Protein synthesis the making of proteins by the

Protein synthesis: the making of proteins by the cell With the help of RNA

So far we’ve discussed one type of nucleic acid: DNA • A second type of nucleic acid is RNA. • Like DNA, RNA is made up of three nucleotides. 1. A five carbon sugar, 2. a phosphate and 3. a nitrogenous base.

• The five carbon sugar of RNA is called ribose. • The phosphate group is the same as DNA • RNA also has four bases except it lacks thymine. • It has a base called uracil instead of thymine. • Uracil pairs with adenine. • U-A

In all, there are three differences between RNA and DNA RNA 1. Ribose sugar DNA Deoxyribose sugar 2. Uracil as a base Thymine as a base GCAU GCAT 3. Single strand Double strand

• There are three types of RNA molecules. • Each has a different function in making or synthesizing proteins. 1. Messenger RNA (m. RNA) – carries DNAs message from the nucleus to the ribosome.

2. Transfer RNA (t. RNA)– carries the correct amino acids to the ribosome so they can be added to the growing protein chain.

3. Ribosomal RNA (r. RNA)– makes up part of the ribosome. Helps read m. RNAs message and assemble proteins.

There are two steps in protein synthesis. 1. Transcription 2. Translation

Two steps to protein synthesis 1. Transcription – m. RNA is made from the DNA code. • It occurs in the nucleus where the DNA is located. • Involves DNA and m. RNA

2. Translation: Protein is made by adding amino acids to a growing peptide chain. It occurs at the ribosome where proteins are made. • Involves m. RNA, r. RNA and t. RNA.

Making Proteins DNA: DNA TAC CGA TCG TGA ACT Transcription m. RNA: AUG GCU AGC ACU UGA Translation Protein: Met-Ala-Ser-Thr-Stop

Protein synthesis in detail. 1. Transcription: • m. RNA is made from the DNA code in the nucleus • The entire DNA code is not copied. • Just one gene segment that codes for a specific protein

Transcription explained in steps: 1. The enzyme RNA polymerase, unwinds DNA and guides the creation of m. RNA. 2. The DNA double helix unwinds and separates at a certain point. • RNA polymerase uses one strand as a template or model Transcription animation http: //www. fed. cuhk. edu. hk/~johnson/teaching/genetics/ animations/transcription. htm

3. Nucleotides are added into a complimentary strand of m. RNA based on the DNA code. • DNA: AATTGGCAC • m. RNA: UUAACCGUG 4. This m. RNA strand leaves then nucleus and goes to the ribosome for translation

TRANSCRIPTION: label the diagram Section 12 -3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase RNA Go to Section: DNA

2. Translation • m. RNA is now at the ribosome where amino acids are added to make a long protein chain. • Its still based on the DNA code which is carried by m. RNA.

Translation explained in steps 1. The m. RNA is read by r. RNA. • r. RNA makes up the ribosome. 2. m. RNA is read three bases at a time. • Every three bases on m. RNA codes for one amino acid and is called a codon. Codon: Three bases on m. RNA that codes for one amino acid.

3. Tranfer RNA or t. RNA carries the correct amino acid to the ribosome. It also reads the m. RNA codon with r. RNA Anticodon: three bases on t. RNA that are complimentary to m. RNA • m. RNA codon: UUC • t. RNA anticodon: AAG

4. Amino acids are brought until the entire m. RNA is read. • Each t. RNA drops off one amino acid then goes into the cytoplasm to grab another. 5. The ribosome bonds each amino acid together using a peptide bond creating a polypeptide. • Eventually the stop codon is reached and the final amino acid is added.

1. Single amino acid 2. Growing polypeptide chain bonded with peptide bonds 3. Transfer RNA carrying amino acids 4. Part of m. RNA 5. The ribosome is made of r. RNA and proteins.

6. Finally, the protein is shipped to the golgi body where it is altered and shipped to where it needs to go. 7. At its final destination, the protein will perform the job it was created to do.

HOW DOES RNA POLYMERASE KNOW WHERE TO START • m. RNA has a start codon, a specific three letter nucleotide sequence that says begin here. • The start codon on m. RNA is the three letters AUG • Remember how big DNA is. • The entire molecule is not used to make m. RNA. Just a small portion. • A stop codon tells RNA polymerase to stop making the protein.

Transcription and translation animation http: //learn. genetics. utah. edu/content/begin/ dna/transcribe/ Transcription and translation animation http: //www. pbs. org/wgbh/aso/tryit/dna/shock wave-nojs. html

• Your body is made mostly of proteins. • Your skin pigments are proteins. • Part of you blood and vessels are made of proteins. • Your muscles, brain, enzymes, etc are all made partly of proteins. • Your ribosomes are continuously making them. • You have thousands in each cell of your body.

Several factors determine the differences between all the proteins in your body. 1. the order of amino acids: you change the order and you change the protein and its function. 2. shape of the protein: the golgi shapes the protein after its assembled. You change the shape, you change the protein and function. Denature: The shape of a protein is changed and it stops working.

Several things can cause a protein to denature 1. heat: each protein function at a specific temperature. • Heat changes the shape, therefore changes function. • High fevers can be dangerous to your body. 2. p. H: each protein functions at a specific p. H. • Increase or decrease can damage it. 3. chemical: exposure to chemicals such as heavy metals

• One skill you need for the regents exam is to create a protein when given a DNA code. • You will need to use this amino acid chart Remember the bases for • DNA are GCAT • RNA are GCAU

1. When given a DNA code, you must first transcribe it into m. RNA • Do this by complimentary base pairing. A-U G-C DNA: TACTTGAACTAA m. RNA: AUGAACUUGAUU

2. Next break the m. RNA into codon or three letters. DNA: TACTTGAACTAA m. RNA: AUGAACUUGAUU m. RNA: AUG-AAC-UUG-AUU This particular m. RNA was broken into four codons. How many amino acids will this protein be?

3. Plug the codons into the chart and find the amino acids. • m. RNA: AUG-AAC-UUG-AUU • Amino acid: met-asp-leu-iso • Interactive: http: //www. learner. org/interactives/dna/engineering 4. html

64 POSSIBLE CODONS

Label the diagram below. Go to Section:

Summary of protein synthesis: • Protein synthesis takes place in 2 steps: • Transcription and translation 1. Transcription: • DNA unzips • m. RNA is made by complimentary base pairing • Happens in the nucleus.

2. Translation: • m. RNA leaves the nucleus and goes to the ribosome. • At the ribosome, a specific protein is made. • This is done by t. RNA adding amino acids to a growing chain. • http: //www. edumedia-sciences. com/en/a 71 protein-synthesis • http: //library. thinkquest. org/20465/g_DNATr anscription. html

Making Proteins DNA: DNA TAC CGA TCG TGA ACT Transcription m. RNA: AUG GCU AGC ACU UGA Translation Protein: Met-Ala-Ser-Thr-Stop

GCC: AUG: UUU: : ACG: CGU: TTT:

CCC: GCA UUU AUG AGG AAA CGC ATG:

• Starting with DNA, find the m. RNA code, and the amino acid sequence using one of the charts. • • • DNA: ATATTTGCCGAA m. RNA: UAU-AAA-CGG-CUU t. RNA: AUA-UUU-GCC-GAA Amino acid: Tyr-Phe-Ala-Glu Use m. RNA in the amino acid chart

Do these on your own: DNA: GCCATTTAACGG m. RNA: Amino acid: DNA: AATTCCGGATAT m. RNA: Amino acid:

• DNA: GGCCCTATTGGG • m. RNA: _________ • Amino acid: _________ • DNA: TACCCCCGATTACGTACC • m. RNA: _____________ • Amino acid: ______________