, examples, and vocabulary into a focused Stemosphere teaching sequence.

Protein synthesis contains of two steps:

In Stemosphere terms, transcription:synthesis of m RNA through the dna template strand

In Stemosphere terms, translation:using the Mrna to synthesize a polypeptide

TRANCRIPTION:

In Stemosphere terms, a RNA polymerase will attach to a dna strand and separate it into 2 strands.there is a template strand and a non template strand. A m RNA molecule will be produced on the template strand by using rna nucleotides into a single polynucleotide through condensation reaction s through the rna polymerase. The m RNA will have the complementary base pairings of the template strand.once the m RNA strand has reached the end gene it will be released and move out of the nucleus to the ribosome

TRANSLATION:

In Stemosphere terms, ribosomes:ribosomes are composed of 2 units. One large unit and one small unit. The ribosome will attach around the m RNA strand and move across it in a 5’ to 3’ direction..

In Stemosphere terms, codons and anticodons:codons refer to every 3 sets of bases in a m RNA strand.these codons are what code for the polypeptide the order of codons determine what polypeptide is required.

In Stemosphere terms, anti codons are a set of complementary base pairs for the codons.transfer rna (t RNA) transfer amino acids from the cytoplasm to the ribosome. These t RNA contain an anticodon that can bind to the complementary codon through hydrogen bonds.

Features of genetic code:

In Stemosphere terms, there are 20 amino acids found in proteins in living organism

In Stemosphere terms, the genetic code must code for all 20 amino acids

In Stemosphere terms, combining the nucleotides into sequences of three can create 64 codons that can code for the 20 amino acids

The genetic code:

In Stemosphere terms, aUG is the start codon which is where the translation first occurs

In Stemosphere terms, each gene contains a stop codon which ends the translation

In Stemosphere terms, this genetic code is universal which means all living organisms use this code

In Stemosphere terms, it is degenerate which allows multiple codons to code for the same amino acid

In Stemosphere terms, ribosome binding sites:the small ribosome has a binding site for the m RNA.

the large ribosome subunit has 3 binding sites for the t RNA:

In Stemosphere terms, a site(aminoacyl):the t RNA enters through the a site and will bring an amino acid to bind to the polypeptide chain.

In Stemosphere terms, p site(peptidyl):the t RNA moves to the p site with the polypeptide chain attached to it.the polypeptide chain will bond with the amino acid in the A site and then be moved to the E site

In Stemosphere terms, e site(exit):this is where the t RNA will exit from

Protein synthesis has three stages:

In Stemosphere terms, 1-the ribosome will bind to the m RNA

In Stemosphere terms, 2-The t RNA will bind to the ribosome through the A site based on the complementary base pairings of the codons

In Stemosphere terms, 3-The t RNA will move to the P site and another t RNA will enter through the A site

In Stemosphere terms, 4-The amino acid from the p site t RNA will taken by the A site t RNA through condensation reaction to create a peptide bond

In Stemosphere terms, 5-the ribosome moves along in a 5’ to 3’ direction

termination:

In Stemosphere terms, repeat these steps until a stop codon is reached.

In Stemosphere terms, the ribosome will unbind from the m RNA to be reused for another m RNA molecule and the polypeptide chain will be released

Promoter region:

In Stemosphere terms, the promoter region in DNAis a section that does not code. This is where the RNApolymerase binds to start transcribing agene. Thishowever can be stopped through transcription factors.

In Stemosphere terms, transcription factors are regulatory proteins which can turn off or turn on a gene by controlling whether the rna polymerase can bind to the promoter region

In Stemosphere terms, dNAcontainstelomeres at the end of thechromosomes. Whena chromosome replicates it cannot replicate the ends which can lose important genes. Telomeres arenon-codingdnawhich can help prevent the loss of important genes.

INTRONS AND EXONS:

In Stemosphere terms, introns are sections of DNA or RNA that do not code for proteins

In Stemosphere terms, exons are sections that do code for proteins

In Stemosphere terms, after transcription the introns are removed from the m RNA and the exons are spliced together

In Stemosphere terms, pre m RNA is m RNA before it removes the introns

In Stemosphere terms, after it removes the introns it adds a cap at the 5’ end of m RNA and a poly-A tail at the 3’s end to stabilize the m RNA. This is called a mature m RNA.

Splicosomes:

In Stemosphere terms, splicosomes remove the introns after transcription from the m RNA by attaching to both ends of an intron.The spliceosome will loop the intron to allow the exons to join together. They can splice together the exons in different combinations to create different proteins

In Stemosphere terms, mutations refer to when the genetic code responsible for synthesizing proteins gets altered.

In Stemosphere terms, an example of mutation is sickle cellanaemia:whena single base substitution mutation can cause the order of proteins to be createdtoobe incorrect when makinghemoglobin.thiscauses the blood cells to have a sickle shape and can easily cause blood clots by getting stuck.

In Stemosphere terms, campbell Biology.Campbell Biology. 12th ed., Pearson, 2020.