Matter, Energy, And Life

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27 Οκτ 2013 (πριν από 4 χρόνια και 13 μέρες)

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Chapter 3


Matter, Energy, And Life

Matter Is Made Of Atoms, Molecules,
And Compounds


Atom: simplest building block of chemicals


Element: a material composed of identical
atoms


Compound: a combination of atoms in a fixed
arrangement and proportion


Molecule: The simplest chemical unit of a
compound (O
2
, H
2
O, CH
4
,
C
6
H
12
O
6

etc.)


Many materials (
NaCl
) don’t have molecules

Chemical Formulas


Most Elements have symbols that are
common sense: H (Hydrogen), Si (Silicon), etc.


Some, known in ancient times, have symbols
from Latin: Fe (
F
errum

= Iron), Au (
Aurum

=
Gold), Na (
Natrium

= lye, for Sodium)


C
6
H
12
O
6

= Glucose = 6 Carbon, 12
Hydrogen, 6 Oxygen


SiO
2

= Quartz = 2 Oxygen for each Silicon

Electrical Charge Is An Important
Chemical Characteristic


Atoms contain three kinds of particles:


Protons (+) in the nucleus. Number of protons
determines what an element is


Neutrons (0) in the nucleus. Bind the nucleus
together


Electrons (
-
) orbiting the nucleus


Group together into shells


This is what interacts with other atoms


Atoms can gain or lose electrons and become
electrically charged (Ions)

Chemical Bonds Hold Molecules
Together


Ionic: Ions of opposite charge attract each
other. Example:
NaCl
, most minerals


Covalent: Atoms share electrons with
neighbors. Example: Most carbon chemicals


Metallic: Electrons wander freely between
atoms. Positive atoms held together by
negative electron “glue”


Hydrogen: H and O in water molecules
attracted to neighbors

Chemical Bonds Hold Molecules
Together


Ionic bonding holds most rocks and minerals
together


Covalent bonding holds living things together


Metallic bonding holds industrial civilization
together


Hydrogen bonding gives water its solvent and
heat
-
storing capacity

Elements Of Life


C, H, O, N, P, S are principal elements of life


Some elements like C can share more than
one electron with a neighbor (multiple
bonding)


Some elements like Fe and S can gain or lose
electrons in more than one way


These versatile atoms can be used for


Energy storage


Information storage


Triggering chemical reactions

Elements and Life


Some very abundant elements have no
biological uses (Al
, Si, Ti)


Some elements are essential in low amounts
but toxic at greater levels (Cu, Se)


Everything

is toxic at excessive levels


Some elements are toxic and have no
biological functions (Lead, Mercury)

The Elements

The Elements and Life

Organic Compounds Have A Carbon
Backbone


Organic compounds contain carbon as their
basic structural core


Chains (Petroleum)


Rings (Benzene, Toluene)


Simple carbon
-
bearing chemicals aren’t
considered Organic


CH
4
: Methane


CO
2
: Carbon Dioxide


CaCO
3
: Calcite, the Main Constituent of Limestone

Cells Are The Fundamental Units Of
Life


Cell Membrane: Contains contents and
processes, excludes foreign objects (mostly)


Nucleus: Where DNA resides


Simplest organisms lack nucleus


Mitochondria


Not to be confused with
Midichlorians

(MTFBWY)


Produce Energy for Cell


Have their own DNA


Probably originated as independent organisms

Energy


Energy Occurs In Different Types And Qualities


Thermodynamics Regulates Energy Transfers


Energy For Life


Extremophiles Live In Severe Conditions


Green Plants Get Energy From The Sun


Photosynthesis Captures Energy While Respiration
Releases That Energy

Thermodynamics Regulates Energy
Transfers


First Law: Energy is Not Created or Destroyed


Can Change Form


Matter and Energy can be converted


Second Law:
Entropy

increases


Entropy is often likened to disorder but is not
entirely the same


Entropy can decrease at expense of surroundings

From Species To Ecosystems


Organisms Occur In Populations,
Communities, And Ecosystems


Food Chains, Food Webs, And Trophic Levels
Link Species


Ecological Pyramids Describe Trophic Levels


Waterworld




Sometimes It Looks More Like This

Reasons to be a ”Water chauvinist".


Stays liquid over a wide range of
temperatures.


Polar or asymmetrical molecule. Attracts ions
easily
-

Good transporter of nutrients


Does not dissolve organic molecules (so we do
not dissolve in our own cell fluids)

Material Cycles And Life Processes


Sources: supply elements for life and physical
processes


Example: Burning vegetation releases CO
2


Sinks: remove materials from environment


Example: Plants remove CO
2

from the air


Limestone removes CO
2

from the air


Residence Time: How long an average atom or
molecule remains in a system


Example: Water molecule in air, 10 days

Material Cycles on the Earth


The Hydrologic Cycle Moves Water Around
The Earth


Oceans


Atmosphere


Land
-

Ocean


Nutrient Cycles


Ultimate Source: Rocks


Released by Weathering


Taken up by Biosphere


Transported by Water or Atmosphere


Sinks: Atmosphere, Deep Oceans, Rocks


Reasons to be a "Carbon chauvinist".


Can bond to four neighboring atoms


Can bond to other carbon atoms, sharing one,
two, or three electrons


These properties make it possible to form a
vast array of organic molecules


No other element has these properties

Carbon in the Earth


Volcanoes emit carbon dioxide


Carbonate rocks lock up carbon dioxide


Ancient biomass locked up carbon as coal,
petroleum, natural gas

Carbon in the Biosphere

Plants use sunlight, H
2
O, CO
2

to create organic
molecules:


6 H
2
O + 6 CO
2

+ energy




C
6
H
12
O
6

(glucose) + 6O
2
(toxic waste)

Animals run the reactions in reverse:


C
6
H
12
O
6

(glucose) + 6O
2




6 H
2
O + 6 CO
2

+ energy


Also use organic molecules directly (vitamins)

Carbon Cycles


Plant


Animal Cycle


Decay returns CO
2

to atmosphere


Marine organisms fix CO
2

in carbonate rocks


Weathering returns CO
2

to atmosphere


Some C fixed in rocks long
-
term as carbonates
or fossil fuel


Humans burn fossil fuel and add (not return)
CO
2

to atmosphere

The Carbonate
-
Silicate Cycle


Earth has almost as much carbon dioxide as
Venus


Volcanoes add carbon dioxide to the
atmosphere


Mountain
-
building favors cooling


Carbon dioxide is removed from the air to
make carbonate rocks


“Icehouse” and “Greenhouse” episodes

The Paradox of Nitrogen


It makes up 79% of the atmosphere


Most plants cannot use N
2


Nitrogen converted to usable forms by
specialized microorganisms


Human use of nitrogen


Nitrogen
-
fixing plants (Legumes)


Natural fertilizers (Guano, Nitrate Minerals)


Synthetic nitrates (Haber Process)


Sulfur in the Earth


Sulfide minerals: ores, pyrite


Volcanic emissions: H
2
S, SO
2


Coal: pyrite, organic sulfur


Petroleum: organic sulfur

From Earth to Environment


Volcanic emissions: H
2
S, SO
2


Microbial action


Weathering


Natural exposures


Mine waste


Smelting


Fossil Fuels

Acid Rain


S + O
2

= SO
2

(sulfur dioxide)


2SO
2

+ O
2

= 2SO
3

(sulfur trioxide)


SO
3

+ H
2
O = H
2
SO
4

(sulfuric acid)


Forms by smelting or burning fossil fuels

Acid Rain


pH: Measure of acidity


0 = extremely acid (Muriatic Acid)


7 = neutral


14 = extremely alkaline (Lye)


Normal water in air is 5.5 (Carbonic Acid)


Acid rain can be pH 3 or less


Ca

and Mg neutralize acid (Limestone,
Dolomite, some volcanic rocks)


Rocks poor in
Ca

and Mg cannot neutralize
acid (Granite)

Phosphorus in the Earth


Most common limiting factor for life


Mostly in apatite Ca
5
(
Cl,F
)(PO
4
)
3


Granites


Phosphate Rock (recycled biological P)


Released by:


Weathering


Mining (for fertilizer)

Phosphorus on Land


Phosphorus in Soil


Uptake by plants


Consumption by animals


Return to soil via plant and animal waste,
decay


Some lost by runoff

Phosphorus in Water


Essential to aquatic life


Excess causes eutrophication


Runaway productivity, excess oxygen demand


Return to water via plant and animal waste,
decay


Some ends up in sediments (Chitin, Bone)


Sedimentary P returns to land via uplift, plate
tectonics


Human
-
Applied P goes to Oceans (Sink)

Distinctive Aspects of the P Cycle


No Atmospheric Component


Geologic Portion of Cycle Very Slow


Mostly involves biological transfers


P in oceans not recycled quickly


Human use: Rocks


Fertilizer


Oceans


Not Recycled


Peak Phosphorus?


Phosphorus (Fertilizer)


Morocco, China, South Africa, Jordan, U.S. =
90
% of World Reserves