CHAPTER 2 COLLEGE ENVIRONMENTAL SCIENCE Basics Review

Matter Matter: all material in the universe that has mass and occupies space  It can be solid, liquid, or gas Law of conservation of matter: matter can be transformed from one type of substance into others  But it cannot be destroyed or created Because the amount of matter stays constant  It is recycled in nutrient cycles and ecosystems  We cannot simply wish pollution and waste away

Elements Element: a fundamental type of matter  A chemical substance with a given set of properties  Examples: nitrogen, phosphorus, oxygen  92 natural and 20 artificially created elements exist Nutrients: elements needed in large amounts by organisms  Examples: carbon, nitrogen, calcium

Atoms Atoms: the smallest components that maintain an element’s chemical properties The atom’s nucleus (center) has protons (positively charged particles) and neutrons (lacking electric charge)  Atomic number: the number of protons Electrons: negatively charged particles surrounding the nucleus  Balance the protons’ positive charge

The structure of an atom

Isotopes and ions Isotopes: atoms of an element with different numbers of neutrons Mass number: the number of protons + neutrons Isotopes of an element behave slightly differently Ions: atoms that gain or lose electrons  They are electrically charged

Some isotopes are radioactive and decay Radioactive isotopes shed subatomic particles and emit high-energy radiation  They decay until they become nonradioactive stable isotopes Half-life: the amount of time it takes for one-half of the atoms in a radioisotope to give off radiation and decay  Different radioisotopes have different half-lives ranging from fractions of a second to billions of years  Uranium-235, used in commercial nuclear power, has a half-life of 700 million years

Molecules and compounds An attraction for each other’s electrons bonds atoms Molecules: combinations of two or more atoms Chemical formula: indicates the type and number of atoms in the molecule (oxygen gas: O 2 ) Compound: a molecule composed of atoms of two or more different elements  Water: two hydrogen atoms bonded to one oxygen atom: H 2 O  Carbon dioxide: one carbon atom with two oxygen atoms: CO 2

Atoms are held together with bonds Ionic bonds: ions of different charges bind together  Table salt (NaCl): the Na + ion is bound to the Cl – ion Covalent bond: atoms without electrical charges “share” electrons  Example: hydrogen atoms share electrons – H 2 Solutions: electrons, molecules and compounds come together with no chemical bonding  Air contains O 2, N 2, H 2 O, CO 2, methane (CH 4 ), ozone (O 3 )  Human blood, ocean water, plant sap, metal alloys

Ionic bonds Animation: Ionic Bonds Right-click / Select “Play”

Covalent bonds Animation: Covalent Bonds Right-click / Select “Play”

Hydrogen ions determine acidity Water can split into H + and OH – The pH scale quantifies the acidity or basicity of solutions Acidic solutions: pH < 7  Contain more H + Basic solutions: pH > 7  Contain more O H – Neutral solutions: pH: 7 A pH of 6 contains 10 times as many H + as a pH of 7

Matter is composed of compounds Living things depend on organic compounds Organic compounds: carbon atoms bonded together  They may include other elements: nitrogen, oxygen, sulfur, and phosphorus Carbon can be linked in elaborate chains, rings, other structures  Forming millions of different organic compounds Inorganic compounds: lack the carbon–carbon bond

Carbon skeletons Animation: Carbon Skeletons Right-click / Select “Play”

Polysaccharides Animation: Polysaccharides Right-click / Select “Play”

Hydrocarbons Hydrocarbons: organic compounds that contain only carbon and hydrogen  The simplest hydrocarbon is methane (natural gas) Fossil fuels consist of hydrocarbons  Crude oil contains hundreds of types of hydrocarbons

Macromolecules are building blocks of life Polymers: long chains of repeated organic compounds  Play key roles as building blocks of life Three essential types of polymers:  Proteins  Nucleic acids  Carbohydrates Lipids are not polymers, but are also essential  Fats, oils, phospholipids, waxes, steroids Macromolecules: large-sized molecules essential to life

Proteins are long chains of amino acids Proteins comprise most of an organism’s matter They produce tissues, provide structural support, store energy, transport material Animals use proteins to generate skin, hair, muscles, and tendons Some are components of the immune system or hormones (chemical messengers) They can serve as enzymes: molecules that promote (catalyze) chemical reactions

Nucleic acids direct protein production Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) carry hereditary information of organisms Nucleic acids: long chains of nucleotides that contain sugar, phosphate, and a nitrogen base Genes: regions of DNA that code for proteins that perform certain functions

DNA and RNA structure Animation: DNA and RNA Structure Right-click / Select “Play”

DNA double helix Animation: DNA Double Helix Right-click / Select “Play”

Carbohydrates and lipids Carbohydrates: include simple sugars and large molecules of simple sugars bonded together Glucose fuels cells and builds complex carbohydrates Plants store energy in starch, a complex carbohydrate  Animals eat plants to get starch Organisms build structures from complex carbohydrates  Chitin forms shells of insects and crustaceans  Cellulose found in cell walls of plants Lipids do not dissolve in water  Fats and oils (energy), waxes (structure), steroids

Cells compartmentalize macromolecules All living things are composed of cells: the most basic unit of organismal organization Cells vary in size, shape, and function  They are classified according to their structure Eukaryotes: plants, animals, fungi, protists  Contain a membrane-enclosed nucleus  Their membrane-enclosed organelles do specific things Prokaryotes: bacteria and archaea  Single-celled, lacking membrane-enclosed nucleus and organelles

Energy fundamentals Energy: an intangible phenomenon that can change the position, physical composition, temperature of matter  Involved in biological, chemical, physical processes Potential energy: energy of position Kinetic energy: energy of motion Chemical energy: potential energy held in the bonds between atoms Changing potential into kinetic energy  Releases energy  Produces motion, action, or heat

Potential vs. kinetic energy Potential energy stored in our food becomes kinetic energy when we exercise and releases carbon dioxide, water, and heat as by-products Insert Figure 2.11

Energy is conserved but changes in quality First law of thermodynamics: energy can change form but cannot be created or destroyed Second law of thermodynamics: energy changes from a more-ordered to a less-ordered state  Entropy: an increasing state of disorder Living organisms resist entropy by getting energy from food and photosynthesis  Dead organisms get no energy and through decomposition lose their organized structure

The sun’s energy powers living systems Energy that powers Earth’s ecological systems comes mainly from the sun The sun releases radiation from the electromagnetic spectrum  Some is visible light

Using solar radiation to produce food Autotrophs (producers): organisms that use the sun’s energy to produce their own food  Plants, algae, cyanobacteria Photosynthesis: the process of turning the sun’s light energy into high- quality chemical energy  Sunlight converts carbon dioxide and water into sugars  Moving to lower entropy

6CO 2 + 6H 2 O + sun’s energy C 6 H 12 O 6 (sugar) + 6O 2 Photosynthesis produces food Chloroplasts: organelles where photosynthesis occurs  Contain chlorophyll: a light-absorbing pigment  Light reaction: solar energy splits water and creates high-energy molecules that fuel the …  Calvin cycle: links carbon atoms from carbon dioxide into sugar (glucose)

Light and pigments Animation: Light And Pigments Right-click / Select “Play”

Cellular respiration releases energy It occurs in all living things (plants, animals, etc.) Organisms use chemical energy created by photosynthesis  Oxygen breaks the high-energy chemical glucose bonds  The energy is used to make other chemical bonds or tasks Heterotrophs: organisms that gain energy by feeding on others  Animals, fungi, microbes  The energy is used for cellular tasks C 6 H 12 O 6 (sugar) + 6O 2 6CO 2 + 6H 2 O + energy