Lecture2BIO115Winter11d2l - BIO115 Chemical Foundation of...

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Unformatted text preview: BIO115 Chemical Foundation of Biology Jessica Pamment Levels of Biological Organization Levels 1. The biosphere 6. Organs and organ systems 2. Ecosystems 9. Organelles 3. Communities 1 µm 8. Cells 7. Tissues 4. Populations 10. Molecules 5. Organisms Atoms Overview • Elements important to life • Structure of an atom • Chemical bonds in living matter • Properties of water • Acids and bases Chemicals are all around us! ‘Natural’ doesn’t necessarily mean good Naturally occurring toxins in food: • Lectins in raw kidney beans • Solanine by green potatoes/potato shoots • Aflatoxin produced by mold grows on peanuts, raisins, corn What are elements? What are elements? • Organisms are made up of matter • Matter consists of pure elements or compounds • An element can not be broken down to other substances by chemical reactions • 92 occur in nature The Periodic Table of Elements The Periodic Table of Elements Elements Essential for Life • 96% of living matter is made up of: C, O, H, N • Around 4% of remaining weight is made up of: P, S, Ca, and K • Trace elements: B, Cu, I Chemical Composition of the Human Body Carbon (C): 18.5% Oxygen (O): 65.0% Calcium (Ca): 1.5% Phosphorus (P): 1.0% Potassium (K): 0.4% Sulfur (S): 0.3% Sodium (Na): 0.2% Chlorine (Cl): 0.2% Magnesium (Mg): 0.1% Trace elements: less than 0.01% Manganese (Mn) Boron (B) Chromium (Cr) Molybdenum (Mo) Cobalt (Co) Selenium (Se) Silicon (Si) Copper (Cu) Tin (Sn) Fluorine (F) Vanadium (V) Iodine (I) Zinc (Zn) Iron (Fe) Hydrogen (H): 9.5% Nitrogen (N): 3.3% Chemical Composition of the Human Body Chemical Composition of the Human Body (a) Nitrogen deficiency (b) Iodine deficiency The Periodic Table of Elements The Periodic Table of Elements Atomic Structure • Atom is the smallest unit of matter that still retains properties of an element • Subatomic particles: neutrons, electrons, and protons • Atomic number: number of protons 2He • Mass number: sum of protons and neutrons 4He • Atoms neutral in charge have equal number of electrons as protons Isotopes • Different atomic forms of the same element • Isotopes of the same element have the same • Radioactive isotope: nucleus decays number of protons, different number of neutrons spontaneously giving off particles and energy Use of Radioactive Isotopes to detect Alzheimer’s Use of Radioactive Isotopes to detect Alzheimer’s Disease The Role of Electrons • Electron configuration influences the chemical behavior of an atom • Only electrons are directly involved in the chemical reactions between atoms • Electrons are found in different electron shells Atoms of the four elements most abundant in living Atoms of the four elements most abundant in living matter The Role of Electrons • Atoms whose outer shells are not full tend to interact with other atoms • Atoms react with other atoms to try and fill their outer shell • The results is the formation of a chemical bond • Atoms with a full outer shell are unreactive Chemical Bonds, the Glue of Life 1. Ionic bonds 1. Covalent bonds: nonpolar and polar 1. Hydrogen bonds Ionic Bonds • Charge­charge interactions formed between ions • Results from the transfer of electrons between atoms • Compounds formed by ionic bonds are called salts Electron Transfer and Ionic Bonding Na Cl Na Sodium atom Cl Chlorine atom Electron Transfer and Ionic Bonding Na Cl Na Cl Na Sodium atom Cl Chlorine atom Na+ Sodium ion (a cation) Cl– Chloride ion (an anion) Sodium chloride (NaCl) Covalent Bonds • Results from the sharing of electrons • C, H, O, and N are important to life because of their tendencies to form covalent bonds • Nonpolar bonds result between atoms of equal electronegativity • Polar bonds result between atoms of different electronegativity Carbon Carbon Covalent Bonds in Hydrogen Name and Molecular Formula Electrondistribution Diagram Lewis Dot Structure and Structural Formula Spacefilling Model (a) Hydrogen (H2) Covalent Bonds in Water Name and Molecular Formula Electrondistribution Diagram Lewis Dot Structure and Structural Formula Spacefilling Model (c) Water (H2O) Polar Covalent Bonds in a Water Molecule δ– O H H2 O H δ+ δ+ Weak Chemical Bonds • Essential to life due to reversibility • Hydrogen bonds A Hydrogen Bond Water (H2O) δ− δ+ δ δ− Ammonia (NH3) δ δ δ Hydrogen bond Water • Unique properties due to structure • The medium of life, makes life habitable • Exists in solid, liquid, gaseous states • Constitutes 70­95% of cells Hydrogen Bonds between Water Molecules δ– δ+ Hydrogen bond H δ+ δ– δ+ —— δ– O —— H δ+ δ– Properties of Water • Cohesion • Moderation of temperature • Expansion upon freezing • Solvent Cohesion • The tendency for molecules of the same kind to stick together • Water molecules stay together due to hydrogen bonding • Gives water structure • Allows water transport in plants Water Transport in Plants Water-conducting cells Adhesion Direction of water movement Cohesion 150 µm Water strider walking on water Moderation of Temperature • Water acts as a temperature buffer • Energy is needed to break hydrogen bonds before molecules can move faster • Water absorbs and stores large amounts of heat while warming up only a few degrees Oceans can moderate Coastal Climate Santa Barbara 73° Los Angeles (Airport) 75° 70s (°F) 80s 90s 100s Pacific Ocean San Diego 72° 40 miles Burbank 90° San Bernardino 100° Riverside 96° Santa Ana Palm Springs 84° 106° Expansion upon Freezing • Water is less dense as a solid than as a liquid • Water is most dense at 4oC • At 0oC water molecules are locked in a crystal Ice forms an Insulating Barrier Ice Hydrogen bonds are stable Hydrogen bond Liquid water Hydrogen bonds break and re-form Water as a Solvent • Water is a versatile solvent due to polarity of H2O • Water, a solvent, can dissolve ionic compounds (solutes) to make a solution • Water dissolves solutes essential for life –+ Cl– Cl– + – Na+ – – + + – – + – – + + + Na+ – – – Salt dissolving in Water Acids and Bases • Acidic and basic conditions affect living organisms • pH can affect entire communities as well as individual organisms Acids and Bases • Acids increase the [H+] of a solution, thus • decreasing the pH HCL H+ + Cl­ • Bases decrease the [H+] of a solution, thus • • increasing the pH NH3 + H+ NH4+ NaOH Na+ + OH­ The pH The pH Scale Buffers • The internal pH of most living cells is about pH7 • Slight changes in pH affects cellular reactions • Buffers are used to maintain required range • Buffers accept H+ from solution when in excess and donate H+ when depleted Water Quality and the Environment • Alteration of water pH can affect life on earth • Sulfur Oxide from burning fossil fuels leads to acid rain • Carbon dioxide from burning fossil fuels absorbed by oceans produces acid Effects of Acid Rain on a Forest 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 More acidic Acid rain Normal rain More basic Release of volcanic CO Summary • Matter is made up of elements and compounds • 25 out of the 92 elements are essential for life • Oxygen, carbon, hydrogen and nitrogen are the most abundant in living matter Summary • Atom consists of protons and neutrons in the nucleus, and electrons in the shells • Atoms reactivity determined by outer­shell electrons • Strong covalent and ionic bonds, and weaker hydrogen bonds, are essential to life Proton • Positive charge • Determines element Electron • Negative charge • Participates in chemical reactions • Outer-shell electrons determine chemical behavior Nucleus • Consists of neutrons and protons Neutron • No charge • Determines isotope Atom Summary • Water’s polar nature results in H bonds • H bonds are responsible for water’s unusual properties • Most biochemical reactions take place in an aqueous environment • Buffers are essential for pH homeostasis ...
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