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Atoms, Molecules and Macromolecules Building Complex Molecules That Comprise Living Things Prof. Mary Colavito & Dr. John Shepanski Comparison of Terms Element Atom Molecule Substance that cannot be broken down to another substance with different properties Smallest unit that has characteristic properties of the element Two or more atoms joined by chemical bonds Macromolecule Large polymer made of monomer units Composition of an Atom • Nucleus Proton = positively charged particle (+) Neutron = uncharged particle (n or +) Number of protons + Number of neutrons = Atomic mass Number of protons = Atomic number •Electrons = negatively charged particles Number of electrons = Number of protons Each electron circles the nucleus in an orbit representing a specific energy level. 12 6 C Atomic Models Electron Shell Nucleus Hydrogen (H) Helium (He) Different Kinds of Atoms Innermost electron shell 8e- + 8n 8p Oxygen Max 2e2e- + 2n 2p +2p+ +2n± +2e+7p+ +8n± +7e- Max 8e- +4p+ Helium +4n± +4e- 15e- + 16n 15p +5p+ +4n± +5e Phosphorus 6e- + 6n 6p Carbon 20e- + 20n 20p Calcium http://www.sciencegeek.net/tables/lbltable.pdf Electron Energy Levels Energy Level Capacity for Electrons 1 2 3 2 8 18 (8*) *In forming molecules, atoms combine to fill their outer (valence) energy levels. When 8 valence orbitals are filled, remaining, unused slots available in inner levels are filled before a new valence shell is added. Chemical Bonds Bond Ionic Characteristics One atom loses an electron, another gains an electron Covalent Atoms share electrons Electrons are shared Polar unequally Covalent Hydrogen Covalently-bound hydrogen is attracted to another atom Positive charge Ionic Bonding in NaCl – – – – – – +±+ + ++±± ± ± + ± + ±±± + – – – – – – – Sodium – – – – – – – – – – – – – – – – – +±+ + ++±± ± ± + ± + ±±± + – – Electron Completely Transferred – – – #electrons=10 – – +±+ + ++±± ± ± + ± +±± ± + – Sodium ion #electrons=11 – – – – Chlorine #electrons=17 – – – – – – +±+ + ++±± ± ± + ± + ±±± + – – – – – – – – Negative charge – Chlorine #electrons=18 Ionic Bonding in NaCl • Ion: charged atom with unequal numbers of protons and electrons. • Ions of opposite charges attract. • Sodium ions nestle between chlorine ions. • Perfectly cubical crystals form. Cl- +Cl- +Cl- +Cl- Na Na Na Na+ Cl- +Cl- +Cl- +Cl- + - ClNa Na - Na - Na Cl Cl Cl Na-+ Cl Na+ Na+ Na+ Cl- + Cl- +Cl + - Na+ Na Na Na ClCl Cl Cl Na-+ Cl Na-+ Na+ Na+ Cl- +Cl- +Cl + - Na+ Na Na Na Cl Cl Cl ClNa+ Na+ Na+ Na+ - Cl- Cl- Cl +Cl Na Na+ Na+ Na+ Covalent Bonding Oxygen Atom Oxygen Atom Oxygen Molecule (O2) In Water, Polar Covalent Bonds Join Oxygen and Hydrogen Hydrogen Bonds Join Water Molecules Water molecules are dipoles—the hydrogen side is more positive; the oxygen side is more negative Hydrogen bonds form between O of one water molecule and H of another H H + – O + H + O – + H + Hydrogen Bonds Due to hydrogen bonding, ionic and polar substances dissolve in water Organic Molecules Contain Carbon Each carbon atom can make four covalent bonds with other types of atoms or additional carbons. Hydrophobic Not attracted to water & non-polar substances Hydrophilic Attracted to water, polar and ionic substances Macromolecules: Polymers Made of Repeating Monomers Macromolecule Monomer Unit Carbohydrates Sugars Lipids Proteins Fatty acids Amino acids Nucleic Acids Nucleotides Synthesis and Breakdown of Macromolecules Condensation Synthesis Hydrolysis Removal of water to add monomer units Addition of OH and H groups of water to break a bond between monomers Dehydration Synthesis / Hydrolysis Dehydration Synthesis Hydrolysis Carbohydrates: Structure • Simple – Monosaccharides= one sugar unit Glucose = blood sugar All cells use glucose for energy Carbohydrates: Structure • Simple – Disaccharides = two sugar units – Examples: sucrose, lactose, maltose CH2OH HOCH2 O H O H H + H H HO OH H CH2OH HO OH HO HO H H HO Glucose + Fructose CH2OH H HOCH2 O O H H H HO H OH H O HO CH2OH H H HO HOH HO Sucrose & Water Carbohydrates: Structure • Complex – Polysaccharides= many sugar units • Starch -- storage in plants • Glycogen -- storage in animals • Cellulose -- plant cell walls, indigestible Carbohydrates: Structure • Complex – Polysaccharides= many sugar units found in plant cell walls energy storage in plants energy storage in animals Carbohydrates: Functions • Energy source • Structural component • Cell-cell communication Lipids: Structure • Phospholipid—component of cell membranes Polar Head Glycerol Hydrophilic Fatty Acid Tails Hydrophobic Lipids: Structure • Types of Fatty Acids – Saturated – 2H per internal carbon – Unsaturated -- <2H per internal carbon one or more double bonds • Monounsaturated – one double bond • Polyunsaturated – more than one double bond Which Is a Source of Unsaturated Fatty Acids? Linseed Oil Beef Fat Lipids: Functions • Concentrated energy source • Structural components of cell membranes – Phospholipids – Cholesterol • Communication – Steroid Hormones • Metabolism – Fat-soluble vitamins • Insulation Cholesterol • Protection from water Phospholipids – Waxes Per 23 chromosomes Now estimated at 30,000 genes Information Flow From DNA replication (before cell duplicates) Gene: sequence of DNA that codes for a protein DNA transcription (ongoing parts of cell metabolism) RNA translation Protein DNA and RNA Structure Primary Structure Secondary Structure DNA RNA Chain of nucleotides Double helix Chain of nucleotides Single folded chain Nucleotide = phosphate + sugar + nitrogen-containing base DNA Replication •DNA chains separate •Each chain is used as a pattern to produce a new chain •Each new DNA helix contains one “old” and one “new” chain Transcription = Production of RNA Using DNA as a Template •DNA chains separate •ONE DNA chain is used as a pattern to produce an RNA chain •RNA chain is released and the DNA chains reform the double-helix In DNA In RNA A U T A G C C G Transcription Protein Synthesis • Messenger RNA Contains the code words for the sequence of amino acids in a specific protein CODON = group of three nucleotides acting as a code word for a protein amino acid • At sub-cellular structures called ribosomes, RNA code is used to guide the assembly of proteins Four Levels of Protein Structure Tertiary Primary (Sequence) (Folding by R-group interactions) Quaternary (Two or more chains associating) Secondary (Coiling by Hydrogen Bonding) Proteins: Structure • Primary structure = chain of amino acids – Amino acids have common features Carboxylic Acid Group Amino Group R Central Carbon The “R” Group Differs for Each Amino Acid Proteins: Structure Forming the Protein Chain Phenylalanine Leucine Dehydration Synthesis between COOH & NH2 Secondary structure governed by hydrogen bonds Tertiary structure governed by attraction/repulsion of R-groups Four Levels of Protein Structure • Quaternary Structure: Association of two or more protein chains eg. Hemoglobin is composed of 4 protein chains 2 are called alpha hemoglobin 2 are called beta hemoglobin Cell Membrane The Cell Tissues & Organs Lung Tissue Neurons The Brain The Most Complex Assembly Of Matter Of Which We Know