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

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Presentation on theme: "Protein synthesis: the making of proteins by the cell With the help of RNA."— Presentation transcript:

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

2 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.

3 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

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



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

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

9 3. Ribosomal RNA (rRNA)– makes up part of the ribosome. Helps read mRNAs message and assemble proteins.


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

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

13 2. Translation: Protein is made by adding amino acids to a growing peptide chain. It occurs at the ribosome where proteins are made. Involves mRNA, rRNA and tRNA.

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

15 Protein synthesis in detail. 1.Transcription: mRNA 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

16 Transcription explained in steps: 1. The enzyme RNA polymerase, unwinds DNA and guides the creation of mRNA. 2. The DNA double helix unwinds and separates at a certain point. RNA polymerase uses one strand as a template or model Transcription animation animations/transcription.htm

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

18 RNA DNA RNA polymerase 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) Go to Section:

19 2. Translation mRNA 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 mRNA.

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

21 3. Tranfer RNA or tRNA carries the correct amino acid to the ribosome. It also reads the mRNA codon with rRNA Anticodon: three bases on tRNA that are complimentary to mRNA mRNA codon: UUC tRNA anticodon: AAG

22 4. Amino acids are brought until the entire mRNA is read. Each tRNA 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.


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

25 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.

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

27 Transcription and translation animation dna/transcribe/ Transcription and translation animation wave-nojs.html

28 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.

29 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.


31 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. pH: each protein functions at a specific pH. Increase or decrease can damage it. 3. chemical: exposure to chemicals such as heavy metals

32 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

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

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

35 3. Plug the codons into the chart and find the amino acids. mRNA: AUG-AAC-UUG-AUU Amino acid: met-asp-leu-iso Interactive:


37 . Label the diagram below Go to Section:

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

39 2. Translation: mRNA leaves the nucleus and goes to the ribosome. At the ribosome, a specific protein is made. This is done by tRNA adding amino acids to a growing chain. protein-synthesis protein-synthesis anscription.html anscription.html

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



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

44 Do these on your own: DNA: GCCATTTAACGG mRNA: Amino acid: DNA: AATTCCGGATAT mRNA: Amino acid:

45 DNA: GGCCCTATTGGG mRNA:_________________ Amino acid:__________________ DNA: TACCCCCGATTACGTACC mRNA:__________________________ Amino acid:___________________________

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