Surfactants and micelles Flashcards Preview

Pharmacy (year one) > Surfactants and micelles > Flashcards

Flashcards in Surfactants and micelles Deck (26)
Loading flashcards...
1
Q

The double affinity of amphipathic molecules makes them migrate towards the _________ to minimise energy. As a result they _________ surface tension

A

surface - to reduce hydrophobic region contact with water

reduce

2
Q

Proteins, peptides, polymers, phospholipids and surfactants are examples of _________

A

amphipathic molecules

3
Q

What are surfactants?

A

Amphipathic molecules exhibiting a surface tension property (reduce)

4
Q

What are the 4 categories that surfactants can be divided into?

A

Anionic
Non-ionic
Zwitterionic
Cationic

5
Q

What are two examples of anionic surfactants?

A
Sodium dodecanoate
Sodium dodecyl (lauryl) sulfate
6
Q

What are anionic surfactants usually combined with?

A

alkaline metal or a quaternary ammonium

7
Q

Why are charged surfactants not usually used in oral formulations?

A

Because they are toxic

8
Q

Why don’t non ionic surfactants ionise in solution?

A

Hydrophilic group is non dissociable at physiological pHs

9
Q

Tween 20 and tween 80 are examples of what type of surfactant?

A

Non ionic

10
Q

Which type of surfactant is found in injections and oral formulations?

A

Non ionic

11
Q

Which type of surfactant is mostly combined with halogen type anions?

A

Cationic

12
Q

Which type of surfactant is used as bactericides?

A

Cationic - positive charge binds to the negative surface of cells

13
Q

Cetrimide (CTAB) is an example of which type of surfactant?

A

Cationic

14
Q

Betaines, sulfobetaines and natural substances such as amino acids are examples of which type of surfactant?

A

Cationic

15
Q

What happens above cmc (critical micelle concentration)?

A

Any further addition of surfactant above cmc results in the formation of micelles

16
Q

The ability of reducing ________ depends on surfactant structure (length/size of hydrophobic/hydrophilic parts)

A

surface tension

17
Q

The ability of a surfactant to reduce surface tension is independent of the balance between hydrophobic and hydrophilic properties (HLB). True or false?

A

False - it does depend

18
Q

An increase in the length of hydrocarbon chain results in a decrease in surface tension reduction. True or false?

A

False - results in an increased surface tension reduction (Traube’s rule)

19
Q

When are micelles formed?

A

Above cmc

20
Q

Can dilution result in the disappearance of micelles?

A

Yes

21
Q

What is the difference between micelles and inverted micelles?

A

In micelles the hydrophilic head is in contact with the polar solvent and the hydrophobic tail inside.
In inverted micelles, the hydrophobic tail is in contact with the organic solvent (oil) and hydrophilic head inside

22
Q

What is solubilisation?

A

When a water insoluble substance is brought into solution by incorporation in micelles. The incorporated substance is called the solubilisate

23
Q

Where in a micelle will molecules with a high logP be positioned?

A

inside the micelle

24
Q

Non-polar solubilisates are dissolved in the core of a micelle. True or false?

A

True

25
Q

What are the pharmaceutical applications of surfactants?

A
Enhancers for percutaneous absorption
Flocculating agents for suspensions
Mouthwashes 
Respiratory distress therapy 
Suppositories
Suspension aerosols 
Water based aerosols 
Contact lens cleansing agents
Hard gelatin capsules
Emulsifiers 
Cerumen removing solutions (ear drops)
26
Q

What are liposomes and what are they used for?

A

Made of phospholipids/surfactants. They are used as controlled release drug delivery systems, in particular in cancer chemotherapy due to EPR

Decks in Pharmacy (year one) Class (60):