2a. Cell Membrane Structure Flashcards
(95 cards)
What is a cell membrane?
- Acts as a boundary
- Controls what enters and leaves cell
- Regulates chemical composition
- Maintains homeostasis
Why is cell membrane call the gateway to the cell?
cell’s outer membrane acts as a gate, preventing intruders from invading the cell.
What is the importance of the cell membrane?
main role is to provide protection to the cell from its surroundings. It controls the passage of some solutes and water into and out of the cell.
The cell membrane in unicellular organisms is
flexible and allows to
move
Studies of the red blood cell plasma
membrane provided ____
the first evidence that
biological membranes consist of lipid bilayers.
The role of the cell membrane in the plant cell is ____
to separate the cytoplasm of the cell from its cell wall.
Sandwich model was proposed by?
Danielli and Davson
3 Plasma Membrane Model
- Sandwich Model
- Unit Membrane Model
- Fluid Mosaic Model
What is fluid mosaic model?
Phospholipid bilayer with proteins partially or fully imbedded, seen with freeze-fractured membrane via electron micrographs
What is sandwich model?
2 layers of globular proteins with phospholipid inside to make a layer and then join 2 layers together to make a channel for molecules to pass
Who proposed unit membrane model?
Robertson
What is the outer layer of PPL bilayer?
glycoprotein coat
What is unit membrane model?
- Outer layer of protein with phospholipid bilayer inside,
- believed all cells same composition,
- does not explain how some molecules pass through or the use of
proteins with nonpolar parts - used transmission electron microscopy
Who proposed fluid mosaic model?
Singer and Nicolson
Process on how to verify the correct membrane model?
1) Rapidly freeze specimen
2) Use special knife to cut membrane in half
3) Apply a carbon + platinum coating to the surface
4) Use scanning electron microscope to see the surface
According to the electron micrograph which membrane model is correct?
Fluid-Mosaic Model
What model is the Basic paradigm of biological
membrane structure
Fluid-mosaic model
The lattice becomes ____ at
the transition temperature.
frozen crystalline gel
The lipids in a membrane are organized into a
_____
liquid crystalline lattice.
What composes in FM model freeze-fracture?
there is a P face and E surface, extracellular surface of membrane
What composes in FM model section?
bimolecular lipid leaflets (trilaminar)
The Plasma Membrane is composed of two layers of lipids. Why is this important?
Having lipids in the plasma membrane means that at least a portion of the membrane repels the water that constantly surrounds it. Allowing
too much water inside the cell could cause the cell to burst.
2 Layers of the FM Model
- Fluid
- Mosaic
Describe the fluid in FM Model
plasma membrane has consistency of olive oil at body temperature, due to unsaturated phospholipids