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BY1101 Introduction to Molecular and Cellular Biology

BY1101 Introduction to Molecular and Cellular Biology . Tutorial for module BY1101: Proteins and nucleic acids Joe Colgan ( tcolgan@tcd.ie ). BY1101 Introduction to Molecular and Cellular Biology . Tutorial objectives. Describe polymeric biological molecules

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BY1101 Introduction to Molecular and Cellular Biology

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  1. BY1101 Introduction to Molecular and Cellular Biology Tutorial for module BY1101: Proteins and nucleic acids Joe Colgan (tcolgan@tcd.ie)

  2. BY1101 Introduction to Molecular and Cellular Biology Tutorial objectives • Describe polymeric biological molecules • Describe structure and functions of proteins • Describe structure and functions of nucleic acids

  3. BY1101 Introduction to Molecular and Cellular Biology Major classes of molecules • What are the four major classes of molecules of life? Carbohydrates Lipids Proteins Nucleic acids

  4. BY1101 Introduction to Molecular and Cellular Biology What is a polymer? • Long molecule consisting of similar or identical monomers linked by covalent bonds • Examples: • Polymer: Protein • Monomer: Amino acid • Polymer: Nucleic acid • Monomer: Nucleotide

  5. BY1101 Introduction to Molecular and Cellular Biology Polymeric biological molecules How are polymers formed? How are polymers broken down? Dehydration reaction Hydrolysis

  6. BY1101 Introduction to Molecular and Cellular Biology • What is a protein? • Large molecules or polymers consisting of amino acids • One or more polypeptides each folded and coiled in a 3D structure

  7. BY1101 Introduction to Molecular and Cellular Biology What types of proteins are there? EnzymesReceptor Contractile/motorHormonal StructuralTransport DefensiveStorage

  8. BY1101 Introduction to Molecular and Cellular Biology What is an amino acid? A monomer that forms peptide bonds with other amino acids to create a polypeptide An organic molecule consisting of an amino, carboxyl and R-group R-group Side chain R2 R1 Amino Carboxyl H3N H3N CH COO CH COO Peptide backbone α-Carbon H H H2O Hydrogen -> Peptide bonding through dehydration reaction -> Peptide breakdown through hydrolysis

  9. BY1101 Introduction to Molecular and Cellular Biology Subgroups of amino acids How many naturally occurring amino acids are there? 20 4 subgroups

  10. BY1101 Introduction to Molecular and Cellular Biology

  11. BY1101 Introduction to Molecular and Cellular Biology Protein synthesis Transcription of mRNA Migration of mRNA Translation of protein

  12. BY1101 Introduction to Molecular and Cellular Biology Protein synthesis 20 amino acids 4 possible nucleotide bases 3 nucleotides = 1 codon 1 codon = 1 amino acid

  13. BY1101 Introduction to Molecular and Cellular Biology Protein structure Primary structure • Primary structure • A linked series of amino acids with a unique sequence • Function: • Dictates secondary and tertiary structure due to: • Chemical nature of the backbone • R-side chains

  14. BY1101 Introduction to Molecular and Cellular Biology Protein structure What are the defining characteristics of the secondary structure of proteins? Secondary structure Coils and folds repeatedly present within a polypeptide chain Result from hydrogen bonds forming between repeating constituents of the polypeptide backbone Two main structures: Alpha helix: Delicate coil held together by hydrogen bonding at every fourth amino acid Beta-pleated sheets: Form by hydrogen bonds between two parallel parts of polypeptide backbone

  15. BY1101 Introduction to Molecular and Cellular Biology What are the defining characteristics of the tertiary structure of proteins? Tertiary structure Tertiary structure Shape of a polypeptide resulting from interactions within the side chains (R Groups) of various amino acids

  16. BY1101 Introduction to Molecular and Cellular Biology Quaternary structure Overall protein structure that results from the aggregation of multiple polypeptide subunits

  17. BY1101 Introduction to Molecular and Cellular Biology Protein structure summary Primary structure: sequence of a chain of amino acids • Secondary structure: when the sequence of amino acids • are linked by hydrogen bonds • α-helix: bonds every 4 aa • β-pleated sheet: parallel polypeptides • (note: bonds occur in polypeptide backbone ) • Tertiary structure: attractions between  helices and  sheets •   irregular loops and folds that give overall 3D shape • chaperones help with the folding • (note: interactions occur between side chains eg. hydrophobic) Quaternary structure: when more than one amino acid chain is present

  18. BY1101 Introduction to Molecular and Cellular Biology How does the structure links to function? e.g. A single amino acid substitution can cause sickle-cell disease as red blood cells will become less flexible which results in a reduced capacity to carry oxygen. Symptoms: pain, serious infections, chronic anemia and damage to body organs.

  19. BY1101 Introduction to Molecular and Cellular Biology Nucleic acids

  20. BY1101 Introduction to Molecular and Cellular Biology What are nucleic acids? • Large macromolecules essential for life • What are the two types of nucleic acids? • Deoxyribonucleic acid (DNA) • Ribonucleic acid (RNA) • What are the roles of nucleic acids? • Storage of genetic information • Transmission of genetic information • DNA -> RNA -> Protein

  21. BY1101 Introduction to Molecular and Cellular Biology Components of nucleic acids Deoxyribonucleic acid (DNA) Pyrimidines Cytosine (C) Thymine (T) Purines Adenine (A) Guanine (G) Nitrogenous base Phosphate group Sugar molecule

  22. BY1101 Introduction to Molecular and Cellular Biology Ribonucleic acid (RNA) DNA vs RNA Single stranded Different sugars (Deoxyribose vs. ribose) 3. Uracil replaces thymine

  23. BY1101 Introduction to Molecular and Cellular Biology Structure of nucleic acids

  24. BY1101 Introduction to Molecular and Cellular Biology Nucleic acids and proteins • Both polymers • Both essential for life • Nucleic acids encode for protein sequence • Proteins are also involved in cellular processes • Mutations in nucleic acid sequence can result in changes at the protein level

  25. BY1101 Introduction to Molecular and Cellular Biology Past paper questions Exam 2011 Exam 2008

  26. BY1101 Introduction to Molecular and Cellular Biology Past paper questions 2010 2. Write an essay entitled ‘Polymeric Biological Molecules’ 2008 2. Discuss which you think is the more important for life: DNA or protein

  27. BY1101 Introduction to Molecular and Cellular Biology Questions Further reading: Campbell Chapter 5

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