Phospholipid Layers

What are phospholipids?

Important structural components of cell membranes (bilayers)

What role does the phosphate group (PO4 3-) play in phospholipids?

It causes polarity in the molecule, creating a hydrophilic head and hydrophobic tails.

What is the arrangement of phospholipids in aqueous solutions?

Amphipathic molecules arrange themselves such that hydrophobic regions face away from water and hydrophilic face towards water to form hydrogen bonds

What is the structure of a phospholipid bilayer?

A double layer where hydrophobic fatty acid tails face each other to avoid water solutions inside and outside the cell

What does this double layer form?

The foundation of a plasma membrane

What does this double layer prevent the movement of?

Charged (hydrophilic) molecules and therefore are repelled

How do hydrophobic fatty acid tails interact with each other?

They are attracted to each other via weak forces of attraction.

What stabilizes the phospholipid bilayer?

The presence of cholesterol molecules interacting with phospholipids.

What do the phospholipid bilayer’s chemical properties allow?

Some molecules to easily pass

What do other molecules need?

A special type of transport system

Which types of molecules can easily pass through the phospholipid bilayer?

Hydrophobic (non-polar) molecules

Why can't hydrophilic (charged or polar) substances pass easily through the bilayer?

They are repelled by the hydrophobic interior of the phospholipid bilayer.

What are steroids and how do they interact with cell membranes?

A group of lipids with four fused rings of carbon atoms that are hydrophobic and can pass through cell membranes.

What is the function of steroids in the body?

They act as chemical messengers that are all hydrophobic