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CHAPTER 2 THE CHEMISTRY OF LIFE 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). p+ and n are in nucleus of the atom e- orbit nucleus in different energy levels 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 eMolecule: •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 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, H2O 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, C6H12O6, 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