BY1101 Introduction to Molecular and Cellular Biology Tutorial for module BY1101: Proteins and nucleic acids Joe Colgan

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

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

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 BY1101 Introduction to Molecular and Cellular Biology

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

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

BY1101 Introduction to Molecular and Cellular Biology What types of proteins are there? Enzymes Receptor Contractile/motor Hormonal Structural Transport Defensive Storage

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 H3NH3N COO CH R1R1 H2OH2O H H3NH3N COO CH R2R2 H Amino Carboxyl R-group Hydrogen α-Carbon Side chain Peptide backbone -> Peptide bonding through dehydration reaction -> Peptide breakdown through hydrolysis

BY1101 Introduction to Molecular and Cellular Biology Subgroups of amino acids How many naturally occurring amino acids are there? 20 4 subgroups PolarHydrophobicGlycine (G), Alanine (A), Valine (V), Isoleucine (I), Leucine (L), Phenylalanine (F), Methionine (M), Proline (P), Tryptophan (W) Non-PolarHydrophilic (Neutral)Serine (S), Threonine (T), Tyrosine (Y), Cysteine (C), Asparagine (N), Glutamine (Q) Non-PolarHydrophilic (Acidic)Aspartic acid (D), Glutamic acid (E) Non-PolarHydrophilic (Basic)Lysine (K), Arginine (R), Histidine (H)

BY1101 Introduction to Molecular and Cellular Biology

Protein synthesis Transcription of mRNAMigration of mRNATranslation of protein

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

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

BY1101 Introduction to Molecular and Cellular Biology Protein structure 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 Secondary structure Coils and folds repeatedly present within a polypeptide chain Result from hydrogen bonds forming between repeating constituents of the polypeptide backbone What are the defining characteristics of the secondary structure of proteins?

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

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

BY1101 Introduction to Molecular and Cellular Biology 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 Protein structure summary

How does the structure links to function? BY1101 Introduction to Molecular and Cellular Biology 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.

BY1101 Introduction to Molecular and Cellular Biology Nucleic acids

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

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

BY1101 Introduction to Molecular and Cellular Biology Ribonucleic acid (RNA) DNA vs RNA 1.Single stranded 2.Different sugars (Deoxyribose vs. ribose) 3. Uracil replaces thymine

BY1101 Introduction to Molecular and Cellular Biology Structure of nucleic acids

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

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

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

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