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Transcript
Macromolecules and Cells Molecular biology of the cell and cell theories Atoms e P e e e Hydrogen atom (H) 6P 6N e e Carbon atom (C) e Bonds form Molecules molecule: two or more atoms chemically bonded together • Ionic bonds are formed between atoms that become oppositely charged. The charged atoms are ions, which are formed after donating or accepting electrons. Example: NaCl • Covalent bonds are formed when electrons are shared between atoms. H-H indicates single covalent bond whereas O=C indicates double bond • Hydrogen bonds result from attraction between partial charges of different molecules. Carbohydrates Example: Glucose, C6H12O6 (chemical formula) H-C=O H-C-OH OH-C-OH H-C-OH H-C-OH H-C-OH H Glucose molecule folds into a 6-sided shape (hexagon) Because it has 6 carbons it is called a hexose sugar Carbohydrates Pentose sugars • Ribose: C5H10O5 – Found in RNA • Deoxyribose: C5H10O4 – Found in DNA Carbohydrates Monosaccharides • Glucose • Fructose • Galactose • Ribose Disaccharrides • Lactose • Maltose • Sucrose + synthesis reaction Polysaccharides Lipids • Mostly insoluble in water • Large sections of hydrocarbon (with few oxygens) are hydrophobic • Fatty acid: COOHCH2CH2CH2CH2… • Can bind to other macromolecules such as glycerol (below) H H-C-OH COOHCH2CH2CH2CH2… H-C-OH COOHCH2CH2CH2CH2… H-C-OH COOHCH2CH2CH2CH2… H triglyceride Phospholipids • Consists of two fatty and a phosphate (PO4) acids attached to a glycerol molecule Phosphate head is hydrophilic Fatty acid tails are hydrophobic Amino Acids • The building blocks of proteins Amino group H O H N C H R C OH Variable group Carboxylic acid group Proteins • Primary structure is a chain of amino acids • Can fold into secondary and tertiary structures • Protein subunits can combine to form quaternary structure AA AA AA AA AA Protein synthesis: formation of primary structure of protein. Complex process that involves ribosomes, tRNA, mRNA, and DNA Secondary and tertiary structures Helical shapes What do proteins/polypeptides do? • • • • • Some are Enzymes, catalysts for reactions Some are important in regulation/communication Some help maintain structure Some are infectious agents called Prions Proteins are expressions of genes and help make up phenotypic characteristics of organisms Gene RNA Protein Nucleotides • • • • • • Consist of nitrogenous base +pentose sugar+ phosphate Nucleotide monophosphate (NMP): 1 phosphate Nucleotide diphosphate (NDP): 2 phosphates Nucleotide triphosphate (NTP): 3 phosphates Exist for all nitrogenous bases: A, G, T, C,U Nucleotides are high energy compounds and building blocks for nucleic acids (DNA and RNA) • Pentose sugar in RNA is ribose and in DNA is deoxyribose • Nucleotides with deoxyribose are dNTP Nucleotides • Nitrogenous bases : Adenine, Guanine, Cytosine, Thymine, and Uracil (RNA only) Nitrogenous base (adenine) P Pentose sugar P P Phosphates and high energy bonds Nucleic acids • RNA: ribonucleic acid • DNA: deoxyribonucleic acid • Primary structure consists of chain (strand) of nucleotides linked from sugar to phosphate • Can be single stranded or double stranded • Can fold into many secondary and tertiary structures including helices • Both DNA and RNA can be hereditary material of microorganisms Single stranded nucleic acid NTP Double stranded nucleic acid Nitrogenous bases protrude from the sugar phosphate backbone like rungs of a ladder Short piece of DNA is called an oligonucleotide Nucleic Acids Nitrogenous bases that protrude from the sugar phosphate backbone form hydrogen bonds between two strands of nucleic acid Base pairing occurs as follows: DNA 5’…ACTGCT…3’ 3’…TGACGA…5’ RNA 5’…ACUGCU…3’ 3’…UGACGA…5’ 2 hydrogen bonds between A and T 3 hydrogen bonds between C and G Complex Biomolecules • • • • • • • • • Usually assembled inside cells by enzymes Glycolipids Lipoproteins Glycoproteins Nucleoproteins (ribosomes) Peptidoglycan (bacterial cell wall) Lipopolysaccharide (outer membrane of bacteria) Many other types Note: as we will see later, many of these can be antigens stimulate an immune response Ribosomes 21 different proteins 16SrRNA 30S subunit 31 different proteins 70S ribosome (prokaryotes) 50S subunit 23S rRNA and 5S rRNA Membranes • Made of phospholipid bilayers, proteins, and other complex biomolecules • When formed into a spherical shape, can become a vessel for hereditary material • Vary in complexity and composition depending on the type of organism • May play a vital role in the survival of organisms Phospholipid bilayer Intracellular Extracellular Theories about cells • Cell theory: cells are the basic units of all living things • ‘Primordial Soup’ Theory – A separate, but complementary theory to evolution – Occurred over millions or billions of years – Organic molecules formed from the highly reducing atmosphere of early earth in an aqueous environment – The earliest cells coalesced from organic molecules by the inclusion of autocatalytic molecules within simple lipid micelles or droplets • Endosymbiont theory: organelles such as mitochondria evolved from living organisms Variation in Bacterial Cell Structure • Cell morphology (size and shape) • Cell membranes (inner and sometimes an outer) • Cell wall (most of the time) • Accessory structures (e.g. flagella, fimbriae) Diversity of Structure in Microorganisms Nucleic acid Viruses Protein coat (capsid) Membrane and spikes Circular DNA Prokaryotes membrane peptidoglycan membrane Eukaryotes organelles DNA contained within nucleus Variation in bacterial cell wall structure Gram-positive bacteria have thick layer of peptidoglycan which often contains teichoic acid Gram-negative bacteria have thinner cell wall but have lipopolysaccharide in an outer membrane Acid-fast bacteria have cell wall similar to G+, but lots of lipid and less peptidoglycan Mycoplasmas lack cell wall Variation in Bacterial Cell Walls Cell wall bilayer LPS Prokaryotes Eukaryotes DNA not contained within a membranous nucleus DNA in form of linear chromosomes Chromosome is circular piece of DNA May contain plasmids (small circular DNA) Contain ribosomes but generally lack membranous organelles DNA inside of nucleus DNA contains introns and exons Contain variety of membranous and nonmembranous organelles May be single-celled or multicellular