CHEM Lecture 9

Question 1

what is a polar molecule

Answer 1

a molecule that forms favourable interactions with mater molecules - this includes molecules with polar bonds and molecules with charged regions - they are also called hydrophilic

Question 2

do alcohols ionise (dissociate)

Answer 2

never - they dissolve but never ionise - they are polar molecules

Question 3

what is a non-polar molecule

Answer 3

one which does not have any polar bonds or charged parts - also called hydrophobic

Question 4

do non-polar molecules dissolve in water

Answer 4

no but they dissolve in other non-polar solvents

Question 5

what is ionisation influenced by

Answer 5

the pH of the aqueous environment and
the prosperity of a particular ionisable functional group to ionise (fundamental physical property)

Question 6

when pKa = pH of the environment what percentage of the functional groups of the molecule are ionised

Answer 6

50%

Question 7

at less than 1 pH unit below the pKa are 90% of the molecules protonated or deprotonated

Answer 7

protonated

Question 8

at less than 1 pH unit above the pKa are 90% of the molecules protonated or deprotonated

Answer 8

deprotonated

Question 9

what does the net charge of a protein rely on

Answer 9

the ionisable side chains and the N and C termini (at the end of the chain) - the alpha amino and carboxyl groups are involved in bonds and not available for ionisation

Question 10

how are variations in the pH in aqueous environments minimised

Answer 10

using buffer

Question 11

in an aqueous environment what will water molecules try to do to non-polar molecules

Answer 11

to hydrate them by forming a constrained hydration shell around the molecule

Question 12

what do the non-polar lipid tails do in a biological membrane

Answer 12

constrain molecules to a particular location - inside or outside the cell (or organelle)