Protein Synthesis

1
Protein Synthesis

• Part 2 Translation

2
Translation

• Assembling a protein using the instructions
  carried by mRNA
• Where? Ribosomes!

Nucleus
Messenger RNA is transcribed in the nucleus.
mRNA
3
Proteins

• Proteins are chains of amino acids (AA)
• Proteins are also called polypeptide chains
• There are 20 amino acids. Examples
• Methionine (Met)
• Serine (Ser)
• Valine (Val)
• Alanine (Ala)
• Different proteins have different AA sequences
  Met Val Ala Cys Val - Ser

4
The Genetic Code

• Codon three consecutive nucleotides on mRNA
• Each codon specifies an AA
• AUG -gt Methionine (Met)
• UCA -gt Serine (Ser)
• The sequence of codons on mRNA determine the
  sequence of AAs in the protein

5
The Genetic Code

• mRNA
• UCGCACGGU
• UCG-CAC-GGU
• Ser His - Gly

6
Types of RNA

• mRNA messenger RNA
• Carries instructions from nucleus to ribosome for
  protein synthesis
• rRNA ribosomal RNA
• What ribosomes are made of (made in the
  nucleolus)
• tRNA transfer RNA
• Carry AAs to ribosome as proteins are assembled

7
tRNA

• Carries an AA on one end
• Has an anticodon on the other end
• Anticodon is complementary to the codon on mRNA
• What is the anticodon for UCG?
• What is the anticodon for CAC?
• What is the anticodon for GGU?

8
Translation
9
Animation
The Polypeptide Assembly Line The ribosome
joins the two amino acidsmethionine and
phenylalanineand breaks the bond between
methionine and its tRNA. The tRNA floats away,
allowing the ribosome to bind to another tRNA.
The ribosome moves along the mRNA, binding new
tRNA molecules and amino acids.
Growing polypeptide chain
Ribosome
tRNA
Lysine
tRNA
mRNA
Completing the Polypeptide The process continues
until the ribosome reaches one of the three stop
codons. The result is a growing polypeptide
chain.
mRNA
Ribosome
Translation direction
10
A Real Life Example!

• Firefly Animation

11
Review

• The process of making a protein from the codes on
  mRNA is called_________.
• How many RNA base pairs (nucleotides) make an
  amino acid?
• What are three base pairs (nucleotides) on the
  mRNA strand called?
• What are the three base pairs (nucleotides) on
  the tRNA called?
• tRNA carries __________ to the ______
• Proteins are made up of a chain of ______

translation
three
codon
anticodon
amino acids (aa) ribosome
aa