4.3 Membrane
Biology Notes
Cell Membrane Function



Surrounds ___________________________________
Regulates cell’s ________________________________________________
o Maintains _______________________________________
 Maintains the same conditions constant inside the cell, regardless of the external
conditions
________________________ what enters and exits the cell
o ___________________________________________
 What does this mean?
 Examples: spaghetti strainers & mosquito netting
o What does the cell membrane allow into the cell?
o What does the cell membrane allow to exit the cell?
Membrane Structure:
1. Phospholipids
o These are lipids with _____________________________________________________________
o Fatty acids are _______________________________________
o The rest of the phospholipid is ___________________________________
o Draw a phospholipid and label glycerol, fatty acid, hydrophilic, hydrophobic, phosphate group
o What do phospholipids form? ________________________________
 Cell membrane has ___________________________________ of phospholipids
 Where are the “polar” heads of phospholipids? Why?

Where are the non-polar “tails” of the phospholipids? Why?
2. Cholesterol
o What type of molecule is a phospholipid? ______________________
 Is this molecule hydrophilic or hydrophobic?
 Where does cholesterol fit in the membrane?
o What is the function of cholesterol?
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4.3 Membrane
Biology Notes
 Helps ____________________________ the membrane
3. Membrane Proteins
o Membrane proteins have:
 ___________________________ regions & ________________________ regions
 Why are these important?
o Draw a membrane protein in a phospholipid bilayer. CIRCLE one phospholipid, BOX one
membrane protein, LABEL the hydrophilic & hydrophobic parts of the protein & phospholipids.
o What is the function of membrane proteins?
Fluid Mosaic Model:

Describes the _____________________________________
o How does it describe the membrane?
Concentration Recall:

What is concentration?

___________________________________: unequal distribution
particles (solute) in a solution
o How will particles move?

Equal concentration = _________________________________
of
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