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