biol 101 chp 3: water and life
DESCRIPTION
This is a lecture presentation for my BIOL 101 General Biology I students on Chapter 3: Water and Life. (Campbell Biology, 10th Ed. by Reece et al). Rob Swatski, Associate Professor of Biology, Harrisburg Area Community College - York Campus, York, PA. Email: [email protected] Please visit my website for more anatomy and biology learning resources: http://robswatski.virb.com/TRANSCRIPT
BIOL 101 General Biology I
Chapter 3
Water & the Fitness of the Environment
Rob Swatski Associate Professor of Biology
HACC – York Campus 1
2
Water: The Molecule That Supports All of Life
• Water is the biological medium on Earth
• All living organisms require water more than any other substance
• Most cells are surrounded by water, and cells themselves are about 70–95% water
• The abundance of water is the main reason the Earth is habitable
3
Water = Life
4
Surface of Mars Surface of Earth
5
Water = Polar molecule
N
S
+
-
6
–
H
+
H
O
+
+
+
–
–
– Hydrogen bond
7
Properties of Water
How do they benefit living things? 8
Emergent Properties of Water
Cohesion Moderates
temperature Expands
when frozen Versatile solvent
9
10
Cohesion
How?
Water-conducting cells
Adhesion
Cohesion
150 µm
Direction of water movement
11
12
Surface Tension
How?
13
14
Moderates Temperature
15
Moderation of Temperature by Water
• Water absorbs heat from warmer air and releases stored heat to cooler air
• Water can absorb or release a large amount of heat with only a slight change in its own temperature
16
17
Energy & Water
Potential
Kinetic
Heat
Temperature
Metric System Units - Energy
Celsius calorie
(cal)
kilocalorie (kcal or Calorie)
joule
1j = 0.239 cal
1 cal = 4.184 j
18
Specific Heat
1 cal/g/ºC
So what…?
HEAT +/- 1 g 1ºC
19
• Water’s high specific heat can be traced to hydrogen bonding
– Heat is absorbed when hydrogen bonds break
– Heat is released when hydrogen bonds form
• The high specific heat of water minimizes temperature fluctuations to within limits that permit life
20
–
H
+
H
O
+
+
+
–
–
– Hydrogen bond
21
22
Heat Heat
What happens to the bond?
23
24
Heat Heat
What happens to the bond?
Santa Barbara 73°
Los Angeles
(Airport) 75°
Pacific Ocean 68°
Santa Ana 84°
Burbank 90°
San Bernardino 100°
Palm Springs 106°
Riverside 96°
San Diego 72° 40 miles
70s (°F)
80s
90s
100s
25
26
27
28
Evaporation
Heat of evaporation
Evaporative cooling
Helps stabilize
temperatures
29
Floating of Ice on Liquid Water
• Ice floats in liquid water because hydrogen bonds in ice are more “ordered,” making ice less dense
• Water reaches its greatest density at 4°C
• If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth
30
Ice and Insulation
31
32
Solute Solvent Solution
Aqueous solution
Hydration shell
33
“Like Dissolves Like”
34
35
Polar Polar
Hydrophilic
36
Polar Nonpolar
Hydrophobic
Colloid
37
Solute Concentration in Aqueous Solutions
• Most biochemical reactions occur in water
• Chemical reactions depend on collisions of molecules and therefore on the concentration of solutes in an aqueous solution
38
• Molecular mass: the sum of all masses of all atoms in a molecule
• Numbers of molecules are usually measured in moles, where 1 mole (mol) = 6.02 x 1023 molecules
• Avogadro’s number and the unit dalton were defined such that 6.02 x 1023 daltons = 1 g
• Molarity (M): the number of moles of solute per liter of solution
39
40
One Mole =
molecules
41
42
Hydronium ion (H3O+)
Hydroxide ion (OH–)
2H2O
H
H
H
H
H
H
H
H
O O O O
Hydrogen is Shifty
gains H+ loses H, but keeps e-
43
Dynamic equilibrium: dissociation rate = reformation rate
44 anions cations both
45
pH Scale
Acidic [H+] > [OH–]
Neutral [H+] = [OH–]
Basic [H+] < [OH–]
7
0
14
46
pH Scale
Battery acid
Gastric juice, lemon juice
Vinegar, wine,
cola
Beer Tomato juice
Black coffee
Rainwater
Urine
Saliva
Pure water
Human blood, tears
Seawater
Inside of small intestine
Milk of magnesia
Household ammonia
Household
bleach
Oven cleaner
Basic solution
Neutral solution
Acidic solution
0
1
2
3
4
5
6
7
8
9
10
Neutral
[H+] = [OH]
Inc
rea
sin
gly
Ba
sic
[H+]
< [
OH]
Inc
rea
sin
gly
Ac
idic
[H+]
> [
OH]
H+ H+
H+
H+ H+
H+
H+
H+
OH
OH
H+
OH
H+
OH OH
OH OH H+
H+ H+
H+
OH OH
OH
OH OH OH
OH H+
11
12
13
14
47
48
pH Values
49
Buffers
• The internal pH of most living cells must remain close to pH 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+
50
51
Carbonic Acid
H2CO3
Bicarbonate ion
HCO3-
Carbonic acid-Bicarbonate buffer system
H+
OH+
52
Buffering Systems
How can your commute
affect coral reef growth
in the Caribbean
Sea?
53
Acidification: A Threat to Water Quality
• 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; this process is called ocean acidification
54
• 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
55
CO2
CO2 + H2O H2CO3
H+ + HCO3
H+ + CO32 HCO3
CaCO3 CO3
2 + Ca2+
H2CO3
56
(a) (b) (c)
57
• 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 pH lower than 5.2
• Acid precipitation damages life in lakes and streams and changes soil chemistry on land
58
59
More acidic
0
Acid rain
Normal rain
More basic
1
2
3
4
5
6
7
8
9
10
11
12
13
14