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University of Louisville BIO 240 BIO 240 Notes Chapter 2: Chemical Context of Life Bombardier Beetle ( squirts chemicals on ants) Hydro-peroxide and hydroquinone --- defense against predators Exa... mple of a Redox Reaction Matter Na+Cl=NaCl Essential elements (CHONPS) 6 Trace elements – elements needed in tiny amounts but still important, usually in enzymes 92 occurs naturally Atom Nucleus Protons----determine element Neutrons---determine isotope Mass # = Proton + Neutrons Atomic # = Protons Isotopes Same elements w/ diff # of neutrons SAME atomic number DIFF mass number Isotopes important for Carbon dating (figuring out how old something is) based on carbon isotopes Atomic Bomb---use uranium for bombs---Iran & Uranium Enrichment One atom has 7 protons and 7 neutrons. Another atom has 6 protons and 7 neutrons. The two atoms are A. Isotopes of the same elements B. Different Elements C. Have the same atomic number D. A & B are correct E. A, B & C are correct Electrons-determine chemical behavior 1st shell---2e- 2nd shell---8e- 3rd shell---8eetc… energy lost—towards inner shells energy gained—towards outer shells depends on valence electrons Noble gases –already complete shell An element has an atomic number of 6. How many electrons are needed to fill the outer shell? A. 0 B. 2 C. 4 D. 6 E. 8 Covalent bonds -Two atoms sharing a pair of valence electrons -pure element compounds vs molecule - single bond - double bond Electronegativity Attraction of a particular atom for the electrons of a covalent bond Non-polar covalent bond (equal pulling) Polar covalent bond (unequal pulling) Ionic Bond So unequal in valence shell attraction that electron stripped away Bond is formed due to opposite charges Weak Chemical Bonds Hydrogen Bonds What’s the advantage of a weak bond versus a strong bond? Finite amount of energy you don’t want to use all the energy so weak bonds are ideal for this type of reaction. (DNA double helix is held together by hydrogen bonds, but constantly being broken. What type of bond would you predict between two water molecules A. Single Bond B. Polar Covalent Bond C. Ionic Bond D. Hydrogen Bond E. A & D January 11th 2018 -70-80% compositon of living things -polar covalent bonds polar molecule -Hydrogen bonds give water sit 4 properties 4 Properties 1.) Adhesion/Cohesion a. Water falls down and gets picked up and goes against gravity Cohesion: Ability of water to bind to itself Adhesion: Ability of water to bond to other objects Hydrogen bonds allow water to go against gravity 2.) Moderation of Temperature a.) Heat: Kenetic energy transfer Specific Heat: heat gained/lost/ for 1g to change by 1 degree Water has high specific heat - Water in iron on stove Heat breaks hydrogen bonds apart Evaporative cooling Transformation of liquid to gas Evaporation surface cooling Stabilizes our temperatures Effect of high humidity 3.) Expansion upon freezing a. Hydrogen bonds in ice are more ordered ice less dense floating water If ice sank, water would eventually freeze solid, making life impossible Stable hydrogen bonds in ice 4.) Water as versatile solvent Solvent: what’s doing the absorption (water) Solute: what’s being dissolved (sugar) Aqueous Solution When things go into water you get a hydration shell around them Partial negative surrounding the Na, partially positives surrounding Cl (when in water) Nonionic polar molecules (sugars) Large polar molecules with ionic/polar regions (proteins ex: oil) NOT nonpolar molecules! Predict how life on earth would be different if water were LESS polar? A.)Heavier insects that water striders would be able to walk across the surface of a pond B.)Increased cohesion would lead to increased upward water transport in plants C.)Water temperature of ponds and pools would increase more slowly when in sunlight D.) Sweating would be less effective means of keepings cool. What causes an aqueous solution to have an imbalance in H+ and OH-? When acids dissolve in water, they donate additional H+ decrease in pH When bases dissolve in water, they donate OH- which sop up H+ increase in pH The product of H+ and OH- is constant [H+][OH-]=10^-14 pH + pOH=14 H=10-8 pH=8 What is the concentration of OH- ions in a solution where pH=10? A. 1x10^-10 B. 1x10^10 C. 1x10^4 D. 1x10^-4 E. 1x10^7 Strong Acids & Bases Strong acids and bases dissociate completely in water Acid HCl: HClH+Cl- High H+ Base NaOH: NaOHNa+OH Low H+ Weak Acids & Bases are reversible reactions Base Ammonia NH3 Acid Carbonic Acid H2CO3 Most living things cells must remain close to pH 7 Buffer Keeps the pH where it needs to be, keeps solution relatively constant Which of the following is buffered by carbonic acid? A. Bone B. Lung C. Blood D. Intestine E. Skin Carbon Compounds and Life Aside from water, living organisms are mostly carbon-based compounds Inorganic: not made by living things Organic: made by living things Carbon can form 4 covalent bonds, why? -Makes large complex molecules possible Hydrocarbons Organic molecules consisting of only carbon and hydrogen Hydrocarbons can undergo reactions that release a large amount of energy (gasoline) Macromolecules Critically important molecules of all living things Cards, proteins, Nucleic Acids, Lipids Macro-Large Monomers-Small molecules to form Polymer Lipids don’t make polymers, they don’t have monomers Dehydration reaction: Synthesizing a polymer, water is removed and puts 2 molecules together Hydrolysis: Breaking down a polymer, adding H2O to solution How many molecules of water are needed to completely hydrolyze a polymer that is 11 molecules long? A. 8 B. 9 C. 10 D. 11 E. 12 January 18th 2018 Diversity of the polymers Each cell has thousands of diff macromolecules Smalls et of monomers immense variety of polymers Carbohydrates Sugars & Polymers of sugars Polymer- repeaded monomer in a sequence Monosaccharides Multiples of Ch2O Glucose C6H1206 Polysaccarahde Triose-3carbon sugar, Pentose-5 carbon sugar Hexose-6 carbon sugar ex:–fructose & glucose DisaccharideWHICH OF THE FOLLWING IS ONW OF THE PRIMARY CUNCTIONS OF CARBS A. Catalyze chemical reaction B. Energy Storage C. Protect Cell Organelles D. Store Cell’s Information Lipids do not have monomeric units, therefore they do not use dehydration reactions to form larger molecules A. True B. False Lipids do not have monomeric units, therefore they do not use dehydration reactions to form larger molecules A. True B. False Sickle-cell disease is cause by a mutation in the beta hemoglobin gene that changes a charged amino acid, glutamic acid, to valine, a hydrophobic amino acid. This changes the shape and thus the function of the protein. Where in the protein would you expect to find glutamic acid? A. on the exterior surface of the protein B. In the interior of the protein C. Either A or B could be correct According to the endosymbiosis theory, what is the most likely explanation for the origin of the two mitochondrial membranes? A. Both inner and outer membranes were derived from folding of the prokaryotic plasma membrane B. Both inner and outer membranes were derived from folding in of the eukaryotic plasma membrane C. The inner membrane was derived from folding of the prokaryotic plasma membrane and the outer from folding in of the eukaryotic plasma membrane D. The inner membrane was derived from folding of the eukaryotic plasma membrane and the outer from folding in of the prokaryotic plasma membrane Which of the following is a correct distinction between facilitated diffusion and active transport? a) active transport requires conformational changes in the transport protein, and facilitated diffusion does not. b) active transport requires an integral membrane protein to carry out the transport, and facilitated diffusion does not. c) facilitated diffusion requires a protein within the membrane, and active transport does not. d) facilitated diffusion depends on an existing energy gradient acting on the transported substance, while active transport makes such a gradient. e) facilitated diffusion requires cellular energy (usually ATP), but active transport does not. A reaction has a ∆G of –5.6 kcal/mol. Which of the following is most likely to be true? A) The reaction could be coupled to power an endergonic reaction with a ∆G of +8.8 kcal/mol. B) The reaction is not spontaneous. C) To take place, the reaction would need to couple to ATP hydrolysis. D) The reaction would proceed by itself but might be very slow. 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