Higher Level

Higher LevelNucleic Acid StructureNucleotidesNucleotides are carbon ring structures containing nitrogen linked to a 5-carbon sugar (a ribose)5-carbon sugar is either a ribose or a deoxyriboseIn eukaryotic cells nucleic acids are either:Deoxyribose nucleic acids (DNA)Ribose nucleic acids (RNA)Coding and Non Coding Parts of NucleotidesNon coding Structures= Sugar + Phosphate

Coding Structures= Base SequencesStructure of a Nucleotide

The Phosphate group and the Sugar form the sides of the DNA strand

OHOCH2SugarHHHA Nucleotide

OHNH2NNNNBasePOOHHOOPhosphate23451H+-http://www.zerobio.com/drag_gr9/DNA/dna.htm

Building DNA Video and ActivityNucleotidesThe 4 DNA nucleotidesA & G = PurinesT & C = Pyrimidines

To help you rememberPurines =the Attorney General is PURE

Pyrimidines = have the letter ypYrimidines = thYmine and cYtosine

Purine BasesAdenine and Guanine Double ringed molecular structures

Known as Purine Bases

Pyrimidine BasesThymine and Cytosine

Single ringed structuresKnown as Pyrimidine basesPyrimidinesNH2ONNNHNGuanineNNAdenineNNNH2NONH2NONH2NCytosinePurinesUracil(RNA)CH3NONONHNONONHThymine (DNA)Base NumbersNumber of Purine Bases = Number of Pyramidine Bases

This led to the discovery of Base Pairing NOHNONNHCytosineHONNNNNHHGuanine-+++--Base PairingGuanine And CytosineThree Hydrogen BondsCH3NONONH+-ThymineNNNNHNH-+AdenineBase PairingAdenine And ThymineTwo Hydrogen BondsBase PairingGuanine And ThymineCH3NONONH+-ThymineHONNNNNHHGuanine++-SUGAR-PHOSPHATE BACKBONEHPOHOOOCH2HOHPOOHOOOCH2HPOOHHOOOCH2NH2NNNNOONH2NNHNNNONH2NB A S E SDNAOHPOHOOOCH2HOOH2NNHNNNHHPHOOOCH2OONOH2NNHH2OHOHPOHOOOCH2CH3OOHNNH2O5Phosphate group3Hydroxyl group5Phosphategroup3Hydroxyl groupThe Watson - Crick Model Of DNA3.4 nm1 nm0.34 nmMajorgrooveMinorgrooveA TT AG CC GC GG CT AA TG CT AA TC G------------------------------What have you learnedCan you Outline the simple structure of DNAName the four bases and the base pairs in DNADistinguish between coding and non coding structuresDefine triplet base codeOutline the structure of RNAName the bases in RNADiscuss the replication of DNA

PROTEIN SYNTHESISHigher LevelLesson ObjectivesAt the end of this lesson you should be able to Outline the steps in protein synthesis Understand DNA contains the code for protein Understand that enzymes unwind the DNA Understand this code is transcribed to mRNA Know the role of RNA polymerase Know the role of a codon7. Know the code is translated on the ribosome8. Know the ribosome is composed of subunits9. Understand the amino acids are assembled in the correct order determined by the codons on mRNA to synthesise the protein

Lesson Objectives (cont.)At the end of this lesson you should be able to: 10. Understand a stop codon on mRNA signals the release of the protein11. Know that the protein folds into its functional shape12. Give the location of protein synthesis13. Understand the molecular involvement of DNA, mRNA, tRNA, rRNA and amino acids in the process of protein synthesis

For Protein Synthesis You need:

A supply of amino acids cytoplasm Instructions as how to join the amino acids together genetic codeAn assembly line ribosomesA messenger to carry information from DNA to ribosomes - mRNA

Protein Synthesis - Steps3 stages:

1.Initiation 2. Transcription3.Translation

Remember:DNA RNA ProteinRNA is composed of 3 partsRibose: smaller sugar than deoxyribose of DNAPhosphate4 Nitrogenous Bases A,G,U,C

RNA is single stranded and thus smaller & able to leave the nucleus of the cellDNA RNA Protein NuclearmembraneTranscriptionRNA ProcessingTranslationDNAmRNARibosomeProteinEukaryotic CellTranscriptionTranslation TranscriptionTranslationDNAmRNARibosomeProteinProkaryotic Cell No nucleusDNA RNA ProteinLearning CheckWhat is RNA composed of?

How does RNA (ribonucleic acid) differ from DNA (deoxyribonucleic acid)?

What are the three stages in Protein synthesis?

1. Transcription NuclearmembraneTranscriptionRNA ProcessingTranslationDNAmRNARibosomeProteinEukaryotic Cell1. TranscriptionThe transfer of information in the nucleus from a DNA molecule to an RNA molecule.

Only one DNA strand serves as the template

When complete, mRNA molecule is released into the cytoplasmVideo Clip available in extra material folderTranscriptionTakes places in the nucleus of the cellThe process by which the information from DNA is transferred to RNA. DNA uncoils and unzips.

The exposed DNA bases are matched up with RNA bases in the nucleus to form mRNA.1. Transcription DNAmRNARNA PolymeraseEnzymeA U G G G C U U A A A G C A G U G C A C G U UThis is a molecule of messenger RNA.It was made in the nucleus by transcription from a DNA molecule.

mRNA moleculecodonLearning CheckWhat type of RNA molecule is responsible for taking the DNA copy from the nucleus into the cytoplasmWhat parts of the cell do you find RNA in?Can you outline the stages in transcription?

mRNATakes place in the nucleus of the cellThe process by which the information from DNA is transferred to RNA. DNA uncoils and unzips.

The exposed DNA bases are matched up with RNA bases in the nucleus to form mRNA.Types of RNAThree types of RNA:

A.messenger RNA (mRNA)

B.transfer RNA (tRNA)

C.ribosomal RNA (rRNA)

Remember: all produced in the nucleus!A. Messenger RNA (mRNA)Carries the information for a specific protein.

Made up of 500 to 1000 nucleotides long.

Made up of codons (sequence of three bases)

Each codon is specific for one amino acid.A. Messenger RNA (mRNA)methionineglycineserineisoleucineglycinealanine stopcodonproteinAUGGGCUCCAUCGGCGCAUAAmRNA startcodonPrimary structure of a proteinaa1aa2aa3aa4aa5aa6peptide bondscodon 2codon 3codon 4codon 5codon 6codon 7codon 1B. Transfer RNA (tRNA)Made up of 75 to 80 nucleotides long.

Picks up the appropriate amino acid floating in the cytoplasm

Transports amino acids to the mRNA.

Has anticodons that are complementary to mRNA codons.

Recognizes the appropriate codons on the mRNA and bonds to them with H-bonds.C. Ribosomal RNA (rRNA)Made up of rRNA is 100 to 3000 nucleotides long.

Important structural component of a ribosome.

Associates with proteins to form ribosomes.RibosomesLarge and small subunits.

Composed of rRNA (40%) and proteins (60%).

Both units come together and help bind the mRNA and tRNA.

Ribosomes LargesubunitSmall subunitmRNAAUGCUACUUCGLearning CheckWhat are the three types of RNA?

Where is each type produced?

What is the function of each type of RNA?3. Translation NuclearmembraneTranscriptionRNA ProcessingTranslationDNAPre-mRNAmRNARibosomeProteinEukaryotic CellVideo Clip available in extra material folder3. TranslationSynthesis of proteins in the cytoplasm

Involves the following:1.mRNA (codons)2.tRNA (anticodons)3.rRNA4.ribosomes5.amino acidsTranslationIn the cytoplasm, translation occurs.The mRNA binds to a ribosome.

The strand of mRNA is pulled through the ribosome three bases at a time, in triplets.

Each of these triplets on the mRNA strand is called a codon.A U G G G C U U A A A G C A G U G C A C G U UThis is a molecule of messenger RNA.It was made in the nucleus by transcription from a DNA molecule.

mRNA moleculecodonA U G G G C U U A A A G C A G U G C A C G U UA ribosome on the rough endoplasmic reticulum attaches to the mRNA molecule.ribosomeIt brings an amino acid to the first three bases (codon) on the mRNA.A U G G G C U U A A A G C A G U G C A C G U U Amino acidtRNA moleculeanticodon U A CA transfer RNA molecule arrives.The three unpaired bases (anticodon) on the tRNA link up with the codon.A U G G G C U U A A A G C A G U G C A C G U UAnother tRNA molecule comes into place, bringing a second amino acid. U A C C C GIts anticodon links up with the second codon on the mRNA.A U G G G C U U A A A G C A G U G C A C G U UAnother tRNA molecule brings the next amino acid into place. C C G A A UA U G G G C U U A A A G C A G U G C A C G U UA peptide bond joins the second and third amino acids to form a polypeptide chain. C C G C C GThe polypeptide chain gets longer.

A U G G G C U U A A A G C A G U G C A C G U U G U C A C G The process continues.This continues until a termination (stop) codon is reached.The polypeptide is then complete.tRNA Transfer RNA (tRNA), reads the strand of mRNA and translates it into a strand of amino acids.

A molecule of tRNA has at one end a set of three bases that will complement the mRNA strand; this is called the anticodon.

tRNAIf the 3 base anticodon of the tRNA complements the 3 base codon of the mRNA, they briefly combine.The amino acid is left behind when the tRNA leaves.

As each codon is read, the next tRNA brings in a new amino acid and the polypeptide (protein) chain grows.

This requires enzymes and ATP.

End ProductThe end products of protein synthesis is a primary structure of a protein.

A sequence of amino acid bonded together by peptide bonds.aa1aa2aa3aa4aa5aa200aa199Functional ProteinThe protein now has to undergo folding and the addition of bonds

Folding allows the Protein to reach its 3D (Tertiary Shape) which influences its Function.Learning CheckThe anticodon UAC belongs to a tRNA that recognizes and binds to a particular amino acid.

What would be the DNA base code for this amino acid?Answer:tRNA - UAC (anticodon)mRNA- AUG (codon)DNA - TACWhat have you learned?Can you Outline the steps in protein synthesisUnderstand that a strand of DNA is copied by transcriptionUnderstand the role of mRNAKnow the function of a ribosome in protein synthesisUnderstand the process of translation that leads to the formation of a new proteinKnow that the shape of a protein determines its function End