Cell membrane overview and fluid mosaic model

Cell Membrane CH

Cell membrane

Protects cells from the harsh outside environment; vital for life.

The three main components of the cell membrane is:

• Phospholipids

• Cholesterol

• Proteins

Phospholipids

Make up the majority of the cell membrane, consisting of a polar head and two fatty acid tails.

Phospholipid Bilayer

Formed by phospholipids packed closely together. It looks like a cross-section when cut in half.

Cholesterol

Maintains the fluidity of the cell membrane by inserting itself between phospholipids and acting as like a buffer.

• Low Temp = Increased fluidity

• High Temp = Decreased fluidity

Integral proteins

Transmembrane proteins that cross the entire membrane.

Peripheral proteins

Proteins that sit on top of the membrane or another protein.

Rare Proteins

Can go halfway through the membrane or reside inside the bilayer between phospholipids.

Glycoproteins

Carbohydrates bound to proteins, playing a role in cell recognition.

Proteins that carry out the membrane process Include:

Receptors, Transporters, and light-bound proteins.

Receptors

Proteins act as communication channels, telling the cell what's going on outside.

Transporters

Transmembrane proteins help transport molecules in and out of the cell.

Lipid-bound proteins

Proteins stuck within the lipid bilayer are rare because they don't play a significant role in communication or transport.

Carbohydrates (Glyco-)

Bind to lipids or proteins, forming glycoproteins or glycolipids.

Carbohydrates (Glyco-) Function

They play a role in communication, allowing cells to recognize each other.

Carbohydrates (Glyco-) Location

Sugars mainly occur on the outside of the membrane, sticking out on proteins (glycoproteins) or lipids (glycolipids).

Fluid Mosaic Model

• You would see phospholipid head groups.

• Cholesterol would be interspersed.

• Larger proteins would be on top.

• Glycoproteins and glycolipids would be attached to proteins and phospholipids.

Fluidity

The components of the cell membrane (proteins and phospholipids) can move around.

• Discovered in 1972: The fluid mosaic model was discovered relatively recently.