LECTURE PRESENTATIONS For CAMPBELL BIOLOGY NINTH EDITION Jane
LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 3 Water and Life Lectures by Erin Barley Kathleen Fitzpatrick
Overview: The Molecule That Supports All of Life • • • Water = biological medium on Earth Living things need water Most cells surrounded by water cells are about 70– 95% water Earth is habitable bc of abundance of water © 2011 Pearson Education, Inc.
Figure 3. 1
Concept 3. 1: Polar covalent bonds in water molecules result in hydrogen bonding • Water molecule is polar molecule: ends have opposite charges Polarity allows water molecules to form hydrogen bonds with each other https: //www. brainpop. com/science/earthsystem/water/ https: //youtu. be/c. Xefy. S 9 p 1 BE https: //youtu. be/PVL 24 HAesnc © 2011 Pearson Education, Inc.
Animation: Water Structure Right-click slide/select “Play” © 2011 Pearson Education, Inc.
Figure 3. 2 Hydrogen bond + + Polar covalent bonds + +
Figure 3. UN 01
Which one of the following hypothetical changes in a water molecule would tend to make it more polar? It is a linear molecule, as in H-O-H. Adjacent water molecules form covalent bonds with each other. The electronegativity values for H is increased. The electronegativity value for O is increased. All of the above would make water more polar.
Concept 3. 2: Four emergent properties of water contribute to Earth’s suitability for life • Four properties facilitate an environment for life: › › Cohesive behavior Ability to moderate temperature Expansion upon freezing Versatility as a solvent © 2011 Pearson Education, Inc.
The four emergent properties of water that are important for life are: a) b) c) d) e) Cohesion, expansion upon freezing, high heat of evaporation, and capillarity Cohesion, moderation of temperature, expansion upon freezing, and solvent properties Moderation of temperature, solvent properties, high surface tension, and capillarity Heat of vaporization, high specific heat, high surface tension, and capillarity Polarity, hydrogen bonding, high specific heat, and high surface tension
Cohesion of Water Molecules Hydrogen bonds hold water molecules together= cohesion Cohesion helps the transport of water against gravity in plants Adhesion = attraction between different substance Ex: between water and plant cell walls © 2011 Pearson Education, Inc.
Animation: Water Transport Right-click slide/select “Play” © 2011 Pearson Education, Inc.
Figure 3. 3 Adhesion Two types of water-conducting cells Cohesion Direction of water movement 300 m
Figure 3. 3 a Two types of water-conducting cells 300 m
Surface tension measures how hard it is to break the surface of a liquid Surface tension is related to cohesion © 2011 Pearson Education, Inc.
Figure 3. 4
Moderation of Temperature by Water absorbs heat from warmer air releases stored heat to cooler air © 2011 Pearson Education, Inc.
Heat and Temperature Kinetic energy = energy of motion • Heat = total amount of kinetic energy due to molecular motion • Temperature = intensity of heat due to average kinetic energy of molecules © 2011 Pearson Education, Inc.
Celsius scale A calorie (cal) =heat required to raise f 1 g of water 1°C Food “Calories” are kilocalories (kcal) kcal = 1, 000 cal Joule (J) = unit of energy 1 J = 0. 239 cal, or 1 cal = 4. 184 J © 2011 Pearson Education, Inc.
Water’s High Specific Heat Specific heat =amount of heat absorbed or lost for 1 g to change temperature 1ºC Water = 1 cal/g/ºC Water resists changing temperature bc of its high specific heat © 2011 Pearson Education, Inc.
Water’s high specific heat bc of hydrogen bonds › Heat absorbed when H bonds break › Heat released when H bonds form © 2011 Pearson Education, Inc.
High specific heat of water keeps temp changes moderate permits life
Figure 3. 5 Los Angeles (Airport) 75° 70 s (°F) 80 s 90 s 100 s San Bernardino 100° Riverside 96° Santa Ana Palm Springs 84° 106° Burbank 90° Santa Barbara 73° Pacific Ocean 68° San Diego 72° 40 miles
Evaporative Cooling Evaporation = liquid to gas Heat of vaporization = heat a liquid must absorb for 1 g to convert to gas Evaporation remaining surface cools= evaporative cooling Evaporative cooling stabilizes temps in organisms and bodies of water © 2011 Pearson Education, Inc.
Floating of Ice on Liquid Water Ice floats in liquid water bc hydrogen bonds in ice are more “ordered” ice less dense Water most dense at 4°C If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth © 2011 Pearson Education, Inc.
Figure 3. 6 Hydrogen bond Ice: Hydrogen bonds are stable Liquid water: Hydrogen bonds break and re-form
Figure 3. 6 a
Water: The Solvent of Life Solution = homogeneous mixture Solvent =dissolving agent of a solution Solute =substance that is dissolved Aqueous solution =water is the solvent © 2011 Pearson Education, Inc.
hydration shell- ions surrounded by water molecules © 2011 Pearson Education, Inc.
Figure 3. 7 Na Cl Na Cl
Water can also dissolve nonionic polar molecules Large polar molecules (ex. protein) can dissolve in water if ionic and polar regions © 2011 Pearson Education, Inc.
Figure 3. 8 +
Hydrophilic and Hydrophobic Substances A hydrophilic substance = has affinity for water A hydrophobic substance does not have affinity for water Oil molecules = hydrophobic bc mostly nonpolar bonds A colloid =stable suspension of small particles in a liquid © 2011 Pearson Education, Inc.
Solute Concentration in Aqueous Solutions Most biochemical reactions occur in water Chemical reactions depend on collisions of molecules [conc] of solutes is important © 2011 Pearson Education, Inc.
Molecular mass =sum of mass of atoms in molecule # molecules measured in moles(1 mole (mol) = 6. 02 x 1023 molecules) 6. 02 x 1023 daltons = 1 g Molarity (M) = # moles of solute per liter of solution © 2011 Pearson Education, Inc.
Possible Evolution of Life on Other Planets with Water Properties of water support life on Earth: Astrobiologists search for planets with water >200 planets found outside our solar system; one or two contain water In our solar system, Mars has water © 2011 Pearson Education, Inc.
Figure 3. 9
Concept 3. 3: Acidic and basic conditions affect living organisms A hydrogen atom 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 with the extra proton is now a hydronium ion (H 3 O+), though it is often represented as H+ › The molecule that lost the proton is now a hydroxide ion (OH–) © 2011 Pearson Education, Inc.
Water is in a state of dynamic equilibrium in which water molecules dissociate at the same rate at which they are being reformed © 2011 Pearson Education, Inc.
Figure 3. UN 02 + 2 H 2 O Hydronium ion (H 3 O+) Hydroxide ion (OH )
Though statistically rare, the dissociation of water molecules has a great effect on organisms Changes in concentrations of H+ and OH– can drastically affect the chemistry of a cell © 2011 Pearson Education, Inc.
Concentrations of H+ and OH– are equal in pure water Adding certain solutes, called acids and bases, modifies the concentrations of H+ and OH– Biologists use something called the p. H scale to describe whether a solution is acidic or basic (the opposite of acidic) © 2011 Pearson Education, Inc.
Acids and Bases An acid is any substance that increases the H+ concentration of a solution A base is any substance that reduces the H+ concentration of a solution © 2011 Pearson Education, Inc.
The p. H Scale • In any aqueous solution at 25°C the product of H+ and OH– is constant and can be written as [H+][OH–] = 10– 14 • The p. H of a solution is defined by the negative logarithm of H+ concentration, written as p. H = –log [H+] • For a neutral aqueous solution, [H+] is 10– 7, so p. H = –(– 7) = 7 © 2011 Pearson Education, Inc.
Acidic solutions have p. H values less than 7 Basic solutions have p. H values greater than 7 Most biological fluids have p. H values in the range of 6 to 8 © 2011 Pearson Education, Inc.
Figure 3. 10 H+ H+ + OH H H+ H+ Acidic solution Increasingly Acidic [H+] > [OH ] p. H Scale 0 1 Battery acid 2 Gastric juice, lemon juice 3 Vinegar, wine, cola 4 Tomato juice Beer Black coffee 5 6 OH H+ H+ OH OH + H+ H+ H Neutral solution OH OH H+ OH OH H+ OH Basic solution Neutral [H+] = [OH ] 7 8 Increasingly Basic [H+] < [OH ] OH Rainwater Urine Saliva Pure water Human blood, tears Seawater Inside of small intestine 9 10 Milk of magnesia 11 Household ammonia 12 13 14 Household bleach Oven cleaner
Figure 3. 10 a
Figure 3. 10 b
Figure 3. 10 c
Figure 3. 10 d
Buffers The internal p. H of most living cells must remain close to p. H 7 Buffers are substances that minimize changes in concentrations of H+ and OH– in a solution Most buffers consist of an acid-base pair that reversibly combines with H+ http: //www. mhhe. com/physsci/chemistry/essentialchemistry/flash/buffer 12. swfhttp: //w ww. chemistry. uoguelph. ca/educmat/chm 19104/chemtoons 7. htm © 2011 Pearson Education, Inc.
Acidification: A Threat to Water Quality Human activities such as burning fossil fuels threaten water quality CO 2 is the main product of fossil fuel combustion About 25% of human-generated CO 2 is absorbed by the oceans CO 2 dissolved in sea water forms carbonic acid; this process is called ocean acidification © 2011 Pearson Education, Inc.
Figure 3. 11 CO 2 + H 2 O H 2 CO 3 H+ + HCO 3 H+ + CO 32 + Ca 2+ HCO 3 Ca. CO 3
As seawater acidifies, H+ ions combine with carbonate ions to produce bicarbonate Carbonate is required for calcification (production of calcium carbonate) by many marine organisms, including reef-building corals © 2011 Pearson Education, Inc.
Figure 3. 12 (a) (b) (c)
Figure 3. 12 a (a)
Figure 3. 12 b (b)
Figure 3. 12 c (c)
The burning of fossil fuels is also a major source of sulfur oxides and nitrogen oxides These compounds react with water in the air to form strong acids that fall in rain or snow Acid precipitation is rain, fog, or snow with a p. H lower than 5. 2 Acid precipitation damages life in lakes and streams and changes soil chemistry on land © 2011 Pearson Education, Inc.
Figure 3. UN 03
Figure 3. UN 04 Ice: stable hydrogen bonds Liquid water: transient hydrogen bonds
Figure 3. UN 05 0 Acidic [H+] > [OH ] Neutral [H+] = [OH ] Basic [H+] < [OH ] Acids donate H+ in aqueous solutions. 7 Bases donate OH or accept H+ in aqueous solutions 14
Calcification rate (mmol Ca. CO 3/m 2 • day) Figure 3. UN 06 40 200 250 [CO 32 ] ( mol/kg)
Figure 3. UN 07
Figure 3. UN 08
Figure 3. UN 09
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