Biological Membranes: Structure, Lipids, and Fluidity

What are biological membranes primarily composed of?

Phospholipids

What are the two parts of a phospholipid?

A polar head and a non-polar tail

What does it mean for a phospholipid to be amphipathic?

It has both a polar head and a non-polar tail

How do lipid micelles form?

The hydrophilic heads interact with water while hydrophobic tails interact with one another.

What is a lipid bilayer?

A structure where hydrophilic heads interact with water and hydrophobic tails interact with each other.

What is a liposome?

A sphere composed of a lipid bilayer.

What allows liposomes and micelles to form stable configurations in water?

The hydrophilic heads interact with polar water molecules.

Name two types of proteins found in biological membranes.

Peripheral proteins and integral proteins.

What is the Sandwich Model of biological membranes?

An outdated model where proteins are on both surfaces (the bread) and lipids are in the middle (the meat).

What is the Fluid Mosaic Model?

A more accurate model where proteins are on both surfaces and some penetrate the membrane.

What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids have all single bonds; unsaturated fatty acids have double bonds between carbons.

How do saturated fatty acids affect membrane fluidity?

They decrease fluidity, making the membrane more solid.

How do unsaturated fatty acids affect membrane fluidity?

They increase fluidity, making the membrane more liquid.

What effect does hydrocarbon chain length have on lipid fluidity?

Longer chains decrease fluidity, while shorter chains increase fluidity.

What happens to membrane permeability as lipid fluidity increases?

Membrane permeability increases.

What causes a decrease in membrane fluidity?

Saturation of fatty acids and longer fatty acid chains.

What factors increase membrane fluidity?

Unsaturation of fatty acids and shorter fatty acid chains.

How does cholesterol affect membrane fluidity at high temperatures?

Cholesterol reduces fluidity and permeability.

How does cholesterol affect membrane fluidity at low temperatures?

Cholesterol increases fluidity and permeability.