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Chapter 2 of Principles of Biology

by: mscrowell

Chapter 2 of Principles of Biology Bio 112

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About this Document

Chapter 2 covered Matter and chemical reactions. Includes visuals.
principles of biology
Dr. Hannah Henson
Class Notes




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This 10 page Class Notes was uploaded by mscrowell on Sunday August 28, 2016. The Class Notes belongs to Bio 112 at Union University taught by Dr. Hannah Henson in Fall 2016. Since its upload, it has received 5 views. For similar materials see principles of biology in Biology at Union University.


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Date Created: 08/28/16
2.1 What is Matter?  o Matter is anything that takes up space and has mass   It is composed of: o Elements: substance that can’t be broken down into another substance o Compounds: two or more different elements      2.2 What do an element’s properties depend upon?  o The structure of its atoms: the smallest unit of matter that still retains  properties of an element o Atoms are composed of?  Subatomic particles: neutrons, protons, electrons   Isotopes: different number of neutrons   o Two atoms of an element that differ in number of neutrons o Radioactive isotopes decay spontaneously, giving off particles and  energy  E.g. Carbon­14 dating PET Scans (Positron Emission Tomography)  o Isotopic labeling: tracks the passage of an isotope through a reaction,  metabolic pathway, or cell.  o 18F: fluorodeoxyglucose      Cancer cells utilize glucose and can be seen on a PET scan as a highlighted  area    Electrons contain energy   o What is energy?  Energy is the ability to do work o Potential energy: depends on location or structure o Electrons differ in potential energy Work is needed to move electrons away from protons Lost energy released into environment as heat   Valence electrons determine chemical behavior    2.3: Chemical bonds between atoms determine formation and function of molecules o Chemical bonds: share or transfer of valence electrons  A  charged atom is an ion  o Cation o Anion o Ionic bonds: attraction of two ions of opposite charge   Van Der Waals Interactions:  the residual attractive or repulsive forces  between molecules or atomic groups that do not arise from a covalent bond, or  ionic bonds.   o Biological molecules recognize and interact with each other with a  specificity based on molecular shape o Molecules with similar shapes can have similar biological effects   2.4 Chemical Reactions: Making or breaking chemical  bonds   o Structure determines function o All chemical reactions are reversible: products of the forward reaction  become reactants for the reverse reaction o Chemical equilibrium is reached when the forward and reverse reaction rates are equal    2.5: Hydrogen bonding gives water properties that help  make life possible on Earth  o All organisms are made mostly of water and live in an environment  dominated by water o Water molecules are polar molecules, with the oxygen region having a  partial negative charge (δ−) and the hydrogen region a slight positive  charge (δ+) o Two water molecules are held together by a hydrogen bond     Four emergent properties of water contribute to Earth’s suitability for life:  Cohesive behavior  Ability to moderate temperature  Expansion upon freezing  Versatility as a solvent o Cohesion of Water Molecules o Water molecules are linked by multiple hydrogen bonds  The molecules stay close together because of this; it is called  cohesion o Cohesion due to hydrogen bonding contributes to the transport of water  and nutrients against gravity in plants  Adhesion, the clinging of one substance to another, also plays a  role o Surface tension is a measure of how hard it is to break the surface of a  liquid o Surface tension is related to cohesion  Moderation of Temperature by Water   o Water absorbs heat from warmer air and releases stored heat to cooler  air o Water can absorb or release a large amount of heat with only a slight  change in its own temperature  Temperature and Heat  o Kinetic energy is the energy of motion o Thermal energy is a measure of the total amount of kinetic energy due  to molecular motion o Temperature represents the average kinetic energy of molecules o Thermal energy in transfer from one body of matter to another is defined as heat   o A calorie (cal) is the amount of heat required to raise the temperature of  1 g of water by 1°C o The “calories” on food packages are actually kilocalories (kcal), where  1 kcal = 1,000 cal o The joule (J) is another unit of energy, where 1 J = 0.239 cal, or 1 cal =  4.184 J o Ice floats in liquid water because hydrogen bonds in ice are more “ordered,” making ice less dense o Water reaches its greatest density at 4°C o If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth Water: The Solvent of Life o A solution is a liquid that is a homogeneous mixture of substances o A solvent is the dissolving agent of a solution o The solute is the substance that is dissolved o An aqueous solution is one in which water is the solvent Hydrophilic and Hydrophobic Substances o A hydrophilic substance is one that has an affinity for water o A hydrophobic substance is one that does not have an affinity for water o Oil molecules are hydrophobic because they have relatively nonpolar  covalent bonds     o Molecular mass is the sum of all masses of all atoms in a molecule o Numbers of molecules are usually measured in moles, where 1 mole  23  (mol) = 6.02 × 10 molecules o Avogadro’s number and the unit dalton were defined such that 6.02 ×  23 10  daltons = 1 g o Molarity (M) is the number of moles of solute per liter of solution  Acids and Bases   + o Sometimes a hydrogen ion (H ) is transferred from one water molecule to another, leaving behind a hydroxide − ion (OH ) o The proton (H ) binds to the other water molecule, forming a hydronium ion (H O ) + + 3 o By convention, H is used to represent the hydronium ion      + −  In any aqueous solution at 25°C, the product of H  and OH is constant and can be  written as o [H ][OH ] = 10 −14 + The pH of a solution is defined as the negative logarithm of H  concentration,  written as + o pH = −log [H ] For a neutral aqueous solution, [H ] is 10 M, so + o −log [H ]  = −(−7) = 7    Buffers   o The internal pH of most living cells must remain close to pH 7 + o Buffers are substances that minimize changes in concentrations of H   and OH  in a solution  Most buffer solutions contain a weak acid and its corresponding  base, which combine reversibly with H +   


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