Protein Synthesis Notes

(409-410)

Steps of DNA Transcription Making mRNA from DNA

1. Helicase does NOT unzip DNA at the gene of interest

2. RNA polymerase unwinds and matches RNA nucleotide bases to DNA, using one side as a template.

3. The mRNA strand is created. It now compliments the original DNA strand (G-C and A-U).

4. Ligase helps the strand of DNA to close and again.5. mRNA strand moves out of nucleus to ribosomes,

and the DNA zips up.

Key Players in TranslationrRNA = RNA that makes up a ribosome

tRNA = RNA that transfers specific amino acids

mRNA = carries the DNA message;

RNA transcribed from DNA

Codon = 3 nucleotides in a row on a strand of mRNA that code for an amino acid

Anticodon = 3 nucleotides in tRNA that base pair with the codon

Amino Acids = monomers of proteins (20 in humans)

Steps to TranslationMaking proteins from mRNA

1. Ribosomes attach to the “start” codon of mRNA (AUG), signaling the beginning of the protein chain

2. mRNA codons are matched to corresponding tRNA anticodons and appropriate amino acids are strung together.

3. Dehydration synthesis occurs between the amino acids, and they join, making a protein chain with peptide bonds in between

4. Ribosomes detach when they come across a “stop” codon (UAA, UAG, UGA). Protein synthesis is complete.

Why do you think RNA

uses the “triplet code”?

Do the math on your own or

with a neighbor.

CODON BINGO

• Fill in the Bingo Card (on page 45) with the 20 different amino acids.– Use your table on page 44 to help– Watch out for repeated amino acids!

• Wait for your teacher to begin calling out DNA letters to begin playing

Translation Activity

• You and your classmates need to discover the hidden protein in your bag.

• Follow the instructions in the bag to unlock the mystery protein.

What if a single base is changed?

What if a single base is changed?

What if a single base is changed?

Proteins

• Made up of Carbon, Hydrogen, Oxygen and Nitrogen (and some Sulfur)

• Proteins are responsible for many reactions

Types of Proteins

1. Enzymes = Catalysts that speed up the rate of a chemical reaction – Build up or break down substrate

• Fit together with its substrate like a “lock” and a “key”

– Not used up in the reaction– Work in a very specific biological range– Usually end with “-ase”

Hi sweeties, Do you remember

me?

In addition to what you know. I am a

substrate.

I am an enzyme. I am going to try to convert you.

I am now a product.

I am a glucose now.

I am a product, too. I am a fructose now.

I am completely unchanged, and

ready for some more sucrose!

I am the active site. The substrate binds

to me.

Proteins

2. Structural Proteins– Provides mechanical support to cells and

tissues

3. Transport Proteins– Transports small ions or molecules

4. Motor Proteins– Enables structures to move

Proteins

5. Hormones (signaling proteins)– Carries signals from cell-to-cell– e.g., insulin

6. Storage– Stores small molecules or ions– e.g., iron is stored in the liver in ferritin

7. Other specialized functions– Defense (immune system antibodies), – Receptor proteins (in eyes and muscles to

detect stimulus)