Anatomy and Physiology Ch. 2: Chemistry Comes Alive

energy

the capacity to do work, or to put matter in motion

kinetic energy

energy in action

potential energy

stored energy; inactive energy that has the potential, or capability to do work but is not presently doing so

chemical energy

the form of energy stored in the bonds of chemical substances

electrical energy

results from the movement of charged particles

mechanical energy

energy directly involved in moving matter

radiant energy (electromagnetic energy)

energy that travels in waves

elements

unique substances that cannot be broken down into simpler substances by ordinary chemical methods; all matter is composed of elements

periodic table

a complete listing of the known elements; helps explain the properties of each element that make it react as it does with other elements

atoms

identical particles (building blocks) that make up elements

atomic symbol

a one- or two-letter chemical shorthand for each element

nucleus

the central part of an atom; contains protons and neutrons tightly bound together; nucleus is overall positively charged

protons

positive electrical charge; "heavy" particles with appx. the same mass as neutrons (1 amu)

neutrons

no electrical charge (neutral); "heavy" particles with appx. the same mass as protons (1 amu)

atomic mass unit (amu)

the mass of a proton and the mass of a neutron

electrons

tiny particles (0 amu) that have a negative charge that surround and orbit the nucleus

planetary model

a simplified (and now outdated) model of atomic structure; depicts electrons moving around the nucleus in fixed, generally circular orbits

orbitals

regions around the nucleus in which a given electron or electron pair is likely to be found most of the time

orbital model

modern model of atomic structure; more useful for predicting the chemical behavior of atoms

atomic number

the number of protons in an atom's nucleus

mass number

the sum of the masses of the protons and neutrons of an atom

isotopes

elements' two or more structural variations; have the same number of protons (and electrons), but a different number of neutrons

atomic weight

an average of the relative weights (mass numbers) of all the isotopes of an element, taking into account their relative abundance in nature

radioisotopes

isotopes that undergo the process of atomic decay (radioactivity); disintegration of a radioactive nucleus

molecule

two or more atoms held together by chemical bonds

compound

two or more different kinds of atoms bind to form a compound

mixtures

substances composed of two or more components physically intermixed

solutions

homogeneous mixtures of components that may be gases, liquids, or solids

solvent

the substance present in the greatest amount; the dissolving medium; usually liquids; water is the body's main solvent

solutes

substances present in smaller amounts

molarity

moles per liter; concentration of a solution; M

mole

an element or compound's atomic weight or molecular weight weighed out in grams

molecular weight

the sum of atomic weights of an element or compound

Avogadro's number

one mole of any substance always contains exactly the same number of solute particles; 6.02 X 10^23

colloids (emulsions)

heterogeneous mixtures; their composition is dissimilar in different areas of the mixture; appear translucent or milky

sol-gel transformations

to change reversibly from a fluid (sol) state to a more solid (gel) state (ex. Jell-O)

suspensions

heterogeneous mixtures with large, often visible solutes that tend to settle out (ex. sand & water)

chemical bonds

holds atoms together; an energy relationship between the electrons of the reacting atoms; made or broken in less than a trillionth of a second

electron shells

regions of space that consecutively surround the atomic nucleus; electrons forming the electron cloud around the nucleus of an atom

energy level

each electron shell represents a different energy level

valence shell

an atom's outermost energy level or the portion of it containing the electrons that are chemically reactive

octet rule (rule of eights)

except for shell 1, which is full when it has two electrons, atoms tend to interact in such a way that they have eight electrons in their valence shell

ions

charged particles

ionic bond

a chemical bond between atoms formed by the transfer of one or more electrons from one atom to the other

anion

atom that gains one or more electrons; electron acceptor; net negative charge

cation

atom that loses electrons; electron donor; net positive charge

crystals

large arrays of cations and anions held together by ionic bonds; salts

covalent bond

molecules that share electrons; shared electrons occupy a single orbital common to both atoms

nonpolar molecules

molecules that are electrically balanced; they do not have separate + and - poles of charge

polar molecules

molecules that have unequal electron pair sharing

electronegativity

atoms that are electron-hungry and attract electrons very strongly; small atoms with 6 or 7 valence shell electrons

electropositive

atoms with low electron-attracting ability; they lose their valence shell electrons; atoms with only one or two valence shell electrons

dipole

polar molecules (ex. water)

chemical reaction

whenever chemical bonds are formed, rearranged, or broken

hydrogen bonds

when a hydrogen atom, already covalently linked to one electronegative atom (usually nitrogen or oxygen), is attracted by another electron-hungry atom, so that a "bridge" forms between them

reactants

reacting substances in a chemical equation

products

produced substances in a chemical equation

molecular formula

formula for the products of an equation

synthesis (combination)

when atoms or molecules combine to form a larger, more complex molecule

anabolic

constructive activities in body cells

decomposition reaction

when a molecule is broken down into smaller molecules or its constituent atoms

catabolic

degradative processes in body cells; decomposition

exchange (displacement) reactions

chemical reactions involving body synthesis and decomposition

oxidation-reduction reactions (redox reactions)

decomposition reactions; the basis for all reactions in which food fuels are broken down for energy (where ATP is produced)

oxidized

reactant losing the electrons; electron donor

reduced

reacting taking up the transferred electrons; electron acceptor

exergonic reactions

reactions that release energy

endergonic reactions

reactions containing more potential energy in their chemical bonds than did the reactants

chemical equilibrium

for each molecule (AB) formed, one product molecule breaks down, releasing the reactants A and B; no further net charge

catalysts

substances that increase the rate of chemical reactions without themselves becoming chemically changed or part of the product

biochemistry

the study of the chemical composition and reactions of living matter

organic compounds

compounds that contain carbon

inorganic compounds

compounds that do not contain carbon; water, salts, and many acids and bases

universal solvent

water

hydration layers

water forms layers of water molecules around large charged molecules such as proteins, shielding them from the effects of other charged substances in the vicinity and preventing them from settling out of solution

hydrolysis reactions

decomposition reactions; substances are broken down into their building blocks by adding a water molecule to each bond to be broken

dehydration synthesis

when large carbohydrate or protein molecules are synthesized from smaller molecules, a water molecule is removed for every bond formed

salt

an ionic compound containing cations other than H+ and anions other than the hydroxyl ion (OH-); when salts are dissolved in water, they dissociate into their component ions

electrolytes

substances that conduct an electrical current in solution

acids

a substance that releases hydrogen ions (H+) in detectable amounts; proton donor; sour taste, can react with (dissolve) many metals, and burn a hole in your rug; when acids dissolve in water, they release hydrogen ions (protons) and anions

proton donors

because a hydrogen ion is just a hydrogen nucleus, or "naked" proton, acids are defined as proton donors; acids release an H+

bases

dissociate when dissolved in water and release hydroxyl ions (OH-) and cations; proton acceptors (take up H+ ions in detectable amounts; bitter taste, slippery feel

bicarbonate ion (HCO3-)

important base in the body; abundant in blood

ammonia (NH3)

base; a common waste product of protein breakdown in the body; one pair of unshared electrons that strongly attract protons

pH units

relative concentration of hydrogen ions in various body fluids; pH\=7 (neutral), pH\>7\=base, pH

neutralization reaction

when acids and bases are mixed, they react with each other in displacement reactions to form water and a salt

buffers

chemical systems (proteins and other types of molecules) in the kidneys and lungs that regulate the homeostasis of acid-base balance; resist abrupt and large swings in pH of body fluids by releasing hydrogen ions (acting as acids) when the pH begins to rise and by binding hydrogen ions (acting as bases) when the pH drops

strong acids

acids that dissociate completely and irreversibly in water

weak acids

acids that do not dissociate completely

strong bases

bases that dissociate easily in water and quickly tie up H+

weak bases

bases that accept relatively few protons

carbonic acid-bicarbonate system

the chemical equilibrium between carbonic acid (a weak acid) and bicarbonate ion (a weak base) resists changes in blood pH by shifting to the right or left as H+ ions are added to or removed from the blood

electroneutral

never loses of gains electrons (carbon)

polymers

chainlike molecules made of many similar or repeating units (monomers) which are joined together by dehydration synthesis; carbohydrates and proteins)

monomers

building blocks of polymers; joined together by covalent bonds

carbohydrates

a group of molecules that includes sugars and starches; represents 1-2% of cell mass; contain carbon, hydrogen, and oxygen; monosaccharides, disaccharides, polysaccharides, etc.

monosaccharide

simple sugars; single-chain or single-ring structures containing from three to seven carbon atoms

disaccharides

double sugar; formed when two monosaccharides are joined by dehydration synthesis (a water molecule is lost as the bond is made)

polysaccharides

polymers of simple sugars linked together by dehydration synthesis; their large size makes them good storage products

lipids

insoluble in water but dissolve readily in other lipids and in organic solvents such as alcohol and ether; contain carbon, hydrogen, oxygen, but proportion of oxygen in lipids is much lower; triglycerides