Protein Synthesis

• Biology
• 10th Grade

Bell Ringer: Where are you on our learning scale with DNA replication?

1. 4 - I feel comfortable enough to teach others about it
2. 3 - I feel comfortable enough to draw it and tell what each part is
3. 2 - I know what it looks like but could not draw or describe it on my own
4. 1 - I am not comfortable with the structure of DNA

Today's Essential Question:

How is DNA used to make proteins?

Protein Review

• Proteins are macromolecules.
• Their monomers are amino acids.
• Amino acids form chains to create proteins.
• Proteins serve many important functions, including as enzymes, hormones, structure, and movement, in our bodies.

How are proteins made?

• There are two main steps to making a protein:

1) Step One: Transcription - where DNA copies one side of its bases to make RNA.

2) Step Two: Translation - where RNA is "decoded" to form a chain of amino acids, making a protein

What is RNA?

• RNA is a nucleic acid, made up of nucleotides.
• It also has four types of nucleotides, made unique by their bases.
• In RNA, there is adenine, cytosine, guanine, and uracil.

If RNA is missing thymine, what do you think adenine's base pair?

1. Cytosine
2. Guanine
3. Uracil
4. It doesn't have a base pair

Main Differences Between DNA & RNA

1. DNA is a double helix & RNA is a single helix
2. In DNA, adenine pairs with thymine (A-T), but in RNA, adenine pairs with uracil (A-U)
3. DNA always stays in the nucleus, but RNA can travel throughout the cell.

How is RNA made?

• RNA is made during Step 1: Transcription.  
• Just like in replication, DNA is "unzipped" by helicase.
• Then, RNA polymerase copies ONE side of the DNA molecule to create mRNA.
• Every set of 3 bases on the mRNA strand is known as a codon.

Transcription - notice how the A's pair with U's in the red mRNA strand.

Turn & Talk

How is DNA replication similar to transcription?

How is DNA replication different from transcription?

How are amino acids made from mRNA?

1) Amino acids are generated during Step 2: Translation

2) In this step, the mRNA travels out of the nucleus and attaches to a ribosome.  

3) Inside the ribosome, a tRNA brings the proper amino acid into the ribosome, along with the anti codon (the complementary group of three nucleotides that match the mRNA strand).

4) As each codon of the mRNA passes through the ribosome, a tRNA delivers its anticodon and the appropriate amino acid.

Translation - the tRNA deliver an anticodon that matches the mRNA strand codons to generate amino acids, which make a protein

Charts, like this one, can be used to figure out which amino acid is generated by which mRNA codon.