Lesson 2A - Cell Membrane Flashcards
It is referred as the gateway to the cell.
Cell Membrane
It:
1. Acts as a boundary
2. controls what enters and leaves cell
3. Regulates chemical composition
4. Maintains homeostasis
Cell Membrane
What property does the cell membrane have that allows UNICELLULAR organism to move?
Flexible
It provided the first evidence that biological membrane consist of lipid bilayers.
Studies of the red blood cell plasma
Fill in the blanks:
The cell membrane is _________ and allows a _________ _________ to move
flexible, unicellular organism
What did the red blood cell plasma studies proved about biological membranes?
Provided first evidence that the biological membranes were consisted of lipid bilayers.
The three Plasma Membrane Models:
- Sandwich Model
- Unit Membrane Model
- The Fluid Mosaic Model
It was proposed by Danielli and Davson, a model where they believe that the cell membrane is made up of two globular proteins with phospholipid inside to make a layer and then join two layers together to make a channel for molecules to pass.
Sandwich Model (Danielli-Davson Model)
It was proposed by Robertson. where it was a more refined version of the Sandwich Model.
It theoried that the outer layer of protein has a phospholipid bilayer inside.
All cells were of the same composition.
However, can’t explain how molecules pass through the use of proteins with non polar parts.
Unit Membrane Model (Robertson Model)
Proposed by Singer and Nicholson, described as the presence of Phospholipid bilayer with proteins either partially or fully embedded.
Electron micrographs or freeze-fractured membrane is also evident.
The Fluid Mosaic Model
Among the three membrane model, which is the most correct?
The Fluid Mosaic Model
Among the three models, what four reason made the Fluid Mosaic Model the correct one?
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 surfac
It is the basic paradigm of biological
membrane structure
The Fluid Mosaic Model
How were the lipids in a membrane organized?
Liquid Crystalline Lattice
What happens to the liquid crystalline lattice organization of the lipids in the membrane once it reaches the transition temperature?
becomes a frozen crystalline gel
Why is it that plasma membrane is composed of two layers of lipids?
It means that atleast a portion of the membrane repels the water that constantly surrounds it.
This evades the possibility of the allowing of too much water in the cell which may cause the cell to burst.
Why is the Fluid Mosaic Model attributed as “Fluid”?
Due to its consistency (olive oil) at body temperature, due to unsaturated phospholipids.
Phospholipids and proteins move around freely within the layer, like liquid.
What moves freely within the cell membrane like liquid?
Phospholipids and Proteins
What is the consistency of plasma membrane being compared to at body temperature?
Olive Oil
What makes the Fluid Mosaic Model affiliated with the term “Mosaic”?
The presence of different types of proteins (50 types) that forms a collage at either side of the membrane and from cell to cell.
What part of the membrane is Hydrophilic, facing out?
Heads
What part is Hydrophobic, facing in?
Tails
What produces the mosaic pattern of the Fluid Mosaic Model?
Scattered protein molecules when membrane is viewed from above.
What happens to the hydrocarbons/ phospholipids at low temperatures?
They go tightly packed
What happens to the hydrocarbon/phospholipid at high temperatures?
They move to fluid phase, allowing movement.
