C HAPTER 2 T HE C HEMISTRY OF L IFE

Section 2-1 Atom: Smallest unit of matter; can’t be broken down by chemical means. Atom has 3 particles: electrons (e-), protons (p+), neutrons (n). e- orbit nucleus in different energy levels p+ and n are in nucleus of the atom

Section 2-1 Element: Pure substance (sub) made of 1 kind of atom Elements differ in # of p+ their atoms contain # of n in atom is often but not always = to # of p+ in atom Oxygen atom

Section 2-1 Compound: sub made by joining atoms of 2 or more diff elements Atoms can join w/other atoms to form stable sub Force that joins atoms is called a chemical bond

Section 2-1 Covalent Bonds: Form when 2 or more atoms share e- Molecule: Group of atoms held together by covalent bonds.

Section 2-1 Hydrogen Bonds: In water, shared e- are attracted more strongly by O nucleus than by H nuclei Molecules w/unequal distribution of charge, such as water, are polar molecules Attraction between 2 water molecules is ex of hydrogen bond —weak chem attraction between polar molecules

Section 2-1 Ionic Bonds: Atom/molecule that gain/lose 1 or more e- is an ion Ions have electrical charge because they contain unequal # of e-/p+. Ions of opposite charge interact to form ionic bond

Section 2-2 Importance of Water to LT: Many organisms release excess heat through water evaporation This ability to control temp helps cells to maintain constant internal temp when external temp changes Water helps cells maintain homeostasis!

Section 2-2 Cohesion: Attraction between sub of the same kind Because of cohesion, water and other liquids form thin films/drops Molecules at surface of water are linked together by H bonds like a crowd of people linked by holding hands. This attraction between water molecules causes surface tension Surface tension

Section 2-2 Adhesion: Attraction between different substances Adhesion causes capillary action, in which water molecules move upward through narrow tube, such as stem of a plant

Section 2-2 Solution: Mixture of 1 or more substances evenly distributed in another substance Important substances in the body are dissolved in blood/other aqueous fluids Because these substances dissolve in water, they easily move w/in and between cells

Section 2-2 Polarity: Polarity of water enables many substances to dissolve in water When sodium chloride, NaCl, is dissolved in water, Na + and Cl – become surrounded by water molecules, H 2 O

Section 2-2 Nonpolar molecules: Nonpolar molecules don’t dissolve in water Inability of nonpolar molecules to dissolve in polar molecules is important to LT Shape/function of cell membrane depends on interaction of polar water w/ nonpolar membrane molecules Outside of cell Inside of cell

Section 2-2 Acids/Bases: Compds forming H+ when dissolved in water are acids Compds reduce[H+] in a sol’n are bases Many bases form hydroxide ions (OH-) when dissolved in water When acid is added to water, [H+] in sol’n is ↑ above that of pure water pH scale (0-14) measures [H+] Acids Bases

Section 2-3 Carbohydrates: Organic compounds made of C,H,O atoms in proportion of 1:2:1 Key source of energy; found in most foods— fruits, vegetables, grains

Section 2-3 Types of Carbohydrates: Building blocks of carbohydrates are single sugars, monosaccharides, glucose, C 6 H 12 O 6, and fructose Single sugars such as glucose are major source of energy in cell

Section 2-3 Disaccharides: Double sugar formed by 2 monosaccharides Sucrose, table sugar, consists of glucose and fructose.

Section 2-3 Polysaccharides: Starch are chains of 3 or more monosaccharides

Section 2-3 Lipids: Nonpolar molecules not soluble in water; fats, phospholipids, steroids, waxes Fats are lipids that store energy Typical fat has 3 fatty acids bonded to a glycerol molecule

Section 2-3 Saturated/Unsaturated Fats: Saturated fatty acid, all C atoms are bonded to 2 H atoms (except end C is bonded to 3 H atoms) Unsaturated fatty acid, some C atoms are linked by “double” covalent bond, each w/ only 1 H atom, producing kinks in molecule

Section 2-3 Proteins: Molecule formed by amino acids (aa) the building blocks of proteins 20 diff aa can form proteins

Section 2-3 Nucleic Acids: (DNA, RNA, ATP) Long chain of nucleotides w/ 3 parts: sugar, base, phosphate group DNA, deoxyribonucleic acid, 2 strands of nucleotides that spiral around each other RNA, ribonucleic acid, single strand

Section 2-3 ATP: Adenosine triphosphate, single nucleotide w/energy-storing phosphate gr When food molecules are broken down inside cells, some energy is stored as ATP ATP

Section 2-4 Energy: Ability to move/change matter Energy’s in many forms—light, heat, chemical, mechanical, electrical—can be converted from 1 form to another Energy can be stored/released by chem rxn

Section 2-4 Energy in Chemical Reactions Energy is absorbed/released when chemical bonds are broken and new ones formed Metabolism is used to describe all the chem rxn that occur w/in an organism Reactant = start with Product = end with

Section 2-4 Activation Energy (AE): Energy needed to start chemical rxn AE is a chem “push” that starts chem rxn Even in chem rxn that releases energy, AE must be supplied before rxn can occur

Section 2-4 Enzymes: Sub that speed up chemical rxn = catalyst and can lower AE of the rxn Enzymes are proteins that act on a specific substrate by attaching to the active sites of the substrate during a chemical rxn

Section 2-4 Enzymes: Example: amylase assists in the breakdown of starch to glucose (hydrolysis) Example: catalase assists in the breakdown of hydrogen peroxide to water and oxygen gas Enzymes in your body probably work best at 98° F or 37° C.

Section 2-4 Factors in Enzyme Activity: Factor that ∆ shape of enzyme can affect enzyme’s activity Temp/pH/shape of enzyme can alter enzymes effectiveness Enzymes that are active at any 1 time in a cell determine what happens in that cell