chapter3_Water-and-the-Fitness-of-the-Envt.pdf

Chapter 3 Water and the Fitness of the Environment PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Overview: The Molecule That Supports All of Life...

Chapter 3 Water and the Fitness of the Environment PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Overview: The Molecule That Supports All of Life – Water is the biological medium here on Earth – All living organisms require water more than any other substance Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Three-quarters of the Earth’s surface is submerged in water The abundance of water is the main reason the Earth is habitable Figure 3.1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Concept 3.1: The polarity of water molecules results in hydrogen bonding The water molecule is a polar molecule Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The polarity of water molecules – Allows them to form hydrogen bonds with each other – Contributes to the various properties water exhibits – + Hydrogen H bonds + – H – + + – Figure 3.2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Concept 3.2: Four emergent properties of water contribute to Earth’s fitness for life Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cohesion Water molecules exhibit cohesion Cohesion – Is the bonding of a high percentage of the molecules to neighboring molecules – Is due to hydrogen bonding Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cohesion – Helps pull water up through the microscopic vessels of plants Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Surface tension – Is a measure of how hard it is to break the surface of a liquid – Is related to cohesion Figure 3.4 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Moderation of Temperature Water moderates air temperature – By absorbing heat from air that is warmer and releasing the stored heat to air that is cooler Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Heat and Temperature Kinetic energy – Is the energy of motion Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Heat – Is a measure of the total amount of kinetic energy due to molecular motion Temperature – Measures the intensity of heat Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Water’s High Specific Heat The specific heat of a substance – Is the amount of heat that must be absorbed or lost for 1 gram of that substance to change its temperature by 1ºC Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Water has a high specific heat, which allows it to minimize temperature fluctuations to within limits that permit life – Heat is absorbed when hydrogen bonds break – Heat is released when hydrogen bonds form Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Evaporative Cooling Evaporation – Is the transformation of a substance from a liquid to a gas Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Heat of vaporization – Is the quantity of heat a liquid must absorb for 1 gram of it to be converted from a liquid to a gas Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Evaporative cooling – Is due to water’s high heat of vaporization – Allows water to cool a surface Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Insulation of Bodies of Water by Floating Ice Solid water, or ice – Is less dense than liquid water – Floats in liquid water Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The hydrogen bonds in ice – Are more “ordered” than in liquid water, making ice less dense Hydrogen bond Ice Liquid water Figure 3.5 Hydrogen bonds are stable Hydrogen bonds constantly break and re-form Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Since ice floats in water – Life can exist under the frozen surfaces of lakes and polar seas Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The Solvent of Life Water is a versatile solvent due to its polarity It can form aqueous solutions Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The different regions of the polar water molecule can interact with ionic compounds called solutes and dissolve them Negative oxygen regions – of polar water molecules Na+ are attracted to sodium + – + cations (Na+). + – – Positive hydrogen regions Na+ – of water molecules + + cling to chloride anions Cl– Cl – (Cl–). – + – + – + – – Figure 3.6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Water can also interact with polar molecules such as proteins This oxygen is attracted to a slight – positive charge on the lysozyme + molecule. This oxygen is attracted to a slight negative charge on the lysozyme molecule. (a) Lysozyme molecule (b) Lysozyme molecule (purple) (c) Ionic and polar regions on the protein’s in a nonaqueous in an aqueous environment Surface attract water molecules. Figure 3.7 environment such as tears or saliva Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Hydrophilic and Hydrophobic Substances A hydrophilic substance – Has an affinity for water Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  A hydrophobic substance – Does not have an affinity for water Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Solute Concentration in Aqueous Solutions Since most biochemical reactions occur in water – It is important to learn to calculate the concentration of solutes in an aqueous solution Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  A mole – Represents an exact number of molecules of a substance in a given mass Molarity – Is the number of moles of solute per liter of solution Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Concept 3.3: Dissociation of water molecules leads to acidic and basic conditions that affect living organisms Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Water can dissociate – Into hydronium ions and hydroxide ions Changes in the concentration of these ions – Can have a great affect on living organisms + – H H H H + Figure on p. 53 of water H H H H dissociating Hydronium Hydroxide ion (H3O+) ion (OH–) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Effects of Changes in pH Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Acids and Bases An acid – Is any substance that increases the hydrogen ion concentration of a solution A base – Is any substance that reduces the hydrogen ion concentration of a solution Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The pH Scale The pH of a solution -p H means “power of hydrogen” – Is determined by the relative concentration of hydrogen ions – Is low in an acid – Is high in a base Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The pH scale and pH values of various aqueous solutions Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Buffers The internal pH of most living cells – Must remain close to pH 7 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Buffers – Are substances that minimize changes in the concentrations of hydrogen and hydroxide ions in a solution – Consist of an acid-base pair that reversibly combines with hydrogen ions Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The Threat of Acid Precipitation Acid precipitation – Refers to rain, snow, or fog with a pH lower than pH 5.6 – Is caused primarily by the mixing of different pollutants with water in the air Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Acid precipitation – Can damage life in Earth’s ecosystems 0 More 1 acidic 2 3 Acid 4 rain 5 Normal 6 rain 7 8 9 10 11 12 13 More 14 basic Figure 3.9 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings