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BIOL I > CHAPTER 2 > Flashcards

CHAPTER 2 Flashcards

1
Q

atoms

A

matter is composed of them; electrically neutral

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2
Q

electrons

A

negligible mass; negative charge

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3
Q

proton

A

have mass; positive charge (in nucleus)

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4
Q

neutrons

A

have mass; no charge (in nucleus)

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5
Q

dalton (Da)

A

mass of one proton or neutron; 1.7 x 10^-24 grams

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6
Q

element

A

fundamental substance containing only one kind of atom

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7
Q

atomic number

A

identifies an element; number of protons

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8
Q

mass number

A

protons + neutrons

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9
Q

isotopes

A

forms of an element with different numbers of neutrons, and thus different mass number
EXAMPLES: HYDROGEN (1 proton, 0 neutrons; DEUTERIUM 1 proton, 1 neutron; TRITIUM 1 proton, 2 neutrons)

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10
Q

radioisotopes

A

give off energy in the form of alpha, beta, and gamma radiation from nucleus (radioactive decay); atom is transformed, sometimes to a different element; can be incorporated into molecules as a tag or label

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11
Q

molecule

A

stable association of atoms

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12
Q

orbital

A

region where an electron is found at least 90% of the time

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13
Q

electron shells

A

sequence of orbitals; energy levels
FIRST - 1 orbital or 2 electrons
SECOND - 4 orbitals or 8 electrons
ADDITIONAL - 4 orbitals or 8 electrons
; the farther a shell from the nucleus, the higher energy level of electrons in that shell

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14
Q

valence shell

A

outermost electron shell; determines how the atom behaves; if full, atom is stable

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15
Q

octet rule

A

tendency of atoms to form stable molecules resulting in full valence shells

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16
Q

chemical bond

A

attractive force that links atoms together to form molecules

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17
Q

covalent bonds

A

atoms share one or more pairs of electrons so the outer shells are filled; each atom contributes one member of each electron pair; very strong; length, angle, and direction of bonds between any two elements are always the same; molecular shape can change as atoms rotate around a covalent bond

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18
Q

compound

A

pure substance made up of two or more different elements bonded together in a fixed ratio

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19
Q

molecular weight

A

sum of atomic weights of all atoms in the molecule

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20
Q

electronegativity

A

attractive force that an atomic nucleus exerts on electrons; depends on number of protons and distance between nucleus and electrons

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21
Q

nonpolar covalent bond

A

electrons are shared equally (atoms have similar electronegativity)

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22
Q

polar covalent bond

A

one atom has greater electronegativity, so electrons are drawn more to that nucleus

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23
Q

ionic bonds

A

complete transfer of electrons because of higher difference of electronegativity; two ions form with full outer shells

24
Q

ions

A

electrically charged particles formed when atoms lose or gain one or more electrons (CATIONS - positive; ANIONS - negative); can interact with polar molecules

25
Q

complex ions

A

groups of covalently bonded atoms that carry a charge (e.g. NH4+ and SO4-2)

26
Q

ionic bonds

A

formed by electrical attraction of positive and negative ions; in solids they are strong because ions are close together but in water they are far apart

27
Q

hydrogen bonds

A

attraction between the - end of one molecule and the + hydrogen end of another molecule; weaker than ionic and covalent bonds; many in a large molecule can be strong and play an important role in the structure of DNA and proteins

28
Q

hydrophilic

A

polar molecules that form hydrogen bonds with water

29
Q

hydrophobic

A

nonpolar molecules, such as hydrocarbons

30
Q

van der Waals forces

A

attraction between nonpolar molecules that are close together, brief and weak but can be substantial when summed over a large molecule; important when hydrophobic regions of molecules (enzyme and substrate) come together

31
Q

chemical reactions

A

occur when atoms collide with enough energy to combine or change their bonding patterns; matter and energy are neither created nor destroyed; therefore, they must be balanced

32
Q

oxidation-reduction (redox) reaction

A

electrons are transferred between two molecules (OXIDIZING AGENT - gains electrons; becomes reduced
REDUCING AGENT - loses electrons; becomes oxidized)

33
Q

energy

A

capacity to do work; capacity for change; changes form during chemical reactions

34
Q

Why does water have unusual properties?

A

polarity and ability to form hydrogen bonds

35
Q

Why does ice float?

A

each molecule of ice is hydrogen-bonded to four other molecules and the space between them make it less dense than water

36
Q

specific heat

A

amount of energy needed to raise the temperature of 1 gram of a substance by 1 degree Celsius; water has it high

37
Q

heat of vaporization

A

heat energy required to change liquid to gaseous state (evaporation); water has it high

38
Q

cohesion

A

hydrogen bonds between water molecules cause them to stick together; helps water move through plants; results in surface tension

39
Q

adhesion

A

attraction of water molecules to other molecules of a different type

40
Q

solution

A

substance (solute) dissolved in a liquid (solvent); dissolved molecules don’t lose their identity and properties; therefore, they can still react

41
Q

analyses

A

qualitative - identifying the substance
quantitative - measuring concentration or amount of substance

42
Q

mole

A

amount of a substance (in grams) numerically equal to its molecular weight (e.g. 1 mole of Na+ = 23 g)

43
Q

Avogadro’s number

A

number of molecules in 1 mole (6.02 x 10^23 molecules); constant

44
Q

molar (1 M) solution

A

1 mole / 1 liter

45
Q

acids

A

release hydrogen ions (H+) in water; if H+ concentration is increased, the solution is acidic; H+ ions can attach to other molecules and change their properties

46
Q

weak acids

A

not all the acid molecules dissociate into ions (e.g., acetic acid CH3COOH)

47
Q

strong acids

A

dissociate completely (e.g., hydrochloric acid HCl)

48
Q

bases

A

accept H+ ions

49
Q

strong base

A

NaOH

50
Q

weak base

A

bicarbonate ion (HCO3-), ammonia (NH3), and compounds with amino groups (NH2)

51
Q

acid-base reactions

A

may be reversible (ionization of strong acids and bases is irreversible; ionization of weak acids and bases is somewhat reversible)

52
Q

What is the connection with acids, bases, and water?

A

water acts as both a weak acid and weak base; has a slight tendency to ionize (important because of abundance of water in living systems and the reactive nature of H+ ions)

53
Q

pH

A

negative log of the molar concentration of free H+ ions in the solution, water = 7; the lower it is, the higher H+ concentration or greater acidity; influences rates of biological reactions; can change the 3-D structure of biological molecules which impacts function; organisms use many mechanisms to minimize its change in their cells and tissues

54
Q

buffer

A

weak acid and its corresponding base (e.g., carbonic acid (H2CO3) and bicarbonate ion (HCO3-)); help maintain constant pH; illustrate the law of mass action

55
Q

law of mass action

A

addition of a reactant on one side of a reversible system drives the system in the direction that uses up the compound; addition of an acid drives the reaction in one direction; addition of a base drives the reaction in the other direction

BIOL I (12 decks)

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