BIO 12 UNIT 2: Study Notes

PROTEIN SYNTHESIS

• Transcription:

• Occurs in nucleus of eukaryotic cells
• Definition:
Making a mRNA from a DNA template
• STEP 1-
DNA Helicase unzips and unwinds a double-helix DNA molecule
• STEP 2-
RNA Polymerase aids in matching RNA nucleotides to the DNA template strand (only one of the two DNA strands) [COMPLIMENTARY BASE PAIRING]
• STEP 3-
Completed mRNA strand leaves the nucleus and goes to the ribosome (also, DNA is rewound)

• Translation:

• Occurs at the ribosome of eukaryotic cells

• Definition: Production of a protein

• STEP 1- mRNA attaches to the ribosome (this is the strand from the aforementioned process of Transcription) [INITIATION]

• STEP 2- tRNA: an amino acid head and anti-codon tail that complimentary pairs to a specific codon of the mRNA strand (3 a.a. group) that results in the release of its specific amino acid head (coded for via base pairing between anti-codon and mRNA codon); only two tRNA molecules are at the ribosome releasing their amino acids at one time 

• STEP 3- Peptide bonds form between each pair of amino acids 

• STEP 4- mRNA shifting along the ribosome similar to a conveyor belt in that two tRNA arrive, release the amino acid and than move away to allow a new tRNA to come and release its amino acid head and so on this process occurs at an extremely quick pace [ELONGATION]

• STEP 5- Emptied tRNA molecules (i.e. no amino acid head) leave the ribosome after releasing an amino acid (their job is done)

• STEP 6- The completed long strand of amino acid monomers joined together to form a protein designated for a very specific role in the cell relating to a chemical reaction (enzymes); [TERMINATION] occurs which basically breaks apart the ribosome and allows the protein to exit and go where it needs to go to complete its function in the cell 




Here is a video explaining Protein Synthesis...

http://www.youtube.com/watch?v=D3fOXt4MrOM



but really who needs that when I made my very own SHOW ME video (link on blog) ;)