Physical Properties of Membrane

Question 0

Polar Heads & Fatty Acid Chain Tails

Answer 0

-Polar Head
>At least 6 different alcohol compounds linked to the C3 on the glycerol backbone
-Fatty Acid Chain
>Linked to C1 and C2 of the glycerol backbone
>14-24 carbons in length, and may be saturated or unsaturated

Question 1

Main. Chemical components of Membrane

Answer 1

• Amphipathic molecules
• Hydrophilic Polar Head group
• Glycerol backbone
• Hydrophobic fatty acid chain Tail

Question 2

Membrane Fluidity

Answer 2

Phospholipids can be organized in 2 different ways:

• Gel Phase: ordered, closely packed, tails fully extended, little movement
• Liquid Crystalline (fluid): low ordered, more random molecular motion.
• More space=More Motion

Question 3

Phase Transitions

Answer 3

• Induced by simply changing the temp.
• low temp=gel phase
• high temp=fluid phase
• Membrane can be Melted, loosens up with heat

Question 4

Differential Scanning Calorimetry

Answer 4

-Used to measure the “phase transition temp” (Tc)
>the temp at which lipids change phases
1. Hydrate lipids then heat w/ thermocouple to measure energy
2. The temp can be determined by the amount of energy given off

Question 5

Relation between Fatty Chain length and Tc

Answer 5

As chain length increases = transition temp increases

• More carbons require more energy to break chains
• Vanderwalls Interaction*

Question 6

Relation between Unsaturated tails and Tc

Answer 6

The presence of a double bound (unsaturated) Decreases the phase transition temp.
Cis-double bounds place Kinks (occupy much space) in the chain leading to a much drastically lower Tc than Trans-double bounds

Question 7

Relationship between Cholesterol and Tc

Answer 7

An Increase in Cholesterol = a Decrease in Tc

• No phase transition will occur if there is more than 50% Cholesterol.
• Cholesterol interferes with movement and prevents close packing within the bilayer
• This causes Gaps/Leaks in the membrane