Biomolecules Lecture Notes PDF

Biomolecules BT10002 Lecture 02-03 Unit One - Foundation L01: January 08 2024 Gopal Chowdhary School of Biotechnology, KIIT University, Bhubaneswar – 751024, India. E-mail: [email protected] Macromolecular Structure Unit-1:...

Biomolecules BT10002 Lecture 02-03 Unit One - Foundation L01: January 08 2024 Gopal Chowdhary School of Biotechnology, KIIT University, Bhubaneswar – 751024, India. E-mail: [email protected] Macromolecular Structure Unit-1: Foundation: Living organisms, prokaryotes and eukaryotes, chemical elements, carbon, small molecules and macromolecules, stereoisomers, chiral compounds. Weak interactions: ionic interactions, hydrogen bond, hydrophobic interactions, van der Waals interactions, hydrophilic, hydrophobic and amphipathic compounds  What is life Water is an integral part of life?????? Prokaryotic Vs Eukaryotic A phylogenetic tree or Evolutionary tree indicating the lines of descent of cellular life on Earth. Monera Protists Fungi Plante Animalia Major elements Vs Trace elements The four most abundant elements in living organisms are hydrogen, oxygen, nitrogen, and carbon. They together make up more than 99% of the mass of most cells. Trace elements The trace elements represent a minuscule fraction of the weight of the human body. They are essential to life, usually because they are essential to the function of specific proteins, including many enzymes. Elemental composition of the human body Biomolecules: are carbon based compounds The chemistry of living organisms is organized around carbon ( >50% of the dry weight of cells. The bonding versatility of carbon was a major factor in the selection of carbon compounds for the molecular machinery of cells during the origin and evolution of living organisms. Covalently linked carbon atoms in biomolecules can form linear chains, branched chains, and cyclic structures. No other chemical element can form molecules of such widely different sizes, shapes, and composition. Biomolecules contain a variety of functional groups Alcohols - one or more hydroxyl groups Amines - amino groups Aldehydes and ketones - carbonyl groups Carboxylic acids - carboxyl groups Many biomolecules are polyfunctional, containing two or more types of functional groups. Biomolecules: Size Small Molecules Mr ̴100 to ̴500 Biomolecules Macromolecules Mr >500 This collection of molecules includes the common amino acids, nucleotides, sugars and their phosphorylated derivatives, and a number of mono-, di-, and tricarboxylic acids. Weak interaction play a critical role in macromolecular structure integrity Weak chemical interactions Covalent bonds—NOT a weak interaction. (G ≈ -200 to -500 kJ/mol) Weak interactions in biological systems. ▪ Hydrogen bonds (G ≈ -8 to -30 kJ/mol) ▪ Ionic bonds (G ≈ -20 to -30 kJ/mol) ▪ Van der waals force (G ≈ -3 to -4 kJ/mol) ▪ Hydrophobic interactions Macromolecules Proteins Proteins are long polymers of amino acids, constitute the largest fraction (besides water) of cells. serve as enzymes, structural elements, signal receptors, or transporters that carry specific substances into or out of cells. Proteome concept Nucleic acids (DNA and RNA) The nucleic acids are polymers of nucleotides. store and transmit genetic information, and some RNA molecules have structural and catalytic roles in supramolecular complexes. Macromolecules Polysaccharides The polysaccharides are polymers of simple sugars such as glucose. They have three major functions: energy-rich fuel stores rigid structural components of cell walls (in plants and bacteria) extracellular recognition elements Macromolecules Lipids water-insoluble hydrocarbon derivatives. structural components of membranes, energy-rich fuel stores, pigments, and intracellular signals. Individual lipid molecules are much smaller (Mr 750 to 1,500) and are not classified as macromolecules. Lipids can associate noncovalently into very large structures (cell membranes). Stereoisomerism Molecules with the same chemical structures/bonds but different stereochemistry—that is, different three-dimensional orientations, the fixed spatial arrangement of atoms are called stereoisomers. Conformational isomers (rotamers) Configurational isomers configurational isomers cannot be obtained by rotating the molecule around a single bond whereas conformational isomers can be obtained by rotating the molecule around a single bond Stereoisomerism: Configurational isomers Configuration is conferred by the presence of either (1) Double bonds (Geometric isomers or cis-trans isomers), or (2) Chiral centers (Optical isomers). They cannot be inter-converted without breaking covalent bonds. Geometric isomers or cis-trans isomers These compounds differ in the arrangement of their substituent groups with respect to the non-rotating double bond (Latin cis, “on this side”— groups on the same side of the double bond; trans, “across”—groups on opposite sides). Stereoisomerism: Configurational isomers A carbon atom with four different substituent is called asymmetric, and asymmetric carbons are called chiral centers. One chiral carbon = two stereoisomers Two or more (n) chiral carbons = 2n stereoisomers Enantiomers : Pairs of stereoisomers that are mirror images of each other. Diastereomers : Pairs of stereoisomers that are not mirror images of each other. In separate solutions, two enantiomers rotate the plane of plane- polarized light in opposite directions. An equimolar solution of the two enantiomers shows no optical rotation - Racemic mixture. Compounds without chiral centers do not rotate the plane of plane-polarized light. Stereoisomerism: Configurational isomers Stereoisomerism: Conformational isomers Conformational isomers (rotamers) They are produced by rotation of carbon- carbon single bonds. They are rapidly interconvertible into each other at room temperature. Example: staggered and eclipsed form of ethane.