What are the Different Forms of Matter?

• Matter: anything that has mass and occupies space • Elements: pure substances that cannot be broken down chemically into simpler forms of matter – Some share properties and reactivity  grouped (Dmitri Mendeleyev, 1869); symbols used ( see Periodic Table of Elements ) – About 30 are important for living things ( see handout ); carbon, oxygen, hydrogen, and nitrogen ≈ 90% mass of living things • Atom: simplest particle that retains all the properties of the particular element (atomic structure a “model”) – Nucleus: consists of protons (+) and neutrons (neutral) of equal mass (atomic number = number of protons = element’s identity) – Electrons (-): low mass, arranged in shells around nucleus (outer shells reactive, high energy, can be attracted to other nuclei) – Isotopes: different forms of same element (re. number of neutrons) – Ions: charged atoms (lose electron  cation; gain electron  anion)

How do Atoms Combine to Make Compounds?

• Compound: pure substance made up of two or more elements (vs. mixtures of multiple compounds) • Chemical Bonds: elements with unfilled outer shells reactive (stable octet; Noble gases not reactive) – Elements valence (number of bonds will form) determined by the number of outer-shell electrons (= group number) • Example: carbon (group IV) forms four bonds, often with other carbon atoms, forming chains and rings • Groups 5-7 form 3 bonds, 2 bonds, and 1 bond, respectively – Ionic Bond: transfer of electron from one element to another (from opposite sides of Periodic Table), and subsequent attraction between resulting cation (+) and anion (-); salts (ex. NaCl) – Covalent Bond: sharing of electrons between multiple nuclei  molecules; example: H 2 O (water) • Intermolecular Forces: between (vs. within) molecules – Hydrogen Bond: attraction between partial positive H atom (of one molecule) and unbound electrons or partial negative atom (of a separate molecule)

How are Matter and Energy Related?

• Energy: ability to do work or cause change • States of matter: solid, liquid, and gas

– All compounds transition at specific temperatures (melting and boiling points) – From solid to gas, atoms/molecules increase in motion, and distances increase (Brownian Motion: atoms and molecules always in motion  can meet and react)

• Energy and Chemical Reactions

– Chemical reactions involve breaking and forming of chemical bonds (movement/transfer of electrons) – Reaction Equations: reactants  products • Example: CO 2 + H 2 O  H 2 CO 3 – Catalysts: lower activation energy of reactions; re-used – Redox Reactions: involve loss (oxidation) or gain (reduction) of electrons (ex., electron transport chains)

Why is Water so Important for Life?

• Properties of Water (favorable for life)

– Good solvent: water is polar (negative and positive ends)  breaks ionic bonds and makes ions available for organisms (ex. calcium from calcium carbonate, sodium from sodium chloride) – Cohesive: molecules of water “stick together” (results from hydrogen bonds)  good medium for chemistry and high surface tension • Top mm of ocean/lakes with highest abundance of photosynthetic microbes, many organisms can float on surface – High thermal capacity: resists temperature changes; stable for life – Unique density: becomes less dense upon freezing (ice floats); allows life to exist under ice when air is far below freezing

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What are Mixtures, Solutions, Acids, and Bases?

• Mixtures: combinations of multiple substances • Solutions: mixture where one or more substances (solutes) are uniformly distributed in another substance (solvent) – Example: seawater (water: 96.5%, salts: about 3.5%, plus dissolved gases and organic matter) • Acids, Bases, and the pH Scale – Acid: any substance that increases the concentration of protons (H + ) in solution (increases hydronium ion, H 3 O + ); sour tastes, corrosive • Examples: sulfuric, nitric, hydochloric acids – Base: any substance that decreases proton concentration (or increases hydroxide ion, OH ) in solution; bitter tastes, feel slippery, but can be as dangerous as acids when concentrated • Examples: sodium hydroxide, calcium carbonate – pH Scale: measurement of proton concentration (natural logarithm); relative degree of acidity/basicity • Ranges from 0 to 14; 7 is neutral (pure water), <7 acids, >7 bases • Buffers: substances that stabilize pH changes

What are the Major Groups of Biochemicals?

• Organic Chemicals: have carbon; methane (CH space urea (CH 4 N 2 O) from simpler compounds • Major groups of organic biochemicals • Main sources of metabolic energy for living things – Lipids: large proportion of C-C and C-H bonds pigments, and steroid hormones bases, a sugar, and an inorganic phosphate group) • Hereditary (DNA, RNA) and energy (ATP) functions 4 ) simplest – Life on Earth based on carbon compounds; several identified in outer – Vital Force Theory (organic compounds only produced by living organisms) disproved in 1828 when Frederick Wöhler synthesized – Carbohydrates: monosaccharides (ex. glucose), disaccharides (ex. sucrose), polysaccharides (examples: starch, glycogen, cellulose) • Component of cell membranes; energy sources, natural fats, oils, – Proteins: polymers of amino acids (20 types); many functions: • Enzymes (organic catalysts), structural functions, antibodies, cell recognition and messenger molecules (hormones and receptors) – Nucleic Acids: polymers of nucleotides (characterized by nitrogenous

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What are Condensation and Hydrolysis Reactions?

• Polymerization – Condensation of monomers – Examples: glucose  acids  proteins  polymers and water (by-product) starch (or cellulose, or glycogen); amino • Hydrolysis – Polymers + water involved)  subunits – Example: digestion of proteins or polysaccharides (enzymes • Energy Currency – Adenosine triphosphate (ATP) is the molecule involved in the transfer of energy for most metabolic reactions (ATP  ADP  AMP or vice versa) – Other energy compounds: NADH, NAD, FADH (redox factors) – All reactions require energy, but can produce a net gain in energy (or can require net energy input from another source)

The Origin of Life: How? When? Where?

• • 1.

2.

3.

From the Pre-biotic Soup to Proto-cells (Oparin-Haldane) Formation of large organic compounds from “interstellar-type” compounds (amino acids formed from methane, water, ammonia, and hydrogen gas with electric spark as energy source - Stanley Miller, 1953) Formation of organic polymers (biochemicals) from large organic compounds (some polymerize in presence of metal catalysts, but small yields) Internalization of metabolites within lipid membrane (phospho lipids and fatty acids spontaneously form hollow spheres in water, and internalize certain compounds) – – The Importance of RNA RNA a simpler compound than DNA, can do cellular work (like an enzyme), and can evolve in response to selection Ribosomal RNA is conserved in all living things; RNA nucleotides involved in the energy systems of all cells (ex., ATP)

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The Origin of Life: How? When? Where?

• The Heterotroph Hypothesis: first living cells were likely heterotrophic vs. autotrophic (complex metabolism) • The Fossil Record for Early Life – Oldest confirmed fossils of cells ~ 2 billion years old (stromatolites); older fossils (~ 3.5 billion years old) relatively controversial – Indirect indications of life (bioindicators) suggest life present by 3.5 billion years ago • Graphite particles rich in carbon-12 from rocks in Greenland • Banded iron formations (redbeds) suggest that oxygen gas reached ~ 15% of present-day level by 2.5 billion years ago (regarding formation of rust in presence of iron, water, and oxygen gas) • Where did Life Originate?

– Pre-biotic soup (“warm little pond” or “cold pond”?); water is the “matrix of life” (properties conducive for life) – Hydrothermal vents and springs: both home to ancient forms of microbes (chemosynthetic thermophiles) – Panspermia Hypothesis: first cells arrived via meteorite?

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Is There Life in Outer Space?

• The Search for Life in Outer Space (astrobiology) – Existence of extra-terrestrial microbes thought to be more likely than in past, due to diversity of extremophiles on Earth (“life finds a way”), and presence of organic compounds, water, and energy sources in outer space (vs. “Goldilocks argument”) • Bacteria omnipresent: found in all extreme environments on Earth – Temperature: -2 to 121 and from crustal fluids ° C (ice caps, hydrothermals; experimental evidence) – Pressure: up to 1600 MPa (experimental); microbes cultured from deep-sea – Dryness: endolithic microbes in deserts of Peru and Antarctica (0% humidity) – Salinity: 15-37% NaCl (soda lakes) – pH: as low as 0.7 (sulfur springs) and as high as 12.5 (soda lakes) – Locations of Interest: Mars (polar ice caps, recent evidence of more widespread water in past); Europa (Jovian moon – “snowball” with liquid beneath ice, likely volcanic activity and magnetic field) • The Search for

Intelligent

Life in Outer Space – Search for Extra-Terrestrial Intelligence (SETI) • Drake Equation: formulated by Frank Drake in 1961 as an estimate of the number of communicating civilizations in the Milky Way galaxy; estimates range from 1 to 1,000,000 (C. Sagan); Drake’s ~ 10 • Listen for abnormal signals of extra-terrestrial origins via radio telescopes; digital signals sent out in 1974 and 1999; Voyager spacecraft (2) contain messages on discs (now beyond solar system); SETI@home project allows individuals to help analyze data (noise)