Cell Biology -- Ch2

Front 1

the properties of cells and their organelles derive directly from _________?

Back 1

the activities of the molecules of which they are composed

Front 2

covalent bond

Back 2

the type of chemical bond in which electron pairs are shared between two atoms
*joins together the atoms that make up molecules

Front 3

what governs the formation of covalent bonds

Back 3

atom is most stable when its outer most electron shell is filled

Front 4

what determines the number of covalent bonds possible

Back 4

the number of electrons needed to fill the outer shell

Front 5

octet rule

Back 5

the observation that when atoms bond, they often lose, gain, or share electrons to attain a filled outer shell of eight electrons

Front 6

how many covalent bonds can you have

Back 6

single - 1 pair electrons shared
double - 2 " " "
tripple - 3 " " "
*quadruple bonds are not known to occur

Front 7

when a covalent bond is formed, energy is ___

Back 7

released

Front 8

how much energy is needed to cleave C-H, C-C, or C-O covalent bonds

Back 8

1. relatively large
2. 80-100 kilocalories per mole
(kcal/mol)
3. these bonds stable under most conditions

Front 9

mole (mol)

Back 9

1. the SI base unit for the amount of a substance
2. the amount that contains a number of objects equal to the number of atoms in exactly 12g of carbon-12

Front 10

electrons are present around the nucleus in ___

Back 10

orbitals

Front 11

each orbital contains a maximum of ___ electrons

Back 11

2

Front 12

atoms with a similar number of outer shell electrons

Back 12

have similar properties

Front 13

example of a element with double covalent bond

Back 13

molecular oxygen (O2)

Front 14

example of element with tripple covalent bond

Back 14

molecular nitrogen (N2)

Front 15

give 2 examples that show how the type of bond between elements have important consequences in determining the shape of the molecule

Back 15

1. single bound elements are able to rotate relative to each other
2. double bound elements can function as energy capturing centers for respiration and photosynthesis

Front 16

what happens when two atoms of different elements bond to one another

Back 16

electrons are not shared equally

Front 17

electronegative atom

Back 17

1. the atom with the greater attractive force
2. the atom that can capture the major share of electrons of a covalent bond

Front 18

among biological molecules, which are strongly electronegative

Back 18

1. nitrogen
2. oxygen

Front 19

polar molecule

Back 19

molecules with an uneven distribution of charge because the component atoms have different electronegativities

Front 20

nonpolar molecule

Back 20

molecules with a symmetric distribution of charge because the component atoms have approximately the same electronegativities
*molecules that consist entirely of carbon & hydrogen atoms
**relatively inert

Front 21

list two biological molecules that exhibit both polar & nonpolar properties

Back 21

1. proteins
2. phoshpholipids

Front 22

ionic bond

Back 22

1. a noncovalent bond occuring between oppositely charged ions
2. also called a salt bridge

Front 23

ions

Back 23

an atom or molecule with a net positive or negative charge because it has lost or gained one or more electrons during a chemical reaction

Front 24

an anion with a negative charge is termed

Back 24

anion

Front 25

an anion with a positive charge is termed

Back 25

cation

Front 26

free radical

Back 26

highly reactive atom or molecule that contains a single unpaired electron

Front 27

what types of bonds govern interactions between molecules (or between different parts of a large biological molecule)

Back 27

a variety of linkages weaker than covalent -- noncovalent bonds

Front 28

noncovalent bond

Back 28

a relatively weak (1-5 kcal/mol) chemical bond based on attractive forces between oppositely charged regions within a molecule or between two nearby molecules

Front 29

what is the advantage of noncovalent bonds in a cell

Back 29

able to mediate the dynamic interactions among molecules in the cell

Front 30

T or F:
biomolecules are no different than chemistry molecules, and obey the same laws and rules

Back 30

T

Front 31

sterio-isomers

Back 31

two molecules that structurally are mirror images of each other and may have vastly different biological activity

Front 32

what is the #1 problem in chemical cell synthesis

Back 32

cells always produce the propper sterio-isomers; we do not

Front 33

which tend to attract reactions "farther out" --
covalent or ionic

Back 33

ionic

Front 34

compare reactions in vivo to those in vitro

Back 34

in vivo reactions are more efficient & selective (sterio-isomers) than in vitro

Front 35

where can ionic & hydrogen bonds be found relative to DNA

Back 35

1. ionic - protein (+ charged N atoms) bonds to DNA backbone (- charged O)
2. DNA molecule itself consists of two strands where base pairs held together by hydrogen bonds -- overall complex stable b/c so many H bonds

Front 36

list two ways free radicals are formed

Back 36

1. covalent bond is broken such that each portion keeps one half of the shared electrons
2. when an atom or molecule accepts a singel electron transfered during an oxidation reduction reaction

Front 37

T or F:
superoxide radicals are formed within the cells during normal oxidative metabolism

Back 37

T

Front 38

dismutase
[ex: superoxide dismutase (SOD)]

Back 38

generic name for enzymes catalyzing the reaction of two identical molecules to produce two molecules in differing states of oxidation or phosphorylation

Front 39

what 3 versions (isoforms) of SOD do animals possess

Back 39

1. cytosolic
2. mitochondrial
3. extracellular

Front 40

it is estimated that ___% of oxygen taken into the human mitochondria can be converted to hydrogen peroxide instead of water

Back 40

1-2%

Front 41

Harman's hypothesis

Back 41

hypothesis that free radicals can decrease life span

Front 42

how might reduced caloric intake increase longevity

Back 42

decreased caloric intake results in less O2- and H2O2 (free radicals)

Front 43

what are some common antioxidants found in the body

Back 43

1. glutathione
2. Vitamins E and C
3. beta carotene (orange pigment in carrots and other vegetables)
*studies do not indicate increase in longevity or decrease in aging process

Front 44

what is one antioxidant receiving considerable interest

Back 44

resveratrol, a polyphenolic compound found at high concentration in the skin of red grapes
*rather than scavenging for free radicals, seems to activate enzyme (Sir2) which is key player in promoting longevity

Front 45

are bonds between free ions a concern in the body? why(not)

Back 45

1. no
2. the + or - partial charges of water molecules surround the ion, keeping it from forming bonds with other molecules

Front 46

what is the strength of an ionic bond

Back 46

3 kcal/mol

Front 47

hydrogen bond

Back 47

the weak, attractive interaction between a hydrogen atom covalently bonded to an electronegative atom (thus, with a partial positive charge) and a second electronegative atom

Front 48

how strong is a hydrogen bond

Back 48

2-5 kcal/mol

Front 49

how does hydrogen bond strengh contribute to DNA construction and function

Back 49

1. the additive property of mutiple H bonds results in stable DNA structure (strong)
2. weakness of individual bonds allows DNA to be seperated whice enzymes access individual strands

Front 50

hydrophobic interaction

Back 50

the tendency of nonpolar molecules to aggregate so as to minimize their collective interaction with surrounding polar water molecules
*droplets of fat appearing in soup after you stir

Front 51

T or F hydrophobic reactions are considered true bonds

Back 51

F

Front 52

van der Waals force

Back 52

a weak attractive force due to transient asymmetries of charge within adjacent atoms or molecules
*electrons shared equally but not "exact"
*molecules need to be close and oriented properly

Front 53

how strong are van der Waals forces

Back 53

0.1-0.3 kcal/mol and very sensative to the distance between the atoms

Front 54

at what point do van der Waals attractions get stronger / weaker

Back 54

1. as atoms get close attraction increases up to about 4 A
2. if atoms approach closer their electron clouds will repel each other

Front 55

is there any scenarios where van der Waals interactions can form stronger bonds

Back 55

yes. large number of reactions can occur if the two molecules have complimentary surfaces

Front 56

discuss the length of hydrogen bonds as compared to covalent bonds

Back 56

hydrogen bonds are typically twice as long as the stronger covalent bonds