Molecular forces

Question 1

covalent bond

Answer 1

atoms share electrons

Question 2

non-covalent bond

Answer 2

different types of interactions lead to bond formation

Question 3

weakness of non-covalent bond

Answer 3

inheritance - DNA strands separate
compartment - bilayers etc
signalling - proteins and ligands

Question 4

ionic

Answer 4

for from permanent gain/ lose of e- forming permanent charge
e.g. Na+ and Cl-

Question 5

Quantitively description of ionic bond

Answer 5

E{coulomb} = q1q2 / kcr

Question 6

r

Answer 6

distance between q1 and q2 (charges)

Question 7

dipole interaction

Answer 7

have no net charge - partial charges such as water

Question 8

quanititive dipole interaction equation

Answer 8

E{dipole, charge} = q (vector) cos* / kcr(2)

Question 9

interaction energy between dipole and charge

Answer 9

falls with 1/r(2)

Question 10

dipole dipole equation

Answer 10

E{dip, dip} = (2(vector1 , vector2) / kcr(3)) f(angles)

Question 11

interaction energy between dipole and dipole

Answer 11

falls with 1/r(3)

Question 12

dispersion forces

Answer 12

neutral molecules with out partial charges can have temporary charges

Question 13

how dispersion forces are formed

Answer 13

by short lived uneven electron distribution

Question 14

induced induced equation

Answer 14

E{ind, ind} = -const / r(6)

Question 15

energy interaction between induced and induced

Answer 15

1/r(6)

Question 16

dispersion forces being universal

Answer 16

all molecules being attracted to each other

Question 17

Pauli exclusion principle

Answer 17

Quantum mechanics dictates no more than 2 electrons than occupy same orbital so can only get as close as electron distribution allows without overlapping

Question 18

VdW potential

Answer 18

where energy if minimal - specifies optimal distance between 2 atoms

Question 19

combining energy in VdW potential due to….

Answer 19

VdW radius with dispersion energy

Question 20

hydrogen bond requirements

Answer 20

2 electronegative atoms (N, O, F)

Question 21

H donor

Answer 21

H bond to electronegative

Question 22

H bond accepter

Answer 22

H can only bond with non-bonding pair of electrons on another electronegative atom

Question 23

examples in DNA

Answer 23

alpha helices - H bond between CO and NH

beta sheet - H bond between CO and NH - antiparallel strands - at angle (weaker)

Question 24

dipole-dipole attraction

Answer 24

dominating H bond interaction - electrostatic

Question 25

angular dependence

Answer 25

best of donor and acceptor in straight line - 180 degrees

Question 26

d{0} on graph

Answer 26

optimal distance

Question 27

How H bonds vary

Answer 27

dependent on donor and acceptor atoms

Question 28

Hydrophobic effect

Answer 28

non-polar molecules don’t mix well with polar molecules

Question 29

perturbation

Answer 29

effect increases as non-polar molecules affects polar solvent

Question 30

minimize free energy

Answer 30

more favourable when non-polar molecules cluster together

Question 31

non-polar molecules clustering

Answer 31

minimises perturbation of solvent

driven by maximizing entropy

Question 32

perturbation of polar solvent example

Answer 32

water - tetrahedron therefore has 6 options of H bond with neighbouring O atoms

Question 33

When adding hydrophobic group at the corner of tetrahedron

Answer 33

to decrease entropy of system

single C atom halves no. microstates

Question 34

packing together the hydrophobic group

Answer 34

causes less water perturbation

Question 35

hydrophobic effect driven

Answer 35

lipid assembly in to vesicles

bilayer sheets, liposome, micelle

Question 36

protein folding of hydrophobic effect

Answer 36

burying majority of amino acid with hydrophobic side chains in the core of protein