Chapter 2The Chemistry of Life

2-1 The Nature of MatterLiving things are made of chemical

compounds

Atom = the basic unit of matter

- made of protons (positive), electrons (negative), and neutrons (neutral)

- Atomic number = # of protons

- Atomic mass = protons plus neutrons

Element = a pure substance that consists of just one kind of atom

- Isotopes = atoms of the same element with different # of neutrons

- example: carbon 12, 13, 14

- Isotopes have the same # of electrons so they have the same chemical properties

- Radioactive Isotopes – Have unstable nuclei and break down at a constant rate over time… used to determine age of rocks and fossils, treat cancer, and kill bacteria

Compound = two or more elements bonded in definite proportions.

- example: H2O, NaCl

Chemical Bonds – involves valance electrons

- Ionic bond = one or more electrons are transferred from one atom to another, then opposite charges attract two ions

- Covalent bond = electrons are shared between atoms

- Molecule = when atoms are joined together by covalent bonds

- Van der Waals Forces = slight attraction between oppositely charged regions of nearby molecules

2-2 Properties of Water

Water is the single most abundant compound in most living things.

Properties

- Water expands as it freezes… ice floats on liquid water

- Polarity – oxygen atom attracts shared electrons stronger than the hydrogen atoms

- causes hydrogen bonds – attraction between slightly + and –

- cohesion = attraction between molecules of same substance; allows beading of water

and surface tension- adhesion = attraction between molecules of different substances; meniscus and

capillary action• Water properties website

Solutions and suspensions

- mixture = two or more elements physically mixed

- solution = mixture with evenly distributed molecules

- solute = dissolved substance

- solvent = substance in which solute is dissolved

- suspension = mixtures of water and nondissolved material

Acids, Bases and pH

- Water can split to form ions

H2O H+ + OH- the ions are

equal so water is neutral

- pH scale = indicates the concentration of hydrogen ions (H+)- acids = form H+ ions in water; pH value lower than 7- bases = form OH- ions in water; pH value higher than 7- buffers = weak acids or bases that can react with strong acids or bases to prevent changes in pH

2-3 Carbon Compounds

Carbon has four valence electrons and forms strong chains or rings

Macromolecules means “giant molecules”

- formed by a process of polymerization

- monomers = small units which are joined to form polymers

- Carbohydrates = main source of energy and used for structure

- made of carbon, hydrogen and oxygen, ratio 1:2:1

- monomers = sugars or monosaccharides; glucose

- polymers = starches or polysaccharides; glycogen, cellulose

Starch

Glucose

- Lipids = energy storage, insulation, makes up membranes- made of carbon, hydrogen and oxygen- examples: fats, oils, and waxes- saturated – no double bonds… butter- unsaturated – has double or triple bonds… olive oil- steroids – chemical messengers

- Nucleic acids = store and transmit hereditary information

- made of hydrogen, oxygen, carbon, and phosphorus

- monomers = nucleotides

- Proteins = control rate of chemical reactions, regulate cell processes, form bone and muscle, transport substances, fight diseases

- made of nitrogen, carbon, hydrogen, and oxygen

- monomers = amino acids; 20 different a.a. in nature

General structure Alanine Serine

Amino group Carboxyl group

Amino Acid Structure

Proteins form certain structures

Aminoacids

2-4 Chemical Reactions and Enzymes

Chemical reaction = process that changes, or transforms, one set of chemicals into another.

- Equation: reactants products

- Endothermic reaction = requires energy

- Exothermic reaction = releases energy; can occur spontaneously

- Activation energy = needed for most reactions to occur

Enzymes = proteins that act as biological catalysts, which speed up chemical reactions in the body… lowers activation energy

- usually specific to reaction and not used up in reaction

- Enzyme-substrate complex = site where reactants are brought together to react; fit like a lock and key

- Enzymes work in specific range of conditions: pH, temp