IV.1 Lipids + IV.2 Membrane structure and function

7 important questions on IV.1 Lipids + IV.2 Membrane structure and function

What are the physical features of lipids?

Lipids have a hydrophilic head and two hydrophobic tails.

What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids are ‘full’, you can’t do anything with them
Unsaturated fatty acids are ‘hungry’, they usually have a double bond which can be broken to add atoms.
The difference in lipids is that saturated fatty acids have a low fluidity, unsaturated fatty acids are less densely packed so a higher fluidity.

How does lipid composition influence membrane features?

When a membrane is closely packed there is less fluidity, when it is less dense there is more fluidity. This can be achieved by changes in temperature and the type of lipid (saturated/unsaturated).
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How are lipid membranes formed and help together?

Formed: first a micelle is formed (lipid headgroups facing towards the water phase), growing and flattening a micelle will result in a lipid bilayer. A sheet is energetically unfavorable (edges are exposed to water) so a sealed compartment is then formed.
Held together: electrostatic interactions of headgroups with water (hydrogen bonds) and ions (salt bridges) and the hydrophobic effect of fatty acids.

What is the biological function of membranes?

A membrane is a selective permeability barrier.

What are lipid rafts?

A lipid raft contains more lipids than usual, therefore it is less fluid, which means less movement, so the membrane is more rigid (=stijf).

What is the role of a flippase and why is it important?

In order to achieve asymmetry (incorporation of lipids into the outer layer) and growth (incorporation of different lipids in the outer layer) in general, the enzyme fippase allows lipids to flip across the membrane.

The question on the page originate from the summary of the following study material:

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