Lecture 2: Molecular Interactions

Question 1

biomolecules are mostly stable because of __

Answer 1

strong covalent bonds

Question 2

the structure and function of the cell itself are stabilized by

Answer 2

weak interactions

Question 3

what are the 5 types of molecular interactions?

Answer 3

1. covalent bonds
2. ionic bonds
3. hydrogen bonds
4. Van der Waals
5. hydrophobic effects

Question 4

what are chemical bonds?

Answer 4

forces that hold atoms together to make molecules

Question 5

what is the basic reason for chemicals reacting with each other?

Answer 5

to get a full octet (noble gas configuration) to be more stable

Question 6

electron __ or __ results in a chemical bond

Answer 6

sharing ; transfer

Question 7

sharing electrons results in __ bonds

Answer 7

covalent

Question 8

covalent bonds only occur when

Answer 8

ionic bonds are highly unfavourable

Question 9

ionic and covalent bonds are extremes along a __ of electron sharing

Answer 9

continuum

Question 10

covalent bonds in which there is uneven sharing is called __

Answer 10

polar

Question 11

electronegativity

Answer 11

propensity to attract electrons

Question 12

in covalent bonds, electrons are __ and orbitals __

Answer 12

shared ; overlapped

Question 13

which is stronger: covalent or ionic bonds

Answer 13

covalent

Question 14

which elements are more likely to engage in covalent bonding ?

Answer 14

non-metals (Including CHNOPS)

Question 15

bond strength is equal to

Answer 15

amount of energy needed to break the bonds

Question 16

what are ionic bonds?

Answer 16

interactions between distinct electrical charges on atoms

Question 17

ionic interactions play a role in biochemical functions, such as ___ and __

Answer 17

enzymatic reactions; RNA< DNA and protein synthesis

Question 18

ionic bonds only form when an element is able to ___

Answer 18

lose one or 2 electrons and the other can accept them

Question 19

carbon would need to lose or gain __ electrons to engage in ionic interactions

Answer 19

4

Question 20

na and cl are held together by ___ interactions in a __ array

Answer 20

charge-charge; crystalline

Question 21

water molecules dissolve ions, which ___ the bonds and ___ the charges

Answer 21

destroys; shields

Question 22

individual ions bind to water molecules through a __ interaction

Answer 22

charge – dipole

Question 23

charge – dipole interaction is a chemical bond (T/F)

Answer 23

false

Question 24

a charge – dipole interaction occurs between a ___ and __

Answer 24

dipole; charged atom or molecule

Question 25

a molecule with partial separation is called a __

Answer 25

dipole

Question 26

a dipole is the result of ___ sharing

Answer 26

unequal

Question 27

what are van der waals interactions?

Answer 27

relatively weak electrostatic interactions between 2 neutral groups with a dipole

Question 28

do van der waals only occur between molecules with a permanent dipole? why/ why not?

Answer 28

no, because of random fluctuations in distributions of electrons

Question 29

dipole – dipole

Answer 29

between molecules with permanent dipoles

Question 30

dipole – induced dipole

Answer 30

permanent dipole in one causes a dipole in another

Question 31

induced dipole – induced dipole

Answer 31

random fluctuations in electrons in one molecule sets up a temporary dipole that induces a dipole in another

Question 32

which interaction is very weak, but contributes to cohesiveness?

Answer 32

induced dipole – induced dipole

Question 33

induced dipole – induced dipole are also called

Answer 33

London forces

Question 34

a dipole can be induced in aromatic / resonance structures (T/F)

Answer 34

true

Question 35

fluctuating electron density allows for ___ to occur

Answer 35

transient dipoles

Question 36

maximum interaction occurs when groups are separated by a ___ distance called the ___

Answer 36

precise; van der waals distance

Question 37

what happens to the interaction if the groups are too far apart?

Answer 37

no interaction

Question 38

what happens to the interaction if the groups are too close together?

Answer 38

repulsion takes over

Question 39

van der waals interactions are important to the ___ of all large molecules, like __ and __

Answer 39

structure; DNA, proteins

Question 40

what interactions stabilize the DNA double helix?

Answer 40

1. van der waal interactions between stacked bases
2. hydrophobic effect
3. hydrogen bonds between base pairs

Question 41

hydrogen bonds are a type of ___ interactions

Answer 41

dipole – dipole van der waals

Question 42

a hydrogen bond can happen anytime an H is bound to a ___ atom, such as ___

Answer 42

very electronegative; O, N, F, sometimes S

Question 43

a hydrogen bond involves some level of electron __, therefore a ___ bond

Answer 43

sharing; covalent

Question 44

the distance between atoms in a hydrogen bond is ___ than in normal van der waals

Answer 44

shorter

Question 45

bond strength is ___ in hydrogen bonds than in typical covalent bonds

Answer 45

higher/stronger

Question 46

hydrogen bonds are strong enough to ___, but weak enough to ___

Answer 46

be a stable interaction; break if needed

Question 47

the alpha helix is maintained by ___ bonds between groups in the protein chain

Answer 47

hydrogen

Question 48

hydrophobic interactions occur between molecules that cannot interact with ___

Answer 48

water

Question 49

what is the weakest type of noncovalent bonds?

Answer 49

hydrophobic effects

Question 50

hydrophobic effects are able to break and reform, giving them a __

Answer 50

dynamic flexibility

Question 51

noncovalent bonds can sum to provide ___

Answer 51

more stability