CHAPTER 4: From Chemistry to Energy to Life
I. Central Case: Bioremediation of the Exxon Valdez Oil Spill
A. The tanker Exxon Valdez struck a reef on March 24, 1989, in Alaska= s Prince William Sound and spilled 11 million gallons of crude oil.
B. Thousands of workers employed by Exxon, with government agencies and volunteers, tackled the spill with conventional methods.
C. Scientists used the opportunity to test a new way of cleaning up the spill by enlisting bacteria to naturally break down the oil in a process called bioremediation.
1. Although the bacteria were presented with an abundant new food source, they were not immediately able to consume it because the oil contained too much carbon and not enough nitrogen and phosphorus.
2. Scientists applied a fertilizing mixture containing nitrogen and phosphorus.
3. Because there were many complicating factors, experts have debated how much the treatments sped up degradation.
II. Chemistry and the Environment
A. Examine many environmental issues, and you will likely discover chemistry playing a central role; chemistry is also central to developing solutions.
B. Atoms and elements are the chemical building blocks.
1. An element is a fundamental type of matter that cannot br broken down into substances with other properties.
2. Elements are composed of atoms, the smallest components of an element that maintain the chemical properties of that element.
3. Every atom has a nucleus of protons (positively charged particles) and neutrons (particles lacking electric charge); the atomic number of the element is the number of protons each atom contains, and the mass number is the combined number of protons and neutrons.
4. An atom= s nucleus is surrounded by negatively charged particles known as electrons, which balance the positive charge of the protons.
5. Although all the atoms of an element have the same atomic number and the same number of protons, they may not contain the same number of neutrons; these atoms are called isotopes, and they have different mass numbers.
6. Because isotopes differ slightly in mass, they also differ slightly in their behavior; researchers have used this to study many phenomena both in and out of the lab.
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7. Some isotopes shed subatomic particles (decay) and emit high-energy radiation as they do so; they are called radioisotopes and are radioactive.
8. Each radioisotope decays at a particular rate called the half-life, or the amount of time it takes for one-half the atoms to give off radiation and decay.
9. Atoms may also gain or lose electrons to become ions, which are electrically charged. An ion may consist of a single charged atom or be a combination of two or more atoms from one or more elements.
C. Atoms bond to form molecules and compounds.
1. Atoms can bond together in chemical reactions to form molecules, combinations of two or more atoms.
2. If atoms in a molecule are composed of two or more different elements, the molecule is called a compound.
3. Atoms are held together in molecules by chemical bonds, ionic bonds, or covalent bonds.
a. When atoms in a molecule share electrons, they have a covalent bond.
b. If one atom exerts a greater pull, then one or more electrons may be transferred from an atom of one element to an atom of another element; this creates two oppositely charged ions and forms an ionic bond.
c. These associations of ions are not considered molecules, but instead are called ionic compounds, or salts..
4. Elements, molecules, and compounds can come together without chemical bonding in a substance called a mixture.
D. The chemical structure of the water molecule facilitates life.
1. The water molecule is a single oxygen atom that bonds to two hydrogen atoms at a 105-degree angle; the attraction of the oxygen for the electrons of the hydrogen atoms results in a polar molecule with slight charges.
2. Because of the slight charge on each molecule, water molecules can adhere to one another in a special type of interaction called a hydrogen bond.
3. Hydrogen bonding gives water the properties important to supporting life and stabilizing Earth= s climate.
E. Hydrogen ions determine acidity.
1. Water molecules occasionally dissociate, forming a hydrogen ion (H+) and a hydroxide ion (OH-).
2. Solutions in which the H+ concentration is greater than the OH- concentration are acidic, while solutions in which the OH- concentration is greater than the H+ concentration are basic.
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3. The pH scale was devised to quantify the acidity or basicity of solutions, and runs from 0 to 14, with 0 to 7 being acidic, 7 being neutral, and 7 to 14 being basic.
F. Matter is composed of organic and inorganic compounds.
1. Organic compounds consist of carbon atoms and, generally, hydrogen atoms that are joined together by covalent bonds, and may include other elements.
2. Hydrocarbonds contain only atoms of carbon and hydrogen.
3. Bacteria used in bioremediation of petroleum spills degrade hydrocarbons into simpler molecules.
G. Macromolecules are building blocks of life.
1. Polymers are long chains of repeated molecules, and three
polymers-proteins, nucleic acids, and carbohydrates-play key roles
as building blocks of life.
2. Lipids are not considered polymers but are also fundamental to life. Four types of molecules - proteins, nucleic acids, carbohydrates, and lipids - are referred to as macromolecules because of their large size.
3. Proteins are made up of long chains of amino acids, each of which is made up of a central carbon linked to a hydrogen atom, an acidic carboxyl group (-COOH), a basic amine group (-NH2), and an organic side chain unique to each type of amino acid. Proteins provide structure, transport substances, defend against invaders, carry messages, and promote certain chemical reactions.
4. Nucleic acids are molecules that carry the hereditary information for organisms and direct the production of proteins.
a. Deoxyribonucleic acid (DNA) is a double-stranded spiral that contains the hereditary information.
b. Ribonucleic acid (RNA) is usually a single strand that contains information from a small portion of a DNA molecule and uses it to direct the building of proteins.
c. Regions of DNA that code for particular proteins that perform particular functions are called genes.
5. Carbohydrates are organic compounds consisting of carbon, hydrogen, and oxygen atoms in the ratio of about 1 carbon to 2 hydrogen to 1 oxygen; they are used for energy and to build structures such as leaves, lobster shells, and fingernails.
6. Lipids are a fourth type of macromolecule, but are not polymers and do not dissolve in water; they include fats, phospholipids, waxes, and steroids. Lipids are used for energy storage, membranes, and hormones.
H. Organisms use cells to compartmentalize macromolecules.
1. All living things are composed of cells, the most basic units of organization.
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2. Biologists classify organisms into two groups based on the structure of their cells.
a. Eukaryotic organisms have cells with organelles (internal
structures that perform specific functions), including a nucleus.
b. Prokaryotic organisms are generally single-celled and lack
organelles and a nucleus.
III. Energy Fundamentals
A. Energy can change the position, physical composition, or temperature of matter.
1. There are two fundamental types of energy.
a. Potential energy is the energy of position.
b. Kinetic energy is the energy of motion.
2. Chemical energy is a special type of potential energy that is held in the bonds between atoms.
B. Energy is always conserved . . .
1. The first law of thermodynamics states that energy can change from one form to another, but cannot be created or lost.
C. But energy changes in quality.
1. The second law of thermodynamics states that energy tends to change from a more-ordered state to a less-ordered state.
2. In every transfer of energy, some usable energy is lost; the degree of disorder in a substance, system, or process is called entropy.
3. The order of an object or system can be increased through the input of additional energy from outside the system.
D. Light energy from the sun powers most living systems.
1. The sun supplies energy to those organisms that are able to use it to produce their own food; they are autotrophs, or primary producers.
2. Autotrophs turn light energy from the sun into chemical energy in a process called photosynthesis.
3. In photosynthesis, sunlight powers a series of chemical reactions that convert water and carbon dioxide into sugars and oxygen, providing high-quality energy that the organism can use.
E. Photosynthesis produces food for plants and animals.
F. Cellular respiration releases chemical energy.
1. The chemical energy created by photosynthesis can later be used by organisms in the process of cellular respiration.
2. Cells use the reactivity of oxygen to convert glucose back into its original starting materials, water and carbon dioxide, and release energy to perform tasks within cells.
3. This extraction of energy occurs in both autotrophs and heterotrophs, or consumers.
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G. Geothermal energy also powers Earth= s systems.
1. The gravitational pull of the moon causes tides, providing low-quality energy.
2. A more significant additional energy source is the radiation from radioactive elements deep in the Earth; this heats the interior of the planet, causing volcanoes and hot water geysers, and producing geothermal energy.
H. Hydrothermal vent communities utilize chemical energy instead of light energy.
1. Hydrothermal vents are areas in the deep ocean from which jets of geothermally heated water emerge.
2. Communities of living organisms at these locations depend on bacteria at the base of the food web; these bacteria fuel themselves by chemosynthesis, producing sugars.
IV. The Origin of Life
A. Early Earth was a very different place.
B. Several hypotheses have been proposed to explain life= s origin.
1. Primordial soup: The hererotrophic hypothesis
a. This is the idea that life evolved from a primordial soup of simple inorganic chemicals - carbon dioxide, oxygen, and nitrogen - dissolved in the ocean.
b. Lab experiments have provided evidence that the proposed process could work.
2. Seeds from space: The extraterrestrial hypothesis
a. This is the idea that bacteria from space crashed to Earth on meteorites and started life here.
b. The Murchison meteorite, which fell in Australia in 1969, contained many amino acids.
3. Life from the depths: The chemoautotrophic hypothesis.
a. This is the idea that early life was found in deep-sea vents where sulfur was abundant.
b. Some of the most ancient ancestors of today= s life forms likely lived in extremely hot and wet environments.
C. Self-replication and cell formation were crucial steps.
D. The fossil record has taught us much about life= s history.
1. The earliest evidence of life on Earth comes from 3.5-billion-year-old rocks.
2. Fossils are imprints of dead organisms in stone; fossils provide information about plants and animals in different time periods.
3. The fossil record is the cumulative set of fossils worldwide.
a. The species living today are but a tiny fraction of all the species that have ever lived.
b. Earlier types of organisms changed, or evolved, into later ones.
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c. The number of species existing at any one time has increased through history.
d. There have been several episodes of mass extinction, or simultaneous loss of great numbers of species.
e. Many organisms present early in history were smaller and simpler than modern organisms.
E. Present-day organisms and their genes also help us decipher life= s history.
A. Deciphering how life originated depends in part on understanding energy, energy flow, and chemistry.
B. Energy and chemistry are tied to nearly every significant process in environmental science.
C. Chemistry can be a tool for finding solutions to environmental problems.
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