Lecture 2: Molecular Interactions Flashcards
biomolecules are mostly stable because of __
strong covalent bonds
the structure and function of the cell itself are stabilized by
weak interactions
what are the 5 types of molecular interactions?
- covalent bonds
- ionic bonds
- hydrogen bonds
- Van der Waals
- hydrophobic effects
what are chemical bonds?
forces that hold atoms together to make molecules
what is the basic reason for chemicals reacting with each other?
to get a full octet (noble gas configuration) to be more stable
electron __ or __ results in a chemical bond
sharing ; transfer
sharing electrons results in __ bonds
covalent
covalent bonds only occur when
ionic bonds are highly unfavourable
ionic and covalent bonds are extremes along a __ of electron sharing
continuum
covalent bonds in which there is uneven sharing is called __
polar
electronegativity
propensity to attract electrons
in covalent bonds, electrons are __ and orbitals __
shared ; overlapped
which is stronger: covalent or ionic bonds
covalent
which elements are more likely to engage in covalent bonding ?
non-metals (Including CHNOPS)
bond strength is equal to
amount of energy needed to break the bonds
what are ionic bonds?
interactions between distinct electrical charges on atoms
ionic interactions play a role in biochemical functions, such as ___ and __
enzymatic reactions; RNA< DNA and protein synthesis
ionic bonds only form when an element is able to ___
lose one or 2 electrons and the other can accept them
carbon would need to lose or gain __ electrons to engage in ionic interactions
4
na and cl are held together by ___ interactions in a __ array
charge-charge; crystalline
water molecules dissolve ions, which ___ the bonds and ___ the charges
destroys; shields
individual ions bind to water molecules through a __ interaction
charge – dipole
charge – dipole interaction is a chemical bond (T/F)
false
a charge – dipole interaction occurs between a ___ and __
dipole; charged atom or molecule
a molecule with partial separation is called a __
dipole
a dipole is the result of ___ sharing
unequal
what are van der waals interactions?
relatively weak electrostatic interactions between 2 neutral groups with a dipole
do van der waals only occur between molecules with a permanent dipole? why/ why not?
no, because of random fluctuations in distributions of electrons
dipole – dipole
between molecules with permanent dipoles
dipole – induced dipole
permanent dipole in one causes a dipole in another
induced dipole – induced dipole
random fluctuations in electrons in one molecule sets up a temporary dipole that induces a dipole in another
which interaction is very weak, but contributes to cohesiveness?
induced dipole – induced dipole
induced dipole – induced dipole are also called
London forces
a dipole can be induced in aromatic / resonance structures (T/F)
true
fluctuating electron density allows for ___ to occur
transient dipoles
maximum interaction occurs when groups are separated by a ___ distance called the ___
precise; van der waals distance
what happens to the interaction if the groups are too far apart?
no interaction
what happens to the interaction if the groups are too close together?
repulsion takes over
van der waals interactions are important to the ___ of all large molecules, like __ and __
structure; DNA, proteins
what interactions stabilize the DNA double helix?
- van der waal interactions between stacked bases
- hydrophobic effect
- hydrogen bonds between base pairs
hydrogen bonds are a type of ___ interactions
dipole – dipole van der waals
a hydrogen bond can happen anytime an H is bound to a ___ atom, such as ___
very electronegative; O, N, F, sometimes S
a hydrogen bond involves some level of electron __, therefore a ___ bond
sharing; covalent
the distance between atoms in a hydrogen bond is ___ than in normal van der waals
shorter
bond strength is ___ in hydrogen bonds than in typical covalent bonds
higher/stronger
hydrogen bonds are strong enough to ___, but weak enough to ___
be a stable interaction; break if needed
the alpha helix is maintained by ___ bonds between groups in the protein chain
hydrogen
hydrophobic interactions occur between molecules that cannot interact with ___
water
what is the weakest type of noncovalent bonds?
hydrophobic effects
hydrophobic effects are able to break and reform, giving them a __
dynamic flexibility
noncovalent bonds can sum to provide ___
more stability
