protein synthesis
DESCRIPTION
PROTEIN SYNTHESIS. In this experiment we modeled the structure of DNA and the processes involved in protein synthesis. DNA Structure. DNA is a double stranded helix molecule made of subunits called nucleotides. Each nucleotide contains a sugar ( deoxyribose ), a phosphate, and a base. - PowerPoint PPT PresentationTRANSCRIPT
PROTEIN SYNTHESISIn this experiment we modeled the structure of DNA and the processes involved in protein
synthesis
DNA StructureDNA is a double stranded helix molecule made of
subunits called nucleotides.
Each nucleotide contains a sugar (deoxyribose), a phosphate, and a base.
There are four bases (adenosine, thymine,
cytosine and guanine). Alternate sugar and phosphates form the
sides with bases connected to the sugars
making “rungs” like a ladder.
The chemical structure of the bases allow them
each to pair up with only one other base, thus they
form complementary pairs.
Protein SynthesisInformation about the number, type and sequence
of amino acids necessary to make a protein molecule, is found as a code in the DNA. This code is
in the sequence of bases. One gene sequence codes for one polypeptide. A set of 3 bases (a
codon) codes for one amino acid of a polypeptide. A protein is made of one or a small number of
polypeptides.
Equipment• 42 tooth picks representing the bonds
between the chemicals• 18 milk bottle lollies cut in half (36
halves) representing sugar• 18 raspberry lollies (36 halves)
representing phosphate units• 25 jelly beans halved (5 each of 5
colours) representing bases• 4 different jelly snakes 6cm long
representing amino acids
• A4 white paper representing a cell• Coloured paper circle, 6cm diameter,
representing a ribosome• Clean sharp knife • Cutting board• Gloves• Scissors• Marking pen• Heinemann Biology textbook
Transcription
A gene length of DNA unwinds in the nucleus.
RNA polymerase enzyme moves along the exposed single DNA strand linking
complementary RNA nucleotides together to form a messenger RNA strand. RNA contains
the base uracil where thymine is found in DNA.
The start codon (AUG) and a stop codon control the length of the mRNA strand.
The mRNA strand is then modified to remove non-coding regions called introns. Protein
coding regions, exons, are spliced together.
The modified mRNA moves out of the nucleus into the cytoplasm.
In the cytoplasm, an enzyme attaches amino acids to tRNA molecules. Each type of amino
acid is attached to its specific tRNA.
TranslationThe start codon (AUG) end of the mRNA strand binds onto a ribosome. A tRNA carrying the amino acid methionine and anticodon (UAC) binds to the mRNA start codon within the
ribosome.A second tRNA binds to the next codon. Its amino acid links
with a polypeptide bond to the first amino acid.
The first tRNA is released from the ribosome. The ribosome moves along the mRNA strand one codon
at a time. Two tRNAs at a time are temporarily bound within the ribosome and their amino acids linked
together. A polypeptide chain forms.
When a stop codon is reached the polypeptide chain is released into the cytoplasm. The chain folds on itself and may join other polypeptides to form a protein. Its
specific shape is vital for its particular function.