LW

BIOL3420-001-Biomolecules-structure and function (1)1

GOALS AND OBJECTIVES

  • Understand structure and function of the most important biomolecules.
  • At the end of the lecture, be able to:
    • Explain the difference between organic and inorganic molecules.
    • Define biomolecules and macromolecules.
    • Explain characteristics and classification of the four main groups of biomolecules.
    • Describe the structure and function of the most important biomolecules, including:
    • Glucose, ribose, deoxyribose, lactose, sucrose, cellulose, triglycerides, phospholipids, cholesterol, amino acids, proteins, DNA, and RNA.

ATOMS, MOLECULES, BONDS

  • Atom: a tiny particle of matter that cannot be subdivided into smaller particles without losing its properties; composed of:
    • Nucleus containing protons and neutrons (mass of atom)
    • Electrons surrounding the nucleus
  • Molecule: two or more atoms bonded together; the smallest unit of a chemical compound.
  • Bond types mentioned:
    • Covalent bond
    • Ionic bond

ORGANIC VS INORGANIC & BIOMOLECULES

  • Organic compounds:
    • Have a backbone of carbon (C) and hydrogen (H).
  • Inorganic compounds:
    • May have C or H, or neither; lack the carbon-hydrogen backbone typical of organics.
  • Biomolecules: compounds produced by living organisms.

MACROMOLECULES

  • Living organisms build macromolecules by linking smaller molecules.
  • Four major groups of biomolecules (macromolecules):
    • Carbohydrates (saccharides, sugars) – general formula: (CH2O)n
    • Lipids
    • Nucleic acids
    • Proteins
  • Macromolecules can contain different types of biomolecules.
  • Polymers: macromolecules that contain numerous monomeric units.

CARBOHYDRATES – MONOSACCHARIDES

  • Contain 3–7 carbon atoms.
  • Pentoses: 5 carbon atoms.
  • Hexoses: 6 carbon atoms.

CARBOHYDRATES – DISACCHARIDES

  • Contain 2 monosaccharide units.
  • Examples:
    • Lactose (Galactose + Glucose)
    • Sucrose (Glucose + Fructose)
  • Structural hints from common structures:
    • Glucose, Galactose, Fructose share the formula for simple sugars with multiple hydroxyl groups.
  • Typical glycosidic linkages (in common disaccharides):
    • Lactose: Galactose β1-4 Glucose
    • Sucrose: Glucose α1-2 Fructose
  • Visual cues from the slide show: each monosaccharide has a carbon skeleton with multiple CH₂OH groups; orientation of bonds (e.g., β linkage) shown in depictions.

CARBOHYDRATES – POLYSACCHARIDES

  • Contain more than 2 monosaccharides.
  • Examples:
    • Cellulose
    • Starch
    • Glycogen
  • Structural and storage roles vary by polymer type and monomer linkages.

CARBOHYDRATES – FUNCTION

  • Structural roles:
    • Cellulose: cell wall in plants and some microorganisms.
    • Peptidoglycan: bacterial cell wall support.
    • Lipopolysaccharides (LPS): present in the outer membrane of Gram-negative bacteria.
    • Capsule polysaccharides: protection/interaction with environment.
  • Other roles:
    • Antibody components (polysaccharide portions can be antigenic).
    • Energy and nutrient source: Glycogen stores energy in animals, fungi, and bacteria.

LIPIDS – TRIGLYCERIDES

  • Storage role: major energy reserve; high energy density.
  • Structure: glycerol backbone esterified to three fatty acids (triglyceride).
  • Saturated vs. unsaturated fatty acids:
    • Saturated: no double bonds; typically straight chains.
    • Unsaturated: one or more double bonds; cis configuration common; introduces kinks preventing tight packing.
  • General representation shows glycerol + three fatty acid chains; variabilities in chain length and saturation affect properties (melting point, fluidity).

LIPIDS – PHOSPHOLIPIDS

  • Structure-function: main components of cell membranes.
  • Typical structure:
    • Glycerol backbone
    • Two fatty acid tails (hydrophobic)
    • Phosphate-containing head group (hydrophilic), often including choline as a head group.
  • Phospholipid bilayer:
    • Polar (hydrophilic) head facing aqueous environments (extracellular and intracellular sides).
    • Hydrophobic (nonpolar) tails form the interior of the bilayer.
  • These properties enable membrane formation and selective permeability.

LIPIDS – STEROIDS

  • Cholesterol: reinforces membranes in animals and some bacteria (mycoplasmas).
  • Ergosterol: sterol component of fungal membranes.

NUCLEIC ACIDS

  • DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
  • Macromolecules built from nucleotides.
  • Sugar components:
    • DNA: deoxyribose
    • RNA: ribose
  • Bases:
    • DNA bases: Adenine (A), Thymine (T), Guanine (G), Cytosine (C)
    • RNA bases: Adenine (A), Uracil (U), Guanine (G), Cytosine (C)
  • Nucleotide structure: sugar + phosphate + nitrogenous base.

NUCLEIC ACIDS – DNA STRUCTURE

  • DNA features:
    • Nitrogenous bases: A, T, G, C
    • Complementary base pairing: A pairs with T; G pairs with C.
    • Backbone: sugar-phosphate chain.
    • Double helix with major groove and minor groove.
    • Strands are antiparallel (5' to 3' on one strand vs 3' to 5' on the other).
  • Directionality markers on strands:
    • 5' end and 3' end labeling.
  • Visual cues from the slide include base pairings and the major/minor groove architecture.

NUCLEIC ACIDS – PRACTICE (CONCEPT)

  • Concept: the sequence of bases in a polynucleotide represents genetic information.
  • Complementarity allows replication and transcription processes.

NUCLEIC ACIDS – DNA VS RNA OVERVIEW

  • DNA: typically two polynucleotide chains (double-stranded).
  • RNA: typically a single polynucleotide chain.
  • Genetic information carriers:
    • DNA is the primary genetic material in almost all organisms.
    • RNA is genetic material in some viruses.
  • The order of bases in a polynucleotide chain encodes genetic information; 3 bases form a codon that specifies a single amino acid in a protein.

PROTEINS

  • Dominant organic compounds in living organisms.
  • Made of amino acids linked by covalent peptide bonds.
  • There are 20 standard amino acids in living organisms.
  • Four levels of protein structure:
    • Primary
    • Secondary
    • Tertiary
    • Quaternary
  • Key terms: AMINO ACID (monomer of proteins).

PROTEINS – STRUCTURAL AND FUNCTIONAL ROLES

  • Structural roles and diverse functions:
    • Can form macromolecules with lipids (lipoproteins) and carbohydrates (glycoproteins).
    • ENZYMES: catalysts of chemical reactions in living organisms.
    • ANTIBODIES: recognize and attach to viruses, bacteria, and other microorganisms.
    • TRANSPORTERS: involved in transmembrane transport and signaling.

PROTEINS – SYNTHESIS AND GENE EXPRESSION

  • Protein synthesis occurs on ribosomes and is mediated by:
    • Transcription: DNA -> messenger RNA (mRNA).
    • Translation: mRNA -> protein, mediated by transfer RNA (tRNA) and ribosomal RNA (rRNA).
  • Key players:
    • DNA (genetic template)
    • mRNA (codons for amino acids)
    • tRNA (brings amino acids to ribosome)
    • rRNA (ribosomal components)

FROM GENE TO PROTEIN

  • Conceptual flow:
    • DNA sequence (gene) contains genetic information.
    • Transcription produces mRNA with codons that encode amino acids.
    • Translation decodes codons into a polypeptide sequence to form a protein.

PROTEIN SEQUENCE TRANSLATION EXAMPLE (DNA TO AMINO ACID SEQUENCE)

  • Given DNA sequence (template 5' to 3' is shown):
    • 5'-ATG GTA GGC GTG ACT GGA ACA CCC TAT AGG GAC ATT TTT TGA-3'
  • Codons (grouped from 5' end):
    • ATG, GTA, GGC, GTG, ACT, GGA, ACA, CCC, TAT, AGG, GAC, ATT, TTT, TGA
  • Translation (standard code):
    • ATG → Methionine (Met)
    • GTA → Valine (Val)
    • GGC → Glycine (Gly)
    • GTG → Valine (Val)
    • ACT → Threonine (Thr)
    • GGA → Glycine (Gly)
    • ACA → Threonine (Thr)
    • CCC → Proline (Pro)
    • TAT → Tyrosine (Tyr)
    • AGG → Arginine (Arg)
    • GAC → Aspartic acid (Asp)
    • ATT → Isoleucine (Ile)
    • TTT → Phenylalanine (Phe)
    • TGA → STOP
  • Resulting amino acid sequence (one-letter and three-letter codes):
    • Met-Val-Gly-Val-Thr-Gly-Thr-Pro-Tyr-Arg-Asp-Ile-Phe-STOP
    • 1-letter: M V G V T G T P Y R D I F *

SUMMARY

  • Four main biomolecule groups: carbohydrates, lipids, nucleic acids, and proteins.
  • Carbohydrates: structural roles (cellulose, peptidoglycan, LPS, capsules) and energy source (glycogen).
  • Lipids: membranes (phospholipids), energy storage (triglycerides), and membrane reinforcement (cholesterol/ergosterol in fungi).
  • Nucleic acids: genetic information carriers; DNA (double-stranded, deoxyribose, A/T, G/C) and RNA (single-stranded, ribose, A/U, G/C).
  • Proteins: diverse roles (enzymes, antibodies, transporters); structure determined by genetic information; synthesis via transcription and translation.
  • The genetic code translates nucleotide sequences into amino acids via codons of 3 bases each.
  • Concrete examples listed throughout: glucose, ribose, deoxyribose, lactose, sucrose, cellulose, triglycerides, phospholipids, cholesterol, amino acids, proteins, DNA, RNA.