Cells 1.3 Membrane Flashcards
Outline the structure of a phospholipid layer.
Hydrophilic heads (phosphate group, glycol) and Hydrophobic tails (2 fatty acids)
What does amphipathic mean?
Amphipathic means that the organism is partly hydrophilic as well hydrophobic, like a phospholipid.
How is the phospholipid bilayer maintained?
The hydrophilic heads are pointed outwards. They are attracted to the water inside and outside of the cell. The hydrophobic tails are pointed inwards as they avoid contact with the water. They are also attracted to each other. The nature of amphipathic nature of phospholipids helps to ensure stability of the plasma membrane.
How did the evidence from electron microscopy support the Davson and Danielli model?
In their model, the phospholipid layer is sandwiched by two layers of protein as they know that they contain protein due to the evidence of membranes being isolated from red blood cells contain protein. This as well as the fact that the surface of an actual biological membrane is more wettable than an artificial, lead them to think that membranes are coated by protein which absorb the water.
How was the Davson and Danielli model proven wrong by Singer Nicholson?
A membrane with an outside layer of protein would not be stable as it block the absorbance of water for the hydrophilic part of the phospholipid. Membrane proteins can change their positions within the lipid layer. So, the new model showed that Proteins are individually embedded in the lipid layer. This lets the hydrophilic portions expose to its maximum to water which keeps the layer stable.
Draw a full 2D diagram of a phospholipid layer. Label it.
- Phospholipid bilayer (hydrophilic head & hydrophobic tails)
- Cholesterol
- Glycoprotein
- Integral proteins
- Peripheral proteins.
What is the function of cholesterol?
Cholesterols are part of animal membranes. They make the layer less fluid.
What is a protein called that goes all the way through the bilayer?
An integral protein.
What is a protein called that does not reach all the way through the bilayer?
a peripheral protein
