1. Protein Synthesis (Eukaryotes)
By Antara, Carla, Clariss and Theantay

2. DNA
DNA is located in the nucleus of a cell. It is a double helix shape and contains sequences of nucleotides. Each nucleotide has one of the 4 bases: Adenine (A) which always bonds with Thymine (T), and Cytosine (C) which always bonds with Guanine (G). Each stand of DNA is complementary to the other. The order of these nucleotides determines holds the genetic code for a protein.
Nucleotides

3. DNA Unwinds
The section of DNA that codes for the protein being synthesized is unwound and unzipped by the enzyme helicase.
Helicase

4. Two strands of DNA
One half of the DNA is the template strand. This is the strand that will be transcribed into mRNA. The other strand is the coding (anti-sense) strand. This has a complementary sequence of bases as in the template stand so contains the same sequence of nucleotides as will be in the mRNA that will be produced.
Template Strand
Coding Strand

5. RNA Synthesis
RNA Polymerase
RNA polymerase attaches to the template strand and creates a complementary length of mRNA. This is the primary mRNA. The coding stand of DNA is not used.
Coding Strand
Template Strand
mRNA

6. Differences between RNA and dna
Has the bases Adenine, Cytosine, Guanine and Thymine
Very long
The sugar-phosphate backbone is made of deoxyribose sugar
Double stranded
RNA:
Has the bases Adenine, Cytosine, Guanine and Uracil
Relatively short
The sugar-phosphate backbone is made of ribose sugar
Single stranded

7. RNA Processing
Primary mRNA
During RNA processing, which occurs in the nucleus, the introns in the primary mRNA are spliced out leaving only the exons in the mature mRNA.
Exon
Intron

8. Leaving the Nucleus
mRNA
The mature mRNA leaves the nucleus through a nuclear pore to go into the cytoplasm.
Nuclear Pore
Nucleus
Cytoplasm

9. Translation
Amino Acid
The ribosome attaches to the mRNA in the cytoplasm. It reads the codons (3 bases) in the mRNA that each code for a specific amino acid. The tRNA with the complementary anticodon to the codon will carry the specific amino acid.
tRNA loaded with Amino Acids
Ribosome
mRNA

10. Translation
The tRNA with the correct anticodon will be attracted to the binding site in the ribosome. The ribosome will add the amino acid it carries to the growing polypeptide chain and the tRNA will be released. The unloaded tRNA will be reattached to another of the same amino acid.
Binding Site
Loaded tRNA
Polypeptide Chain
Unloaded tRNA
Ribosome
mRNA

11. Primary proteins
Polypeptide chain - Primary protein
The completed chain of amino acids, called a polypeptide chain, is a primary protein.

12. Secondary proteins
The polypeptide chain arranges into two common shapes to form a secondary protein: the alpha helix (left) and the beta-pleated sheet (right). These are held in place by hydrogen bonds.

13. Tertiary Proteins
The alpha helix and beta pleated sheets fold into a complex 3 dimensional shape which is called a tertiary protein. For some proteins, this is the end of the road and the protein goes away to do what is was synthesized to do.

14. Quaternary proteins
Quaternary proteins are clusters of tertiary proteins which bind together to form one protein that does a specific job.