Membrane Structure

Question 0

Gorter & Grendel (1925)

Answer 0

• Lipids can organize in a variety of different configurations (Momo,bi,tri)
• Studied Erythrocytes (only plasma membranes)
• Used Langmuir Trough to determine lipid surface area
• Found a 2:1 ratio = Bilayer

Question 1

Phospholipid Bilayer

Answer 1

• Glycerol backbone
• Ester Linked
• Hydrophilic Head
• Hydrophobic Tail

Question 2

Problems with Gorter & Grendel’s Work

Answer 2

• Underestimated surface area of the cells (biconcave shape)
• Underestimated the total surface area of the lipid (acetone extracts 75%)
• The two errors cancelled each other out*

Question 3

Davson & Danielli (1935)

Answer 3

• Recognized that membranes contain Proteins as well as pl-bilayer
• Proposed that proteins coated the surface of membrane bilayer
• Also proposed that lipids and cholesterol were found within the bilayer like a sandwich

Question 4

Linus Pauling

Answer 4

-Recently described globular configurations of protein structure

Question 5

X-Ray Crystallography (1950)

Answer 5

• Used to study membrane structures
• Required a crystal - organized structure with repeating patterns
• Used Myelin membranes for this
• Suggested that membrane lipids were organized in a bilayer structure
• Established the thickness of a membrane (70-75A)

Question 6

J.D. Robertson (1959)

Answer 6

-Used Transmission Electron Microscopy (TEM) to study membrane
-Seen both blood and myelin membranes have a “trilaminar” structure or railroad track
-Proposed “Unit membrane model”
>proteins were sheet-like
>transport channels lined the proteins
> non-lipid components within the bilayer

Question 7

Singer & Nicolson (1972)

Answer 7

-Proposed the “Fluid Mosaic Model”
>Intrinsic proteins Embedded, Extrinsic proteins on surface
*Mosaic=Pictures made of lots of diff pics
-Membrane is 2-dimensional fluid allowing mobility
-Thermodynamically stable=not much work needed