Ch 3: Water and Life Water and Life Essential Knowledge: 2.A.3 Organisms must exchange matter with the environment to grow, reproduce, and maintain organization Water and Life Okladek 2015

Why are we studying water? Okladek 2015

Bonds in Biology Weak bonds Strong bonds _______________________ H2O Weak bonds _______________________ attraction between + and – _______________________interactions interactions with H2O van derWaals forces ionic Strong bonds __________________ sharing electrons H2O – H2 (hydrogen gas) Okladek 2015

Chemistry of water H2O molecules form H-bonds with each other __________ attracted to ___________ creates a sticky molecule APBio/TOPICS/Biochemistry/Movies AP/hydrogenbonds-Thinkwell.swf Okladek 2015

Figure 3.2    +    +    +    + Figure 3.2 Hydrogen bonds between water molecules. Okladek 2015 5

Special properties of water 1. _____________________________ surface tension, capillary action 2. _____________________________ many molecules dissolve in H2O hydrophilic vs. hydrophobic 3. _____________________________ ice floats! 4. _____________________________ water stores heat 5. ______________________________ heats & cools slowly Okladek 2015

1. Cohesion & Adhesion Cohesion Adhesion H bonding between H2O molecules water is “sticky” _________________________________ drinking straw Adhesion H bonding between H2O & other substances _____________________ water climbs up paper towel or cloth Cohesion H bonding between H2O molecules water is “sticky” surface tension capillary action drinking straw Adhesion H bonding between H2O & other substances meniscus water climbs up paper towel or cloth Okladek 2015

Surface Tension Surface tension is a measure of ______________ _____________________________________ Surface tension is related to ________________ Cohesion H bonding between H2O molecules water is “sticky” surface tension capillary action drinking straw Adhesion H bonding between H2O & other substances meniscus water climbs up paper towel or cloth Okladek 2015

How does H2O get to top of trees? APBio/TOPICS/04Biochemistry/MoviesAP/03_03WaterTransport_A.swf Okladek 2015

2. Water is the solvent of life (universal solvent) Polarity makes H2O a good solvent polar H2O molecules surround + & – ions solvents dissolve ____________ creating ______________ 2. Water is a good solvent = the solvent of life Polarity makes H2O a good solvent polar H2O molecules surround + & – ions solvents dissolve solutes creating solutions What dissolves in water easily? polar or non-polar molecules? How about oxygen -- does that dissolve in H2O? Okladek 2015

What dissolves in water? ____________________________ substances have attraction to H2O polar or non-polar? Hydrophilic substances have attraction to H2O Okladek 2015

What doesn’t dissolve in water? ________________________ substances that don’t have an attraction to H2O polar or non-polar? Oh, look hydrocarbons! Hydrophobic substances that don’t have an attraction to H2O fat (triglycerol) Okladek 2015

3. The special case of ice Most (all?) substances are more dense when they are solid, but not water… __________________ H bonds form a crystal Most (all?) substances are more dense when they are solid, but not water… Lower density as a solid = Ice floats! H bonds form a crystal Okladek 2015

Why is “ice floats” important? Oceans & lakes don’t freeze solid ___________________________________ allowing life to survive the winter if ice sank… ponds, lakes & even oceans would freeze solid in summer, only upper few inches would thaw seasonal turnover of lakes ________________________________________ Oceans & lakes don’t freeze solid surface ice insulates water below allowing life to survive the winter if ice sank… ponds, lakes & even oceans would freeze solid in summer, only upper few inches would thaw seasonal turnover of lakes sinking cold H2O cycles nutrients in autumn Okladek 2015

4. Water’s High Specific Heat The specific heat of a substance is the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1ºC The specific heat of water is 1 cal/g/ºC Water resists changing its temperature because of its high specific heat Water’s high specific heat can be traced to hydrogen bonding Heat is _________________ when hydrogen bonds break Heat is __________________ when hydrogen bonds form Okladek 2015

Specific heat ____________________________________ high specific heat takes a lot to heat it up takes a lot to cool it down _______________________________ (The high specific heat of water minimizes temperature fluctuations to within limits that permit life) Specific heat H2O resists changes in temperature high specific heat = heats & cools slowly takes a lot to heat it up takes a lot to cool it down H2O moderates temperatures on Earth Okladek 2015

FYI… Heat and Temperature _________________is the energy of motion __________ is a measure of the total amount of kinetic energy due to molecular motion _______________measures the intensity of heat due to the average kinetic energy of molecules Okladek 2015

The Celsius scale is a measure of temperature using Celsius degrees (°C) A ___________is the amount of heat required to raise the temperature of 1 g of water by 1°C The “calories” on food packages are actually ________________, where 1 kcal = 1,000 cal The _____________is another unit of energy where 1 J = 0.239 cal, or 1 cal = 4.184 J Okladek 2015

5. Evaporative Cooling Evaporation is transformation of a substance from liquid to gas ________________is the heat a liquid must absorb for 1 g to be converted to gas As a liquid evaporates, its remaining surface cools, a process called ________________________ Evaporative cooling of water helps stabilize temperatures in organisms and bodies of water Okladek 2015

Heat of vaporization Okladek 2015

6. Ionization of water & pH Water ionizes H+ splits off from H2O, leaving OH– if [H+] = [-OH], water is if [H+] > [-OH], water is if [H+] < [-OH], water is ________________________ how acid or basic solution is 1  7  14 Water ionizes H+ splits off from H2O, leaving OH– H2O  H+ + OH– if [H+] = [-OH], water is neutral if [H+] > [-OH], water is acidic if [H+] < [-OH], water is basic pH scale how acid or basic solution is 1  7  14 H2O  H+ + OH– Okladek 2015

tenfold change in H+ ions ____________________ pH Scale 10–1 H+ Ion Concentration Examples of Solutions Stomach acid, Lemon juice 1 pH 100 Hydrochloric acid 10–2 2 10–3 Vinegar, cola, beer 3 10–4 Tomatoes 4 10–5 Black coffee, Rainwater 5 10–6 Urine, Saliva 6 10–7 Pure water, Blood 7 10–8 Seawater 8 10–9 Baking soda 9 10–10 Great Salt Lake 10 10–11 Household ammonia 11 10–12 Household bleach 12 10–13 Oven cleaner 13 10–14 Sodium hydroxide 14 tenfold change in H+ ions pH1  pH2 10-1  10-2 ___________________ pH8  pH7 10-8  10-7 ____________________ pH10  pH8 10-10  10-8 In pure water only 1 water molecule in every 554 million is dissociated tenfold change in H+ ions pH1  pH2 10-1  10-2 10 times less H+ pH8  pH7 10-8  10-7 10 times more H+ pH10  pH8 10-10  10-8 100 times more H+ Okladek 2015

Buffers & cellular regulation pH of cells must be kept ~7 ____________________________________ Control pH by _________ reservoir of H+ donate H+ when [H+] falls absorb H+ when [H+] rises 1 2 3 4 5 6 7 8 9 Amount of base added Buffering range pH Exercise = acidic in muscles CO2 = carbonic acid lactic acid body uses buffers to counter act this Okladek 2015