Campbell Biology Chapter 3: Water and Life - 3rd Canadian Edition PDF

Campbell Biology Third Canadian Edition Chapter 3 Water and Life Copyright © 2021 Pearson Canada, Inc. 3-1 Key Concepts Polar covalent bonds in water molecules result in hydrogen bonding Four emergent properties of water contribute to Earth’s suitability for life Acidic and basic conditions affect l...

Campbell Biology Third Canadian Edition Chapter 3 Water and Life Copyright © 2021 Pearson Canada, Inc. 3-1 Key Concepts Polar covalent bonds in water molecules result in hydrogen bonding Four emergent properties of water contribute to Earth’s suitability for life Acidic and basic conditions affect living organisms Copyright © 2021 Pearson Canada, Inc. 3-2 Overview: The Molecule That Supports All of Life (1 of 2) Water is the biological medium on Earth All living organisms require water Due to climate change ratio of liquid water to ice is changing affecting the lives of organisms living in the Arctic Figure 3.1 How does the life on Earth depend on the chemistry of water? Copyright © 2021 Pearson Canada, Inc. 3-3 Overview: The Molecule That Supports All of Life (2 of 2) Water is the only common substance to exist in the natural environment in all three physical states Most cells are surrounded by water, and are 70–95% water Abundance of water is an important reason Earth is habitable Copyright © 2021 Pearson Canada, Inc. 3-4 Concept 3.1: Polar covalent bonds in water result in hydrogen bonding Water is a polar molecule due to highly electronegative oxygen atom – the overall charge is unevenly distributed Polarity allows water molecules to form hydrogen bonds with each other Figure 3.2 Hydrogen bonds between water molecules. Copyright © 2021 Pearson Canada, Inc. 3-5 Concept 3.2: Four emergent properties of water contribute to Earth’s suitability for life Four of water’s properties that facilitate an environment that is for life are: – Cohesive behaviour – Ability to moderate temperature – Expansion upon freezing – Versatility as a solvent Copyright © 2021 Pearson Canada, Inc. 3-6 Cohesion of Water Molecules (1 of 4) Hydrogen bonds hold water Figure 3.3 Water transport in molecules together, a plants. phenomenon called cohesion Cohesion helps the transport of water against gravity in plants Copyright © 2021 Pearson Canada, Inc. 3-7 Cohesion of Water Molecules (2 of 4) Animation: Water Transport Right-click slide/select “Play” Copyright © 2021 Pearson Canada, Inc. 3-8 Cohesion of Water Molecules (3 of 4) Adhesion is an attraction between different substances – for example, between water and plant cell walls Figure 3.3a Water transport in plants. Copyright © 2021 Pearson Canada, Inc. 3-9 Cohesion of Water Molecules (4 of 4) Surface tension is a measure of how hard it is to break the surface of a liquid Water has an unusually high surface tension due to hydrogen bonding between the molecules at the air-water interface and to the water molecules below Figure 3.4 Walking on water. Copyright © 2021 Pearson Canada, Inc. 3 - 10 Moderation of Temperature by Water Water absorbs heat from warmer air and releases stored heat to cooler air Water absorbs or releases a large amount of heat with little change in its own temperature Figure 3.5 Temperature for the Pacific Ocean and Southern California on an August day. Copyright © 2021 Pearson Canada, Inc. 3 - 11 Temperature and Heat (1 of 2) Kinetic energy is the energy of motion – The kinetic energy associated with random motion of atoms or molecules is called thermal motion Temperature is a measure of energy that represents the average kinetic energy of molecules Thermal energy in transfer from one body of matter to another is defined as heat Copyright © 2021 Pearson Canada, Inc. 3 - 12 Temperature and Heat (2 of 2) Celsius scale is a measure of temperature in Celsius degrees (°C) A calorie (cal) is the amount of heat required to raise the temperature of 1 g water by 1°C “Calories” listed on food packages are actually kilocalories (kcal): – 1 kcal = 1,000 cal The joule (J) is another unit of energy – 1 J = 0.239 cal, or 1 cal = 4.184 J Copyright © 2021 Pearson Canada, Inc. 3 - 13 Water’s High Specific Heat (1 of 2) Specific heat is the amount of heat that must be absorbed or lost for 1 g of a substance to change temperature by 1ºC The specific heat of water is 1 cal/g/ºC Water resists changing its temperature because of its high specific heat Copyright © 2021 Pearson Canada, Inc. 3 - 14 Water’s High Specific Heat (2 of 2) Water’s high specific heat is due to hydrogen bonding – Heat absorbed when hydrogen bonds break – Heat released when hydrogen bonds form Water’s high specific heat minimizes temperature fluctuations to within limits that permit life Copyright © 2021 Pearson Canada, Inc. 3 - 15 Evaporative Cooling Evaporation- transformation of a substance from liquid to gas Heat of vaporization is the heat a liquid must absorb for 1 g to be converted to gas Water has a high heat of vaporization than most other liquids Evaporative cooling- as a liquid evaporates its remaining surface cools Evaporative cooling of water stabilizes temperatures of organisms and bodies of water Copyright © 2021 Pearson Canada, Inc. 3 - 16 Water and Life (1 of 4) THINK-PAIR-SHARE Why do you think you feel warmer and more uncomfortable at 37C at 100% humidity vs at 37C and 30% humidity? Copyright © 2021 Pearson Canada, Inc. 3 - 17 Floating of Ice on Liquid Water Ice floats in liquid water because hydrogen bonds in ice are more “ordered,” making ice less dense Figure 3.6 Ice: crystalline structure and floating barrier. Copyright © 2021 Pearson Canada, Inc. 3 - 18 Water and Life (2 of 4) THINK-PAIR-SHARE What would be the effect on the freezing temperature of adding salt to water? Copyright © 2021 Pearson Canada, Inc. 3 - 19 Floating of Ice on Liquid Water (1 of 2) Water reaches its greatest density at 4°C If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth Copyright © 2021 Pearson Canada, Inc. 3 - 20 Floating of Ice on Liquid Water (2 of 2) Many scientists are worried that global warming, caused by carbon dioxide and other greenhouse gases, is having a profound effect on icy environments around the globe The rate at which glaciers and Arctic sea ice are disappearing is posing an extreme challenge to animals that depend on ice for their survival Copyright © 2021 Pearson Canada, Inc. 3 - 21 Figure 3.7 Effects of Climate Change on the Arctic Copyright © 2021 Pearson Canada, Inc. 3 - 22 Water: The Solvent of Life (1 of 3) A Solution is a liquid that is a homogeneous mixture of substances A Solvent is the dissolving agent of a solution The Solute is the substance that is dissolved An Aqueous solution is one in which water is the solvent Copyright © 2021 Pearson Canada, Inc. 3 - 23 Water: The Solvent of Life (2 of 3) Water is a versatile solvent due to its polarity – forms hydrogen bonds readily When an ionic compound is dissolved in water, each ion is surrounded by water molecules (hydration shell) Figure 3.8 Table salt dissolving in water. Copyright © 2021 Pearson Canada, Inc. 3 - 24 Water: The Solvent of Life (3 of 3) Water can also dissolve nonionic polar molecules or compounds Large polar molecules such as proteins can dissolve in water if they have polar or ionic regions Figure 3.9 A water-soluble protein. Copyright © 2021 Pearson Canada, Inc. 3 - 25 Hydrophilic and Hydrophobic Substances Hydrophilic substance has an affinity for water Hydrophobic substance does not have an affinity for water Oil molecules are hydrophobic because they have relatively nonpolar bonds Hydrophobic molecules related to oils are the major components of cell membranes Copyright © 2021 Pearson Canada, Inc. 3 - 26 Solute Concentration in Aqueous Solutions (1 of 2) Most biochemical reactions occur in water – Chemical reactions depend on collisions of molecules and therefore on solute concentration When carrying out experiments, we use mass to calculate the number of solute molecules in a solution Copyright © 2021 Pearson Canada, Inc. 3 - 27 Solute Concentration in Aqueous Solutions (2 of 2) Molecular mass- sum of mass of all the atoms in a molecule Numbers of molecules are usually measured in moles 1 mole (mol) = 6.02 × 1023 molecules Avogadro’s number and daltons were defined as 6.02 × 1023 daltons = 1 g Molarity (M)- number of moles of solute per litre of solution Copyright © 2021 Pearson Canada, Inc. 3 - 28 Water and Life (3 of 4) THINK-PAIR-SHARE Example molecular mass of sucrose Molecular formula C12H22011 Mass of C is 12 daltons, H is 1 dalton and 0 is 16 Molecular mass of sucrose is (12×12) + (22×1) + (11×16) = 342 daltons You would need 342 grams of sucrose to make 1mol solution Calculate number g to make 1mol of NaCl Copyright © 2021 Pearson Canada, Inc. 3 - 29 Possible Evolution of Life on Other Planets with Water (1 of 2) Water supports life on Earth in many ways Astrobiologists seeking life on other planets concentrate their search on planets with water Copyright © 2021 Pearson Canada, Inc. 3 - 30 Possible Evolution of Life on Other Planets with Water (2 of 2) Out of the 800 planets found outside our solar system, only one or two of them contain water In our solar system, Mars has been found to have water Figure 3.10 Evidence for liquid water on Mars. Copyright © 2021 Pearson Canada, Inc. 3 - 31 Concept 3.3: Acidic and basic conditions affect living organisms A hydrogen atom participating in a hydrogen bond between two water molecules can shift from one to the other – The hydrogen atom leaves its electron behind and is transferred as a proton, or hydrogen ion (H+) – The molecule that lost the proton is now a hydroxide ion (OH−) – The molecule with the extra proton is now a hydronium ion (H3O+), though it is often represented as H+ Copyright © 2021 Pearson Canada, Inc. 3 - 32 Acidic and basic conditions affect living organisms (1 of 2) Water is in a state of dynamic equilibrium – water molecules dissociate at same rate they are being reformed Copyright © 2021 Pearson Canada, Inc. 3 - 33 Acidic and basic conditions affect living organisms (2 of 2) The dissociation of water molecules is rare, but has a great effect on organisms Changes in concentrations of H+ and OH− can affect cell chemistry Concentrations of H+ and OH− are equal in pure water Adding acids and bases, modifies concentrations of H+ and OH− The pH scale is used to describe whether a solution is acidic or basic Copyright © 2021 Pearson Canada, Inc. 3 - 34 Acids and Bases Acid- any substance that increases the H+ concentration of a solution Base – any substance that reduces the H+ concentration of a solution Alrhough strong acids and bases dissociate completly in water, weak acids Weak acids are acids and bases reversibly release and accept back hydrogen ions. Copyright © 2021 Pearson Canada, Inc. 3 - 35 The pH Scale (1 of 2) In any aqueous solution at 25°C product of H+ and OH− is constant and written as [H+][OH−] = 10−14 The pH of a solution is defined by negative logarithm of H+ concentration, written as pH = −log [H+] For a neutral aqueous solution, [H+] is 10−7, so pH = −(−7) = 7 Copyright © 2021 Pearson Canada, Inc. 3 - 36 The pH Scale (2 of 2) Acidic solutions have pH values less than 7 Figure 3.11 The pH scale and pH values of some aqueous solutions. Basic solutions have pH values greater than 7 Most biological fluids have pH values in the range of 6 to 8 Copyright © 2021 Pearson Canada, Inc. 3 - 37 Water and Life (4 of 4) THINK-PAIR-SHARE What do you think the purpose of having your stomach at pH 2? Copyright © 2021 Pearson Canada, Inc. 3 - 38 Buffers The internal pH of most living cells must remain close to pH 7 Buffers minimize changes in concentrations of H+ and OH− in a solution – Buffers contain a weak acid and corresponding base, which combine reversibly with H+ ions Copyright © 2021 Pearson Canada, Inc. 3 - 39 Acidification: A Threat to Water Quality (1 of 2) Human activities such as burning fossil fuels threaten water quality CO2 is the main product of fossil fuel combustion About 25% of human-generated CO2 is absorbed by the oceans CO2 dissolved in sea water forms carbonic acid – Process called ocean acidification Copyright © 2021 Pearson Canada, Inc. 3 - 40 Acidification: A Threat to Water Quality (2 of 2) As seawater acidifies, H+ ions Figure 3.12 Atmospheric CO2 from combine with carbonate ions to human activities and its fate in the ocean. produce bicarbonate Carbonate is required for calcification (production of calcium carbonate) by many marine organisms, such as corals Progress has been made in learning about the delicate chemical balances in oceans, lakes and rivers Copyright © 2021 Pearson Canada, Inc. 3 - 41 IMPACT: The Threat of Ocean Acidification to Marine life Ocean acidification is threatening coral reefs, which are rich in biodiversity, protect shorelines, and provide important ecosystems for many marine organisms Figure 3.13 Impact The Threat of Ocean Acidification to Marine Life Copyright © 2021 Pearson Canada, Inc. 3 - 42