Chapter 2 Chemistry Comes Alive

Chapter 2 Chemistry Comes Alive Matter • Anything that has mass and occupies space • States of matter: • Solid— • Liquid— • Gas—

Forms of Energy • Chemical energy— • Electrical energy— • Mechanical energy— • Radiant or electromagnetic energy—exhibits wavelike properties (i.e., visible light, ultraviolet light, and X-rays)

Major Elements of the Human Body • • • • • About 3.9% of body mass: • Calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (Cl), magnesium (Mg), iodine (I), and iron (Fe) • < 0.01% of body mass: • Part of enzymes, e.g., chromium (Cr), manganese (Mn), and zinc (Zn)

Radioisotopes • Spontaneous decay (radioactivity) • Similar chemistry to stable isotopes • Can be detected with scanners • Valuable tools for biological research and medicine • Cause damage to living tissue: • • Radon from uranium decay causes lung cancer Molecules and Compounds • Most atoms combine chemically with other atoms to form molecules and compounds • Molecule— • Compound—

Chemically Reactive Elements • Outermost energy level ______• Tend to ______(form bonds) with other atoms to achieve stability

Ionic Bonds • Ions are formed by transfer of valence shell electrons between atoms • Anions ______• Cations ______• Attraction of opposite charges results in an ionic bond

Covalent Bonds • • Allows each atom to fill its valence shell at least part of the time

Covalent Bonds • Sharing of electrons may be equal or unequal • Equal sharing produces ______

• CO2 • Unequal sharing by atoms ______

• H2O • Atoms with six or seven valence shell electrons are electronegative, e.g., oxygen • Atoms with one or two valence shell electrons are electropositive, e.g., sodium

Hydrogen Bonds •

• Common between dipoles such as water • Also act as intramolecular bonds, holding a large molecule in a three-dimensional shape

Chemical Reactions • Occur when chemical bonds are ______• Represented as chemical equations • Chemical equations contain: • • Relative amounts of reactants and products, which should balance

Patterns of Chemical Reactions • Synthesis (combination) reactions • • Decomposition reactions • • Exchange reactions •

Chemical Reactions • All chemical reactions are either exergonic or endergonic • Exergonic reactions— • Catabolic reactions • Endergonic reactions— • Anabolic reactions

Chemical Reactions • All chemical reactions are theoretically ______• A + B  AB • AB  A + B • Chemical equilibrium occurs if neither a forward nor reverse reaction is dominant • Many biological reactions are essentially irreversible due to • Energy requirements • Removal of products

Rate of Chemical Reactions • Rate of reaction is influenced by: • • • • Catalysts:  rate without being chemically changed •

Classes of Compounds • Inorganic compounds • • Do not contain ______• Organic compounds • • Contain ______Water • • Most important inorganic compound in living organisms because of its properties • Properties • High heat capacity • Absorbs and releases heat with little temperature change • • High heat of vaporization • Evaporation requires large amounts of heat •

Properties of Water • Polar solvent properties • • Forms hydration layers around large charged molecules, e.g., proteins (colloid formation) •

Properties of Water • • A necessary part of hydrolysis and dehydration synthesis reactions • • Protects certain organs from physical trauma, e.g., cerebrospinal fluid

Acids and Bases • Both are electrolytes • • HCl  H+ + Cl–

Acids and Bases • • NaOH  Na+ + OH– • OH– accepts an available proton (H+) • – + OH + H  H2O • ______are important bases in the body

Acid-Base Concentration • • As [H+] increases, acidity increases • • As [H+] decreases (or as [OH–] increases), alkalinity increases

pH: Acid-Base Concentration • pH = the negative logarithm of [H+] in moles per liter • Neutral solutions: • • pH of pure water = pH 7: [H+] = 10 –7 M • pH: Acid-Base Concentration • Acidic solutions • • • pH scale is logarithmic: a pH 5 solution has 10 times more H+ than a pH 6 solution • Alkaline solutions • •

Acid-Base Homeostasis • pH change interferes with cell function and may damage living tissue • Slight change in pH can be fatal •

Buffers • • Convert strong (completely dissociated) acids or bases into weak (slightly dissociated) ones • Carbonic acid-bicarbonate system

Organic Compounds • • Unique to living systems • Include ______

Organic Compounds • Many are polymers—chains of similar units (monomers or building blocks) • •

Carbohydrates • Sugars and starches

• Contain C, H, and O [(CH20)n] • Three classes • • •

Lipids • Contain C, H, O (less than in carbohydrates), and sometimes P • Insoluble in water • Main types: • • • •

Triglycerides • Neutral fats—solid fats and liquid oils • Composed of three fatty acids bonded to a glycerol molecule • Main functions • • • Protection

Saturation of Fatty Acids • Saturated fatty acids • ______; maximum number of H • • Unsaturated fatty acids • • Reduced number of H atoms •

Phospholipids • Modified triglycerides: • Glycerol + two fatty acids and a phosphorus (P)-containing group • “Head” and “tail” regions have different properties • Steroids • Steroids— • Cholesterol, vitamin D, steroid hormones, and bile salts

Eicosanoids • Many different ones • Derived from a fatty acid (arachidonic acid) in cell membranes •

Other Lipids in the Body • Other fat-soluble vitamins • • Lipoproteins •

Proteins • • Joined by peptide bonds • Contain C, H, O, N, and sometimes S and P

Fibrous and Globular Proteins • Fibrous (structural) proteins • Strandlike, water insoluble, and stable • Examples:

Fibrous and Globular Proteins • Globular (functional) proteins • Compact, spherical, water-soluble and sensitive to environmental changes • Specific functional regions (active sites) • Examples:

Protein Denaturation • • Reversible in most cases, if normal conditions are restored • Irreversible if extreme changes damage the structure beyond repair (e.g., cooking an egg)

Enzymes • Biological catalysts • Lower the activation energy, increase the speed of a reaction (millions of reactions per minute!)

Characteristics of Enzymes • Often named for the reaction they catalyze; usually end in -ase (e.g., hydrolases, oxidases) • Some functional enzymes (holoenzymes) consist of: • Apoenzyme (protein) • Cofactor (metal ion) or coenzyme (a vitamin)

Nucleic Acids • DNA and RNA • • • Building block = nucleotide, composed of N-containing base, a pentose sugar, and a phosphate group

Deoxyribonucleic Acid (DNA) • Four bases: • • Double-stranded helical molecule in the cell nucleus • Provides instructions for protein synthesis • Replicates before cell division, ensuring genetic continuity

Ribonucleic Acid (RNA) • Four bases: • • Single-stranded molecule mostly active outside the nucleus • Three varieties of RNA carry out the DNA orders for protein synthesis •

Adenosine Triphosphate (ATP) •