Lecture 7 - Membrane Structure Flashcards Preview

Unit 1 - Molecular and Cellular Principles of Medicine > Lecture 7 - Membrane Structure > Flashcards

Flashcards in Lecture 7 - Membrane Structure Deck (21):
1

What are the functions of biological membranes?

1. Selective permeability barrier

2. Comparmentalization of functions.

3. Identification

4. Signalling

5. Energy storage

2

What are common features of biological membranes? 

1. Sheetlike structures that can form closed boundaries in aqueous solution

2. Composed of lipid, protein, and carbohydrate

3. Lipid bilayer is relatively impermable to polar molecules

4. Membrane proteins carry out most specific fxns

5. Membranes are held together by non-covalent interactions

6. Biological membranes are asymmetric

7. Membranes are fluid under physiological conditions

3

Membrane lipids are .....

AMPHIPATHIC! - both hydrophobic (hydrocarbon tails) and hydrophilic (polar head groups)

4

Describe the structure of a phospholipid

5

Describe the effect of saturation and length of fatty acids chains

Increased saturation and increased length leads to decreased fluidity

6

What confirmation are naturally occuring unsaturated fatty acid chains in?

CIS

7

Describe the general structure of phospholipid backbone and give examples.

Glycerol or sphingosine (in sphingomyelin) - attach to fatty acids and phosphate via hydroxl groups

 

Glyercol attaches to 2 fatty chains, sphingosine carries on hydrocarbon of its own

8

What composes a phospholipid headgroups and give some examples

Phosphate + alcohol, ex. serine, choline, inositol, ethanolamine, etc.

9

What are other components of the membrane?

Glycolipids - sphingosine backbone w/ sugar attached

Cholesterol - makes membrane less flexible

10

Memorize the amphipathic properties of membrane lipids...

11

What are the forces at play in the spontaneous formation of lipid bilayers?

Hydrophobic effect, van der Waals, electrostatic and H bonding

12

What is the difference between transverse and lateral diffusion of membrane lipids

Transverse (flip flop) - very slow, protein mediated

Lateral - all the fucking time, gives fluidity

13

What are factors affecting fluidity?

1. Temp - needs to be above "melting temperature" to be fluid and free flowing

2. Length and degree of unsaturation of fatty acid chain - shorter, unsaturated = ^^ fluidity

3. Cholesterol content - decreases fluidity (lipid rafts)

14

What factors make a substance imperable to a lipid bilayer?

1. Polarity - ^ polarity means it won't get through

2. Size - the larger the molecule, the more difficult it will be to get through

15

How do drugs get into cells?

1. Passive diffusion

2. Hijacked transporters

3. Liposome delivery

4. Protein transduction

16

What is the relative ratio of lipid to proteins in the membrane?

Differs but around 1:1, there's more protein than people think

17

Types of membrane proteins...

Integral membrane proteins - transmembrane, monolayer associated, lipid linked - amphipathic to be inserted into membrane

Peripheral membrane proteins - protein attached

18

Fluid mosaic model

1. Lipid bilayer acts as solvent for membrane proteins

2. Membrane proteins are free to diffuse laterally, but cannot flip-flop

19

How can lateral diffusion of membrane proteins be constrained?

1. Anchoring protein to intracellular structure

2. Anchoring protein to extracellular structure

3. Protein/protein interactions b/n cells

4. Barriers by junction proteins

20

Describe lipid rafts

Regions of membrane that are more rigid and resistant to solubilization

Specific proteins are recruited for...

1. Signal transduction

2. Protein sorting

3. Recognition

4. Viral entry/exit

21

Describe some special properties of lipids in a membrane

Abnormal lipid distribution signal cells are dying