Chapter 2: the Chemistry of life

biochemistry

study of molecules that compose living organisms

element

simplest form of matter to have unique chemical properties

atomic number

number of protons in the nucleus

trace elements

present in small amounts but play vital roles in the body

minerals

inorganic elements extracted from soil by plants, passed up the food chain to humans

protons

single positive charge mass= 1amu

Neutrons

no charge= 1amu

electrons

single negative charge, very low mass

valence electrons

in the outermost shell and determine the chemical bonding properties of an atom

isotopes

Varieties of an element differ only in the number of neutrons, therefore also in atomic mass

radioisotopes

unstable isotopes that decay and give off radiation in a process called radioactivity

radioactivity

process of isotopes decaying and giving off radiation

ionizing radiation

ejects electrons, destroys molecules, creates free radicals, and can cause mutations and cancer

physical half-life of radioisotopes

time required for 50% of unstable isotopes to decay to a stable state

biological half-life of radioisotopes

time required for 50% of unstable isotopes to disappear from the body

ion

charged particle with an unequal number of protons and electrons

Ionization

transfer of electrons from one atom to another

Anion

particle that has a net negative charge due to the gain of electrons

Cation

particle that has a net positive charge due to loss of electrons

salts

electrically neutral compounds of cations and anions; readily dissociate in water into ions and act as electrolytes

electrolytes

substances that ionize in water and form solutions capable of conducting electric current

free radicals

unstable highly reactive particles with an unusual number of electron

antioxidants

chemicals that neutralize free radicals

molecule

particle composed of two or more atoms united in chemical bond

compound

molecule composed of 2 or more different elements

molecular weight

sum of the atomic weights of its atoms

chemical bonds

hold atoms together withing a molecule or attract one molecule to another

ionic bonds

attraction of cation and anion

covalent bonds

Atoms share one or more pairs of electrons

single covalent bond

nuclei share 1 pair of electrons

double covalent bonds

nuclei share 2 pair of electrons

hydrogen bond

weak attraction between a slightly positive hydrogen atom in one molecule and a slightly negative oxygen or nitrogen atom in another atom

Van der Waals forces

weak, brief attractions between neutral atoms

mixture

consist of substances that are physically blended but not chemically combined; each substance retains its own chemical properties

solvency

ability to dissolve other chemicals

hydrophilic

substances dissolve in water

hydrophobic

substances that don’t dissolve in water

adhesion

tendency of one substance to cling to another

cohesion

tendency of molecules of the same substance to cling to each other

chemical reactivity

ability to participate in chemical reactions

solutions

consist of particles called solute mixed with a more abundant substance

Colloid

scatter light, cloudy, particles remain mixed when standing

suspensions

cloudy/opaque, separates on standing

emulsion

suspension of one liquid in another

acid

proton donor, releases H+ ions in water

base

proton acceptor, accepts H+ ions or releases OH- ions in water

buffers

chemical solutions that resist changes in pH

molarity

number of moles of solute per liter of solution

Milliequivalents per liter

expression of electrolyte concentration

energy

capacity to do work

potential energy

energy stored in an object that isn’t doing work currently

chemical energy

potential energy available in molecular bonds

free energy

potential energy available in a system to do work

kinetic energy

energy of motion, energy doing work

electromagnetic energy

kinetic energy of photons

chemical reaction

process in which a covalent or ionic bond is formed or broken

chemical equation

representation of a chemical reaction

decomposition reaction

large molecules break down into 2+ smaller ones

synthesis reaction

2+ small molecules combine into a larger one

exchange reaction

2 molecules exchange atoms or groups of atoms

reversible reaction

proceed in either direction under different circumstances

law of mass action

the direction of the reaction is based on the abundance of substances on either side of the equation

equilibrium

the ratio of products to reactants is stable

reaction rate can increase when

Concentration/temperature increases, or a catalyst is present

metabolism

all chemical reactions of the body

catabolism

Energy-releasing decomposition reactions, breaks covalent bonds, and produce smaller molecules.

anabolism

energy-storing synthesis reactions, requires energy input