Making Proteins
This image summarizes the processes of transcription and translation.
mRNA rRNA
What are the three stages in this process
(central dogma) and where are they in this picture?
DNA protein tRNA

RNA
• RNA (Ribonucleic Acid)
– Contains Ribose as the sugar in its sugarphosphate backbone
• RNA has Uracil rather than Thymine as a base
– Base pairs: A – U C – G
• 3 types of RNA
– messenger (mRNA)
– transfer (tRNA)
– ribosomal (rRNA)

1. Transcription: mRNA is made from a strand of DNA
2. Translation: Protein is made by a ribosome by using mRNA as the set of
“instructions.”

• DNA is transcribed into mRNA

• mRNA serves as the instructional material to make proteins

• DNA is transcribed into pre-mRNA

• Non-coding regions of the mRNA, called introns , are removed from the pre-mRNA.

• The mRNA with only the coding region (the exons ) leaves the nucleus.
• Translation from mRNA to protein occurs in the cytoplasm.

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.

rRNA = 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)

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.

• 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?

• Made up of Carbon , Hydrogen , Oxygen and Nitrogen (and some Sulfur )
• Proteins are responsible for many reactions

I am completely
1. Enzymes = Catalysts that speed up the rate of a chemical reaction to convert you.
to me.
I am now a product . product , too.
I am a fructose now.
I am a glucose now.
– Usually end with “-ase”

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

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)

• Proteins monomers are called amino acids
– Peptide Bond:
Bond between 2 Amino Acids:
H
2
O

• A chain of amino acids are called
“polypeptides”
Poly peptides “ Many Peptides ”
• Polypeptides fold and twist to form a specific shape
• Two or more polypeptides form a complete protein
• These shapes allow proteins to function

A system of membrane organelles that are inter-related in their function

How are the organelles of the endomembrane system interrelated?
Take notes on the following slides as your teacher narrates what is happening

What’s up?
How does this design compare to what we have already learned do for the cell?
Well, before we go too me? about me! Sometimes
I’m rough and about protein synthesis?
to make proteins! names.
is always Golgi.
protein synthesis!
Which does give me a complex as well…

http://www.stolaf.edu/people/giannini/ flashanimat/cellstructures/dna.swf
http://www.johnkyrk.com/er.html

How are proteins created by the
“free” ribosomes differ in destination from the proteins created by the
“attached” ribosomes of the ER?
Attached Ribosomes: They make proteins that are either
1) secreted out of the cell
2) attached to the plasma membrane
3) stays enclosed in a membrane to function as another organelle, such as a lysosome.

You will now create a poster of the endomembrane system to demonstrate your understanding of how all the organelles work together.