Plasma Membrane • surrounds all living cells • separates cell contents from the cell’s external environment • responsible for transport of nutrients (and other substances) in and wastes (and other substances) out
Cell Membrane Structure • less than 10 nm thick • phospholipid bilayer • protein molecules embedded in bilayer • fluid mosaic model
Homework, p.86 #3 • When comparing the outside and inside halves of a cell membrane’s phospholipid bilayer, the composition of lipids on the two surfaces is asymmetrical. Describe how the membranes are asymmetric. Why is membrane asymmetry an important characteristics of cell membranes?
Phospholipids • hydrophobic tails, and hydrophilic heads • fluidity depends on type of fatty acids • sterols help to stabilize membrane
Homework, p.86 #6 • What is the function of sterols? Identify a sterol that is found in membranes of animal cells but not in plants or prokaryotes.
Membrane Proteins • wide variety of proteins • glycoproteins provide cells with unique markers • integral membrane proteins • polar/charged vs. non-polar amino acids • peripheral membrane proteins
Homework, p.86 #2 • When referring to membrane glycolipids and glycoproteins, what does the prefix “glyco” indicate?
Homework, p.86 #5 • What is meant by membrane fluidity? Explain how the chemical makeup of a membrane gives it fluidity. Which components affect the fluidity of a membrane? How is their movement related to this fluidity?
Homework, p.86 #9 • Explain the four functional categories of membrane proteins.
Membrane Proteins • 4 main functions: • transport • enzymatic activity • triggering signals • attachment and recognition