Plasma Membrane

Notes

CHARACTERISTICS:

• Maintains homeostasis (balance with environment)

• Selective permeability – allows some molecules into the cell while keeping others out.

Example of selective permeability – screen door keeps something out (bugs, pets, small children) and allows something through (small things)

STRUCTURE:

Phospholipids:• Lipids (fatty acid) with a phosphate

group attached.

• Polar head and non-polar tails

• Hydrophilic (likes water) head and hydrophobic (afraid of water) tail

Tail

Hydrophilic and Hydrophobic

Hydrophilic: “likes water”

Hydrophobic: “fears water” - repels water

Carrier Proteins• Found in plasma membrane (also

known as transport proteins)

• Allows larger substances to move through the plasma membrane.

Cholesterol molecule• Helps stabilize the phospholipids

• Prevents the fatty acid chains of the phospholipids from sticking together