Macromolecules of Life

• Lecture discusses macromolecules of life and related concepts.

Agenda

• Six main elements in living organisms
• Monomers, polymers, and biological macromolecules
• Amino acids, peptides, and proteins
• Protein structural hierarchy
• Nucleic acids: DNA and RNA
• Canadian contribution to DNA’s role
• DNA fingerprinting
• Summary of concepts
• Keywords

Learning Outcomes

• Identify the six main elements in living things.
• Name macromolecules (amino acids, proteins, nucleotides, nucleic acids) found in living organisms.
• Understand monomer-polymer relationships for amino acids/proteins and nucleotides/nucleic acids.
• Understand protein structural hierarchy.
• Discuss key features of DNA and RNA molecules and their functions.
• Explain DNA fingerprinting technique.

Main Elements in Living Organisms

• The main elements are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sulfur (S), and phosphorus (P).
• These elements bond to form biological macromolecules that make up structures in cells.
• Carbon is the 15th most abundant element in Earth's crust and 4th most abundant element in the universe by mass.
• Carbon is a primary component of macromolecules: proteins, lipids, nucleic acids, and carbohydrates.
• Carbon can form covalent bonds with up to four different atoms, making it a "backbone" for macromolecules.
• The carbon cycle illustrates carbon movement through living and non-living parts of the environment.

Examples of Macromolecules

• Carbohydrates are composed of simple (sugars) and complex (starches) elements which provide energy.
• Lipids contain phospholipids, sterols, and triglycerides that regulate hormones transmit nerve impulses and store energy as fat.
• Proteins from meat and plants that provide energy, repair tissues, and support growth.

Macromolecules as Polymers

• A monomer is the repeat unit of a polymer.
• Monomers connect to form macromolecules (polymers).
• A polymer is a large molecule with a covalently linked chain of smaller molecules called monomers.
• Polymers are synthetic (created in labs) or natural (created within organisms).

Amino Acids

• Amino acids are building blocks (monomers) of peptides and proteins (natural polymers).
• An amino acid has a central carbon atom bonded to a hydrogen atom, carboxyl group, amino group, and side chain.
• In aqueous medium, carboxyl (-COOH) and amino (-NH2) groups are charged (-COO- and -NH3+).
• There are twenty a-amino acids.
• A peptide bond (C-N) through a condensation reaction joins two identical or different amino acids in a peptide.

Proteins

• Proteins are natural polymers of amino acid monomers and complex structures with twenty different a-amino acids.
• Proteins can be rigid or flexible.
• Proteins functions incldue catalysis, transport, storage, motion, and disease protection.
• Structurally, proteins can be described by sequence of a chain of amino acids (primary), local folding into helices or sheets (secondary), three-dimensional due to side chain interactions (tertiary), and protein with more than one amino acid chain (quaternary).
• Fibrous proteins are tough including structural or storage proteins forming wire-like filaments.
• Fibrous proteins lack tertiary structure, consisting of repeating amino acid sequences and examples include a-keratin, collagens, and elastin.
• Globular proteins that are water-soluble examples of many are enzymes like immunoglobulin, hemoglobin and myoglobulin..

Nucleic Acids

• Nucleic acids are high molar mass essential polymers for protein synthesis including both DNA and RNA.
• DNA contains the largest molecules known, having molar masses of up to tens of billions of grams.
• RNA molecules vary greatly in size up to a molar mass of about 25,000g.
• Nucleic acids contain four building blocks: purines, pyrimidines, sugars, and phosphate groups.
• James Watson and Francis Crick created the double-helical structure for DNA in 1953
• Right-handed double helix is the most stable DNA structure
• DNA has two chains wrapped in a double helix and stabilized by intermolecular forces.
• Each DNA strand of nucleotides consists of a N-containing base, a sugar (2-deoxyribose), and a phosphate group.
• The possibility of storing information is possible by varying the N-containing base
• DNA also contains four nucleoids, which contain the purines adenine (A) and thymine (T) and pyrimidines cytosine (C) and guanine (G).
• Each base can form Hydrogen Bonds in that are very important.
• RNA molecules do not occur as double helices, instead, base-pairing is internal creating strands, loops and bulges.
• RNA usually exists as a single-strand polynucleotide, but special RNA viruses exist that are double-stranded.
• Four N-containing bases found in RNA are adenine (A), cytosine (C), guanine (G), and uracil (U).
• Chemical analysis shows that RNA composition does not obey Chargaff's rules.

RNA Main Functions

• Catalytic RNA (enzyme) drives biochemical reactions (ribozymes).
• Messenger RNA (mRNA) acts as intermediary in protein synthesis.
• Ribosomal RNA (rRNA) forms ribosomes.
• Transfer RNA (tRNA) carries amino acids to the growing polypeptide chain.
• RNA also acts as a modulator of DNA and mRNA interactions and the primary genetic material for viruses.

Canadian Contribution to DNA Role

• In 1944, Oswald Avery reported that the genetic material of the cell was DNA.
• Avery's and his colleagues reports were initially met with skepticism

DNA Fingerprinting

• The human genome has about 3 billion nucleotides which are made of 23 pairs of chromosomes continuously having strands of DNA ranging in length from 50 million to 500 million nucleotides.
• Instructions for protein synthesis stored in genes with about 100,000 genes per protein.
• Contains sequences of bases, repeated several times called minisatellites, which are unique.
• Alec Jeffreys suggested that minisatellite sequences can be a for form identification in 1985.
• With DNA, determining the probability of identical DNA patterns is 1 in 10 billion. The 1st case to convict a person happened in 1987.
• A chemist needs a tissue sample, extracts DNA from the cell and fragments using restriction enzymes in order to make a fingerprint.
• Fragments are separated by electric field gel, transferred to a plastic membrane, and identified by radioactive DNA probes.

Keywords

• Carbon cycle: physical cycle of carbon through Earths systems, including the atmosphere
• Macromolecule: a large, carbon-containing polymer, such as proteins, lipids, nucleic acids, and carbohydrates.
• Polymer: A large molecules consisting of monomers.
• Nucleotide: building blocks of DNA and RNA made of a N-containing base, a sugar, and a phosphate group linked together.
• Amino acid: compound with one amino group (-NH2) and one carboxyl group (-COOH).
• Peptide bond: C-N bond joining two amino acids in a peptide.
• Proteins are the building blocks.
• Proteins are either globular (globe-like) or fibrous (fiber-like).

Milestones in Molecular Informatics

• Avery identified DNA as genetic material in 1944.
• Watson and Crick determined DNA double helix structure in 1953.
• Jeffreys created DNA fingerprinting in 1985.
• The first U.S. case using DNA fingerprints was in 1987.
• The Human Genome project was complete in 2003.