Lecture 2: Introduction to cellular membranes Flashcards
Textbook Chapter 4.1-4.2 and Lecture 2
Membranes are composed of
lipids
Overton (1980)
Dipped hair root in liquid, found that nonpolar solutes were more rapidly taken into the plant root hair as it was hdrophobic due to the membrane.
Gorter and Grendel (1925)
Showed that lipids extracted from a red blood cell (no other internal membrane bound organelles) membrane could cover the cell twice. Membranes are bilayer.
Membranes contains a bilayer of
phospholipids
Amphipathic
Both polar and nonpolar
Lipid bilayer prevents
random movements of substances in and out of the cell
Fatty Acids
long, unbranched hydrocarbon chains
Saturated
Lack double bonds
Unsaturated (2)
What it is+structure
- contains one or more double bonds
- introduces a bend in the fatty acid
Naturally occuring fatty ascids have — double bonds
cis
Phosphoglycerides are
phospholipids
Some sphinogolipids are
phospholipids
Phosphoglycerides (4)
membrane+backbone+components+often contains
- most membrane phospholipids are phosphoglycerides
- Built on a glycerol backbone
- Glycerol+2 fatty acid chains+phophate group+ additional group
- often contains one unstaturated and one saturated fatty acid chain
Overall charge for phosphatidic acid
-
Overall charge for phosphatidylcholine
neutral
Overall charge for phosphatidylserine
-
Phosphatidylethanolamine
neutral
Overall charge for phosphatidylinositol
-
Membrane lipids (3)
- phosphoglycerides
- sphingolipids
- cholesterol
Sphingolipids (6)
quanitity+what is it+property+head groups+fatty acid chain+roles
- less abundant membrane lipid
- built on sphingosine
- amphipathic
- additional groups can be linked to the head group
- Tend to have longer and more highly saturated fatty acid chains than phophoglycerides
- Roles in signal transduction, membrane structure, sensing
Ceramide (2)
- Example of sphingolipid
- spingosine+fatty acid
Spingolipids, if the addition is a carbohydrate, the molecule is a
glycolipid
Glycolipids, 2 subcategories:
A cerebroside: Carb addition of a simple sugar with ceramide
A ganglioside: Carb addition of a complex carbohydrate with ceramide
Membranes in the nervous system have a high abundance of
glycosphingolipids
Tay-sachs disease
Deficiency of the enzyme that normally breaks down GM2 ganglioside. Excess GM2 builds up in the brain and impairs the function of nerve cells
Membrane carbohydrates
% of the bonds
- 10% of membrane carbohydrates are covalently linked to lipids (glycolipids)
- 90% of membrane carbohydrates are covalently linked to proteins (glycoproteins)
All membrane carbohydrates in the plasma membrane face the
extracellular space
Myelin sheath is composed of
multiple layers of plasma membrane, with very little protein