Eukaryotic Cell Membrane

Cell Membrane

• Cell membrane: the flexible boundary of a cell (also called a plasma membrane)

• It separates a cell from its surroundings.

• It allows nutrients to enter and waste to be removed.

Cell Membrane

• Homeostasis: maintaining a healthy balance

• The cell membrane allows some molecules into the cell and keeps others out.

Cell Membrane

• Selective permeability: allowing only certain molecules to enter and leave the cell

• Selective permeability is like a screen on a window

Cell Membrane

• What gets in?• H2O freely enters

cell• O2 in ,CO2 out• Na and Ca at

certain times in certain amounts

• Waste leaves but can’t reenter

Membrane Structure

• Phospholipid: lipid with a glycerol backbone and two fatty acid chains, and a phosphate group

Membrane Structure

• The polar head is hydrophilic: it likes water

• Fatty acid tail is hydrophobic: it does not like water.

• They form a bilayer

Membrane Structure

Membrane Structure

• The cell membrane also contains proteins to help support the cell structure.

• Cholesterol to keep the fatty acid tails from sticking together

Membrane Structure

• Fluid Mosaic Model: the organization of the cell membrane.

• Fluid because it is not fixed in a particular spot

• Mosaic because of the patterns the proteins make

Membrane Structure

• Proteins in the membrane function as:

• Transport proteins: moving molecules across the membrane

• Identify chemical signals