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Describe the Plasma (cell) membrane

It surrounds the cell.

Made of proteins and lipids.

Composition and function can vary from one region of the cell to another.


What is the Unit Membrane?

Forms the border of the cell and many of its organelles.

Appears as a pair of dark parallel lines around the cell (when viewed with an electron microscope)


What is the function of the plasma membrane?

-Unit membrane at the cell surface.
- Defines cell boundaries
-Governs interactions with other cells.
-Controls passage of materials in and out of cell


Describe the intracellular face and the Extracellular face in relation to Plasma Membrane.

Intracellular face - side that faces cytoplasm

Extracellular face - side that faces outward


Describe Membrane Lipids

98% of molecules in plasma membrane are lipids


How do Phospholipids play a role in the Plasma Membrane?

75% of membrane lipids are phospholipids.

Amphiphilic molecules arranged in bilayer

Hydrophilic phosphate heads face water on each side of membrane

Hydrophobic tails - directed toward the center, avoiding water drift laterally from place to place.

Movement keeps membrane fluid


How does Cholesterol play a role in the Plasma Membrane?

20% of the membrane lipids

holds phospholipids still and can stiffen membrane


How do Glycolipids play a role in the Plasma Membrane?

5% of the membrane lipids

Phospholipids with short carbohydrate chains on extracellular face

Contributes to Glycoalyx - carbohydrate coating on the cells surface