main chapter 2

chemical element

-simplest form of matter to have unique chemical properties; each element is identified by an atomic number (number of protons in an element's nucleus)-six most abundant: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus

trace elements

-required by an organism in only minute quantities-minerals: inorganic elements extracted from the soil by plants and passed up the food chain to humans and other organisms

atom

-smallest particle of an element-protons and neutrons are the nucleus-atomic mass is approximately equal to its total number of protons and neutrons-electrons are around the nucleus

protons

have a single positive charge; each weighs approximately 1 atomic mass unit

neutrons

have no charge; each weighs approximately 1 atomic mass unit

electrons

tiny particles with a single negative charge and very low mass; determine the chemical properties of an atom, governing what can exist and what chemical reactions can occur; \# of electrons \= \# of protons, so their charges cancel each other and an atom is electrically neutral

electron shells

-an energy level representing the distance of an electron from the nucleus of an atom; the more energy, the farther away from the nucleus-first shell holds maximum of two electrons-second and third shells hold maximum of eight electrons

valence electrons

electrons of the outermost shell; determine the chemical bonding properties of an atom

isotopes

atoms of the same element that have different numbers of neutrons; differ only in number of neutrons and therefore atomic mass

atomic weight

accounts for the fact that an element is a mixture of isotopes; the number of protons plus the number of neutrons

radioisotopes

unstable isotopes that break down into more stable isotopes

ionizing radiation

-high-energy radiation ejects electrons from atoms, converting atoms to ions; quickly fatal in high doses; mutagenic or carcinogenic in low doses (ex. ultraviolet rays and x-rays)-alpha particles, beta particles, and gamma rays

alpha particle

consists of two protons and two neutrons; too large to penetrate the skin

beta particle

free electron; penetrate only a few millimeters of the skin

physical half-life

time required for 50% of a radioisotope's atoms to decay to a more stable state

biological half-life

time required for half of a radioisotope to disappear from the body

ions

charged particles with unequal numbers of protons and electrons; opposite charges attract; form because elements with 1-3 valence electrons tend to give them up and those with 4-7 electrons tend to gain more

ionization

the process by which neutral molecules gain or lose electrons

anion

particle that gains electrons acquires a negative charge

cation

particle that loses electrons acquires a positive charge (because it then has a surplus of protons)

valence

charge on an ion

electrolytes

release ions into solution when broken down; substances that ionize water and form solutions capable of conducting electricity; important for their chemical reactivity (as when calcium phosphate becomes incorporated into bone) and electrical effects (essential to nerve and muscle function)

free radicals

chemical particles with an odd number of electrons; produced by some normal metabolic reactions of the body (ATP), radiation (UV light), and by chemicals (nitrates); short-lived and combine quickly with molecules; damaged caused by them is cancer

antioxidant

chemical that neutralizes free radicals; produces superoxide dismutase

molecules

chemical particles composed of two or more atoms united by a chemical bond

compounds

two or more elements chemically combined (ex. CO2)

isomers

compounds with the same formula but different structural arrangements

molecular weight

sum of the atomic weights of a compound's atoms

chemical bonds

the attractive forces that hold atoms together

ionic bonds

attraction of a cation to an anion; relatively weak attraction between and ion and a cation (ex. NaCl)

covalent bonds

form by the sharing of electrons

single covalent bond

sharing of a single pair of electrons (ex. H--H)

double covalent bond

sharing of two pairs of electrons (ex. O\=C\=O)

nonpolar covalent bond

covalent bond where electrons are shared equally

polar covalent bond

covalent bond between atoms in which the electrons are shared unequally

hydrogen bond

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

van der Waals forces

slight attraction that develops between oppositely charged regions of nearby molecules; if the electrons briefly crowd toward one side of an atom, they render that side slightly negative and the other side slightly positive for a moment; if another atom is close enough to this one, the second atom responds with disturbances in its own electron cloud

mixture

consists of substances that are physically blended but not chemically combined

water

constitutes 50% to 75% of your body weight; solvency, cohesion, adhesion, chemical reactivity, and thermal stability; universal solvent because it dissolves a broader range of substances than any other liquid; cohesive liquid because of hydrogen bonds

solvency

ability to dissolve other chemicals

hydrophilic

substances that dissolve in water (ex. sugar)

hydrophobic

substances that do not dissolve in water (ex. fats)

adhesion

tendency of one substance to cling to another

cohesion

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

chemical relativity

water's ability to participate in chemical reactions; water ionizes H+ and OH-; these ions can be incorporated into other other molecules, or released from them, in the course of chemical reactions such as hydrolysis and dehydration synthesis

thermal stability

helps to stabilize the internal temperature of the body; results from the high heat capacity of water - the amount of heat that raises the temperature of 1 g of a substance by 1 degree C

calorie

amount of energy needed to raise temperature 1 gram of water 1 degree C

solution

consists of particles of matter called solute mixed with a more abundant substance called the solvent; can be a gas, solid, or liquid

\-particles are under 1 nanometer (nm) in size; solute and solvent cannot be visually distinguished from each other

\-such small particles do not scatter light noticeably, so they're usually transparent

\-solute particles will pass through most selectively permeable membranes

\-solute doesn't separate from the solvent when the solution is allowed to stand

emulsion

particles that are intermediate in size between those in solutions and suspensions form mixtures

\-particles range from 1 to 100 nm in size

\-particles this large scatter light, so they're usually cloudy

\-particles are too large to pass through most selectively permeable membranes

\-particles are still small enough to remain permanently mixed with the solvent when the mixture stands

any mixture of two or more immiscible liquids in which one liquid is dispersed in the other

suspension

blood cells in our plasma

\-particles exceed 100 nm in size

\-such large particles render suspensions cloudy or opaque

\-particles are too large to penetrate selectively permeable membranes

\-particles are too heavy to remain permanently suspended, so suspensions separate onto standing

a mixture in which particles can be seen and easily separated by settling or filtration

acid

releases hydrogen ions into solutions; a proton donor, a molecule that releases a proton (H+) in water; pH below 7 (ex. HCl)

base

proton acceptor; release hydroxide ions into solutions; does not have to be a hydroxide donor; pH above 7 (ex. NaOH)

pH

how acidity is expressed; a measure derived from the molarity of H+

neutral

solution with a pH of 7

buffers

chemical solutions that resist changes in pH; release hydrogen ions if pH rising is too high

molarity

M; one mole of a chemical is the number of grams equal to its molecular weight; measure of the number of moles of solute per liter of solution; number of molecules determines the physiological effect of a solution

energy

capacity to do work

work

to move something

potential energy

energy contained in an object because of its position or internal state but that is not doing work at the time

kinetic energy

energy of motion; energy that is doing work

chemical energy

potential energy stored in bonds of molecules; chemical reactions release this energy and make it available for physiological work

heat

kinetic energy of molecular motion; adding this to a substance increased molecular motion

electromagnetic energy

kinetic energy of moving "packets" of radiation called photons

electrical energy

has both potential and kinetic forms; when charged particles have accumulated at a point, it is potential; when these particles begin to move and create an electrical current, it is kinetic

free energy

potential energy available in a system to do useful work

chemical reaction

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

factors that determine: temperature (reaction rate increases as the temperature rises because heat causes molecules to move more rapidly and collide with greater force and frequency), concentration (reaction rate increases when reactants are more concentrated because the molecules are more crowded and collide more frequently), catalysts, particle size (smaller particles, quicker they move)

decomposition reaction

large molecule breaks down into two or more smaller ones (ex. AB -\> A + B)

synthesis reaction

two or more small molecules combine to form a larger one (ex. A + B -\> AB)

exchange reaction

two molecules exchange atoms or groups of atoms (ex. AB + CD -\> AC + BD)

reversible reaction

can go in either direction under different circumstances; direction to which it goes is determined by the relative abundance of substances on each side of the equation; follow the law of mass action; exist in a state of equilibrium

law of mass action

they proceed from the reactants in greater quantity to the substances with the lesser quantity

equilibrium

ratio of products to reactants is stable

catalysts

substances that temporarily bind to reactants, hold them in favorable position to react with each other, and may change the shapes of reactants in ways that make them more likely to react

metabolism

all the chemical reactions in the body; divisions: catabolism and anabolism

catabolism

metabolic pathways that break down molecules, releasing energy; exergonic reactions (reactions that release energy)

anabolism

metabolic pathways that construct molecules, requiring energy; endergonic reactions (reactions that absorb energy)

oxidation

any chemical reaction in which a molecule gives up electrons and releases energy; oxidizing agent (electron acceptor)

reduction

chemical reaction in which a molecule gains electrons and energy; reducing agent (electron donor)

oxidation-reduction reactions

oxidation of one molecule is always accompanied by the reduction of another

carbon backbones

carry a variety of functional groups

functional groups

small clusters of atoms that determine many of the properties of an organic molecule (ex. carboxyl group, phosphate groups, hydroxyl group, methyl group, amino group)

hydroxyl structure

occurs in sugars and alcohols (-OH)

methyl structure

occurs in fats, oils, steroids, and amino acids (-CH3)

carboxyl structure

occurs in amino acids, sugars, and proteins (-COOH)

amino structure

occurs in amino acids and proteins (-NH2)

phosphate structure

occurs in nucleic acids and ATP (-H2PO4)

polymers

molecules made of a repetitive series of identical or similar subunits called monomers (ex. starch)

monomers

small unit that can join together with other small units to form polymers

polymerization

the joining of monomers to form a polymer

dehydration synthesis

condensation; a chemical reaction in which two molecules are bonded together with the removal of a water molecule; creates disaccharides

hydrolysis

reaction where water split into two hydrogens and one oxygen; this breaks a polymer; breaks down disaccharides

carbohydrates

\-sugars

\-provide energy for cells \n -supplies materials for building cells \n -acts as store energy reserves within chemical bonds \n -composed of carbon, hydrogen, and oxygen (carbon hydrogen typically in 1:2:1 ratio) \n -more simple carbohydrates are water soluble \n -building blocks: monosaccharides (glucose, galactose, fructose), disaccharides (sucrose, lactose, maltose), polysaccharides (cellulose, starch, glycogen), conjugated carbohydrates (glycoprotein, glycolipid, proteoglycan)

monosaccharides

simple sugars (glucose, galactose, and fructose)

disaccharides

sugars composed of two monosaccharides (sucrose, lactose, maltose)

glucose

C6H12O6; a simple sugar that is an important source of energy; blood sugar

galactose

converted to glucose and metabolized

fructose

fruit sugar; converted to glucose and metabolized

sucrose

(glucose + fructose) produced by sugar cane and sugar beets

maltose

(glucose + glucose) product of starch digestion; malt sugar; further digested into glucose

lactose

(glucose + galactose) milk sugar; important in infant nutrition