REDS :(

Question 1

What is potential energy?

Answer 1

Energy by virtue of position

Question 2

What is P (partition coefficient)

Answer 2

Its applied to solid equilibriums, used to work out gibbs at 0

Question 3

Define solution

Answer 3

Mixture of two or more components that form a single homogenous phase at the molecular level

Question 4

Steps of dissolution process

Answer 4

1. Drug molecule liberated from surface areas of particle
2. Drug concentrated in solution at surface
3. Solute migrates through boundary layer to bulk liquid by diffusion or convection
4. Local concentration of drug drops as it migrates from boundary layer

Question 5

Consequences of drug being too hydrophobic (too lipophilic) or hydrophilic

Answer 5

• If a compound is too lipophilic, it may be insoluble in aqueous media, it means it may bind too strongly to plasma proteins and therefore blood conc will be too low to have desired effect
• If its too polar it may not be absorbed through gut due to lack of membrane solubility
• SO its important lipophilicity of drug is known, we measure this using LogP

Question 6

Name some excipients used

Answer 6

Question 7

Name three different types of polyelectrolytes

Answer 7

• Polymers having ionisable functional groups
• Sometimes we might ionise it to for form this because it may have better properties e.g. soluble in water

Question 8

What is the isoelectric point (IEP)

Answer 8

IEP is the pH at which the effective net charge on a macromolecule is zero

Question 9

The different molecular structure/conformation of macromolecules in solution

Answer 9

Question 10

Define and the equation of Rheology

Answer 10

Rheology is the study of flow and deformation of properties of a matter

Question 11

Viscosity of a polymer in thermodynamically good solvent is LOWER OR HIGHER compared to the viscosity in thermodynamically poor solvent

Answer 11

HIGHER

Question 12

In relatively concentrated solutions the viscosity of polymers depends on the BLANK (non-Newtonian)

Answer 12

In relatively concentrated solutions the viscosity of polymers depends on the shear stress (non-Newtonian)

Question 13

Polymers can be precipitated from solutions upon addition of a BLANK

Answer 13

Polymers can be precipitated from solutions upon addition of a non-solvent

Question 14

In solutions macromolecules can change their conformations in response to the changes in BLANK

Answer 14

In solutions macromolecules can change their conformations in response to the changes in environmental conditions

Question 15

Three things to add to stabilise a suspension (pd or emulsion)

Answer 15

• ADD Electrolyte concentration - These create an electric double layer, leading to electrostatic repulsion between particles. This prevents particles from aggregating or settling
• ADD Surfactants: reduce interface tension between two phases - prevents seperation
• ADD hydrophilic polymer - cause steric hind, increase viscosity and wetting agents

Question 15

SUMMARY of both surfactant and solution factors effecting cmc important

Answer 15

Question 16

How is seperation of emulsions avoided

Answer 16

• Reduce droplet size
• Reduce concentration of dispersed phase
• Reduce density difference
• Increase viscosity of continuous phase

Question 17

What is a surfactant? Why does a surfactant lower surface tension?

Answer 17

• A surface-active agent lowers surface tension through adsorption at the interface
  such that its hydrophobic region is oriented towards the hydrophobic phase (air).
• The surfactant favours expansion of the interface and lowers surface tension by
  reducing the imbalance of surface forces.

Question 18

List THREE differences between chemisorption and physisorption. (3 marks)

Answer 18

• Chemisorption is a specific interaction where as physisorption is not
• Chemisorption is localised and physisorption mobile
• Chemisorption is non-reversible and physosorption due to weak interaction is reversible
• Chemisorption has maximum adsorption of a monolayer and physosorption processes can
  form multilayers
• Chemisorption processes are usually activated by increasing temperature

Question 19

A biological molecule is the active ingredient of a formulation and is found to adsorb strongly to the surface of a glass vial and this is shown to reduce the activity of the drug.
What TWO things could you look to change to alter, and potential reduce, the adsorption?

Answer 19

• You can alter the properties of the surface of the glass – make the glass surface more
  hydrophilic.
• Changing pH will change the surface activity of the biological molecule by changing the net charge.

Question 20

Answer 20