Life 102 Exam 1 CSU Arthun Questions & Answers Already Graded A+

At what organizational level is life's uniformity most evident? - Answer-Most evident in cells At what organizational level is life diversity most evident? - Answer-Most evident in organisms How do Atoms fill their Valence shell? - Answer-Donate or accept electrons from another atom or two atoms can share an electron pair creating a covalent bond. What happens when an atom gains or loses an electron? - Answer-It becomes ionic 96% of living mater is composed of which elements? - Answer-Carbon, Nitrogen, Hydrogen, Oxygen (HONC) How can you distinguish one element from another? - Answer-By the number of protons What are isotopes? - Answer-Isotopes are the same element, with a different number of neutrons. How do isotopes differ? - Answer-Based on their number of neutrons What is a covalent bond? - Answer-A covalent bond is when two atoms share an electron pair What is the difference between a polar and non-polar covalent bond? - Answer-Polar covalent bond electrons are not equally shared between the two atoms, non-polar are equally shared How do atoms share a pair of electrons? - Answer-Through covalent bonds What effect does the sharing of a pair of electrons have on their valence shells? - Answer-They can fill their valence shellsHow many electrons does it take to fill the valence shells of C, H, O, N - Answer-Carbon-4 Nitrogen-3 Oxygen-2 Hydrogen-1 Why are hydrogen bonds important for biological molecules? Example of a biological molecule that contains hydrogen bonds - Answer-They are important because due to them water has a high heat of vaporization, it will cause a high specific heat as we. It is also important for giving stabilization without permanent bonds. DNA is an example of a biological molecule containing hydrogen bonds What does mass conservation law state? - Answer-Mass can be changed from one form to another but the overall mass does not change (number of molecules doesn't change) What does it mean when a reaction is reversible? - Answer-Because its a reaction that can go from reactants to products or products to reactants. What is chemical equilibrium? - Answer-When the rate of the forward reaction is equal to the rate of the reverse reaction. Why is water a polar molecule? - Answer-Because it has a partial negative charge and a partial positive charge because the oxygen is partially negatively charged and hydrogen is partially positive. What type of bonds do water molecules form with each other? - Answer-Hydrogen bonds What are the properties of water? - Answer-Cohesion, surface tension, high specific heat, heat of vaporization. Cohesion - Answer-high surface tension surface tension - Answer-measure of how hard it is to stretch/break the surface of a liquid high specific heat - Answer-the amount of energy it takes for temperature to raise 1 degreeHeat of Vaporization - Answer-amount of energy it takes to go from a liquid to a gas What is the density of water at various temperatures? - Answer-Water is frozen at 4 degrees celsius Why does ice float? - Answer-Because water molecules are more spread out when frozen (expand) How do hydrophilic and hydrophobic compounds interact with water? - Answer-Hydrophilic has high affinity for water ions (polar molecules), hydrophobic has low affinity for water ions (non polar molecules and non ionic elements) What is concentration? - Answer-how much solute is present per volume of solvent in moles What is solute? - Answer-substances that are dissolved What is a solvent? - Answer-the dissolving agent of a solution Why is water a good solvent? - Answer-Because it forms hydrogen bonds easily What types of solutes dissolve in water? - Answer-Hydrophilic solutes What pH range does an acidic solution have? - Answer-less than 7 What pH range does a basic solution have? - Answer-greater than 7 What pH range does a neutral solution have? - Answer-equal to 7 What does pH have to do with H+ concentration? - Answer-Acids have higher increase of H+, bases are any substances that reduce H+What is the formula used to calculate pH? - Answer-For each change in pH by one unit, H+ changes 10 fold. What is the pH of pure water? - Answer-7 How many H+ ions are in pure water - Answer-10^7-7M Buffers - Answer-stabilize substance that minimizes changes in H+ ions, OH- ion stabilizes. How does a base like KOH affect the H+ concentration in a solution - Answer-H+ bonds to the OHforming water, all thats left is K+ and water. Why is NH3 a base? - Answer-because is can react with a hydrogen ion What is an organic molecule? - Answer-consists of proteins, acids, DNA, fats and sugar What are the advantages of using carbon as a building block for organic molecules - Answer-carbon is tetravalent(can make 4 bonds), needs 4 electrons to fill valence shell, capable of making 4 chemical bonds, large complex and diverse molecules, accounts for the diversity of life on the planet