CHAPTER 2THE 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).

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 2-1Compound: 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 2-1Covalent Bonds:

•Form when 2 or more atoms share e-

Molecule: •Group of atoms held together by covalent bonds.

Section 2-1Hydrogen 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 2-1Ionic 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 2-2Importance 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 2-2Cohesion:

•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 tensionSurface tension Surface tension

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

Section 2-2Solution:

•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 2-2Polarity:

•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 2-2Nonpolar molecules:

•Nonpolar molecules don’t dissolve in waterInability 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 2-2Acids/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 2-3Carbohydrates:

•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 2-3Types 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 2-3Disaccharides:

•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 2-3Lipids:

•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 2-3Saturated/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 2-3Proteins:

•Molecule formed by amino acids (aa) the building blocks of proteins•20 diff aa can form proteins

Section 2-3Nucleic 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 2-3ATP:

•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 2-4Energy 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 withProduct = end with

Section 2-4Activation 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 2-4Enzymes:

•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 2-4Enzymes:

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 2-4Factors 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