This lecture will help you understand: Environmental chemistry Building blocks of life Energy and energy flow Photosynthesis, respiration, chemosynthesis

This lecture will help you understand:

• Environmental chemistry

• Building blocks of life

• Energy and energy flow

• Photosynthesis, respiration, chemosynthesis

• Origin of life on Earth

• Early life

Central Case: Bioremediation of the Exxon Valdez Oil Spill

• The 1989 Alaskan spill was met with a massive cleanup.

• Scientists sprayed nitrogen and phosphorus on beaches to fertilize bacteria that could consume the oil.

• Results were mixed, but bioremediation was here to stay.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Chemistry and the environment

Chemistry is central to environmental science:

• Carbon dioxide and climate change

• Sulfur dioxide and acid rain

• Pesticides and public health

• Nitrogen and wastewater treatment

• Ozone and its atmospheric depletion


Bioremediation

One application of chemistry is in bioremediation, the use of plants or animals to clean up pollution.

From The Science behind the Stories

Rice University student Marc Burrell has researched how to get plants to take up toxic lead from contaminated soil.


Atoms and elements

An element is a fundamental type of chemical substance.

Elements are composed of atoms.

Each atom has a certain number of:

protons (+ charge)electrons (– charge)neutrons (no charge)


Atoms and elements

92 elements occur in nature, each with its characteristic number of protons, neutrons, and electrons.


Chemical symbols

Each element is abbreviated with a chemical symbol:

H = hydrogen

C = carbon

N = nitrogen

O = oxygen

P = phosphorus

Cl = chlorine

Fe = iron

Most abundant elements


Isotopes

Isotopes are alternate versions of elements, which differ in mass by having a different number of neutrons.

Carbon-14 has two extra neutrons beyond normal carbon’s 6.


Using isotopes in environmental science

Scientists have used isotopes to date ancient materials, reconstruct past climate, study the diet of animals, examine lifestyles of prehistoric humans, and track migrating birds and butterflies.

From The Science behind the Stories


Molecules, compounds, and bondsIons = electrically charged atoms or combinations of atoms

Molecules = combinations of two or more atoms

Compounds = molecules consisting of multiple elements

Atoms are held together by bonds:

covalent bond = uncharged atoms sharing electrons (CO2)

ionic bond = charged atoms held together byelectrical attraction

(NaCl)


Water is a unique compound

Hydrogen bonds give water properties that make it a vital molecule for life:

• Is cohesive

• Resists temperature change

• Ice insulates

• Dissolves many chemicals


Why ice floats on water

Stable hydrogen bonds in ice make it less dense than water, with its unstable hydrogen bonds.

ice

water

This allows ice to cover water bodies and protect them from freezing — a good thing for life in the water.


Water, the “universal solvent”

Water dissolves many chemicals.

Salt (NaCl) in seawater is broken up into sodium (Na+) and chloride (Cl–) ions.


Acidity

In an aqueous solution,

If H+ concentration is greater than OH– concentration,

then solution is acidic.

If OH– is greater than H +,

then solution is basic.


pH scale

pH scale measures acidity and basicity.

Pure water = 7

Acids < 7

Bases > 7


Organic compounds

Consist of carbon atoms and, generally, hydrogen atoms

Joined by covalent bonds

May include other elements

Highly diverse; C can form many elaborate molecules

Vitally important to life


Hydrocarbons

C and H only; major type of organic compound

Mixtures of hydrocarbons make up fossil fuels.


Macromolecules

Large molecules essential for life:

Proteins

Nucleic acids

Carbohydrates

Lipids

The first three are polymers, long chains of repeated molecules.


Proteins

Consist of chains of amino acids; fold into complex shapes

For structure, energy, immune system, hormones, enzymes


Carbohydrates

Complex carbohydrates consist of chains of sugars.

For energy, also structural (cellulose, chitin)


Lipids

Do not dissolve in water

• Fats and oils

• Phospholipids

• Waxes

• Steroids


Nucleic acids

DNA and RNA

Encode genetic information and pass it on from generation to generation

DNA = double-stranded chain (double helix)

RNA = single-stranded chain


Nucleic acids

Paired strands of nucleotides make up DNA’s double helix.


Genes and heredity

•Genes, functional stretches of DNA, code for the synthesis of proteins.


Cells

•Basic unit of organismal organization; compartmentalize macromolecules and organelles


Energy

•Can change position, physical composition, or temperature of matter

•Potential energy = energy of position

(water held behind a dam)

•Kinetic energy = energy of movement

(rushing water released from a dam)


Potential and kinetic energy

Potential energy stored in food is converted to kinetic energy when we exercise.


Laws of thermodynamics

First Law: Energy can change form, but cannot be created or lost.

Second Law: Energy will tend to progress from a more-ordered state to a less-ordered state (increase in entropy).


Increase in entropy

Burning firewood demonstrates the second law of thermodynamics.


Energy from the sun

•Energy from the sun powers most living systems.

Visible light is only part of the sun’s electromagnetic radiation.


Autotrophs and photosynthesis

The sun’s energy is used by autotrophic organisms, or primary producers (e.g., plants), to manufacture food.

Photosynthesis turns light energy from the sun into chemical energy that organisms can use.


Photosynthesis

In the presence of chlorophyll and sunlight,

Water and carbon dioxide

are converted to

sugars and oxygen.


Photosynthesis

6 CO2 + 12 H2O + energy from sun

————>

C6H12O6 (sugar) + 6 O2 + 6 H2O


Streamlined

6 CO2 + 6 H2O + energy from sun

————>

C6H12O6 (sugar) + 6 O2


Respiration and heterotrophs

Organisms use stored energy via respiration, which splits sugar molecules to release chemical energy.

This occurs in autotrophs and in the heterotrophs (animals, fungi, most microbes) that eat them.


Respiration

The equation for respiration is the exact opposite of the equation for photosynthesis.

C6H12O6 (sugar) + 6 O2

————>

6 CO2 + 6 H2O + chemical energy


Energy sources besides the sun

Geothermal energy comes from deep underground; radiation in Earth’s core heats the inside of the planet and rises to the surface (driving plate tectonics, volcanoes, etc.).Gravitational pull of the moon creates tidal energy.

Geyser powered by geothermal energy


Chemosynthesis

•Some organisms and communities live without sunlight and are powered by chemosynthesis.

6 CO2 + 6 H2O + chemical energy from H2S

————>

C6H12O6 (sugar) + 6 O2 + sulfates

(H2 S = hydrogen sulfide)


Hydrothermal vent communities

•Such communities include those at hydrothermal vents deep in the ocean. Recently discovered; bizarre organisms.


Origin of life on Earth

Early Earth was a hostile place; life had a challengingstart.


Fossil record

Fossil = imprint in rock of a dead organism

The fossil record teaches us much of what we know of life on the planet over the past 3.5 billion years.


Fossil record

The fossil record shows that:

• Species today are a tiny fraction of all that ever lived.

• Earlier organisms evolved into later ones.

• The number of species has increased through time.

• Episodes of mass extinction have occurred.

• Eukaryotes are only ~600 million years old.


History of life

By studying present-day organisms or their genes, we can infer relationships among organisms and decipher life’s history.

Life’s complete phylogeny is the “tree of life.”


How did life originate?

Several hypotheses are competing:

Heterotrophic hypothesis (primordial soup): interactions in early soup of organic chemicals

Extraterrestrial hypothesis (seeds from space): microbes from elsewhere arrived on meteorites

Chemoautotrophic hypothesis (life from the deep): first life from deep-sea hydrothermal vents


Conclusion:

Carbon-based life has flourished on Earth for over 3 billion years.

Scientists are trying to understand its origin.

Deciphering the origins of life requires understanding energy, energy flow, and chemistry.


Conclusion

Energy and chemistry are tied to nearly every important process in environmental science.

Chemistry can also be a tool for finding solutions to environmental problems.

Knowledge of chemistry is relevant to agriculture, water resource management, energy policy, toxicology, and climate change.


QUESTION: Review

Which of the following is a heterotroph?

a. Pine tree

b. Photosynthetic algae

c. Squid

d. Hydrogen sulfide


QUESTION: Review

The second law of thermodynamics states that…?

a. Energy cannot be created or destroyed

b. Things tend to move toward a less-ordered state

c. Matter tends to remain stable

d. Potential and kinetic energy are interchangeable


QUESTION: Review

Which of these does the fossil record NOT demonstrate?

a. There have been mass extinction episodes.

b. Most organisms that ever lived are now extinct.

c. Animals originated before plants, and plants before bacteria.

d. Numbers of species have increased through time.


QUESTION: Weighing the Issues

If there was an oil spill on your campus, would you recommend bioremediation?

a. Yes, because it is environmentally most desirable.

b. No, because it is less tested than traditional methods.

c. It depends. (on what factors…?)


QUESTION: Interpreting Graphs and Data

A molecule of the hydrocarbon ethane contains…?

a. 2 carbon atoms and 6 hydrogen atoms

b. 2 carbon molecules and 6 hydrogen enzymes

c. Carbon and hydrogen DNA

d. Eight different isotopes


QUESTION: Interpreting Graphs and Data

Which is listed from most acidic to most basic?

a. Ammonia, baking soda, lemon juice

b. Stomach acid, soft soap, HCl

c. Acid rain, NaOH, pure water

d. HCl, acid rain, ammonia


QUESTION: Viewpoints

How do you think life on Earth began?

a. With a mix of organic compounds in a primordial soup on Earth’s surface

b. With the entrance of microbes from other planets on meteorites falling to Earth

c. In deep-sea hydrothermal vents

Documents

This lecture will help you understand: Environmental chemistry Building blocks of life Energy and energy flow Photosynthesis, respiration, chemosynthesis