Fluid Mosaic model, membrane proteins, and movement across membranes Flashcards
What are the components of a cell membrane [3]?
1) Lipids
2) Proteins
3) Carbohydrates (Attached to glycolipids and glycoproteins)
Phospholipids:
- Head is a polar hydrophilic and tail is a nonpolar fatty acid (amphipathic molecule)
- Shape of a structure is determined by ratio of head to tail
- Forms a bilayer in water because of polarity
How do liposomes form?
Phospholipids in water with a neutral pH form a spherical bilayer that surround whatever potential macromolecule was captured from the system.
How does cholesterol impact the fluidity of a membrane?
Can increase or decrease depending on the temperature:
At typical cell temperatures, cholesterol decreases fluidity.
At low temperatures, it increases fluidity.
Functions of membrane proteins [4]:
1) Transporters (moves ions across membrane)
2) Receptors (receives signals from the environment)
3) Enzymes (catalyze chemical reactions)
4) Anchors (attach to other proteins)
What are the two groups of membrane proteins?
1) Integral membrane proteins
2) Peripheral membrane proteins
What is an integral membrane protein?
Proteins that are permanently associated with the cell membranes.
What are peripheral membrane proteins?
Temporarily associated with the lipid bilayer or with integral membrane proteins through weak covalent forces.
How do transmembrane proteins work?
They span the entire lipid layer with a hydrophobic section that spans the membrane and two hydrophilic sections on either side.
What is FRAP?
Fluorescent Recovery After Photobleaching. This process was used to prove that proteins move in the membrane plane.
->Area of membrane is bleached
->Fluorescent dye is attached to proteins
-> Bleach spot becomes fluorescent indicating proteins moved
What is the fluid mosaic model?
Idea that lipids and proteins coexist in the plane of the plasma membrane moving laterally.
How is homeostasis maintained within a cell?
The plasma membrane is selectively permeable, meaning it lets certain molecules in and out under certain conditions.
What is passive transport?
This is when something enters the cell through diffusion. Oxygen and carbon dioxide move in this way.
Types of membrane transports [2]:
1) Channel
2) Carrier
How does a channel transport work?
It provides a channel for molecules of certain shape and size to pass through.
How do carrier transporters work?
This binds to and then transports specific molecules. They can either be open to the inside or outside of the cell.
What is osmosis?
Solvent like water moving across a selectively permeable membrane from a region of lower solute concentration to a region with higher solute concentration.
What is osmotic pressure?
The tendency of a solution to draw in solvent by osmosis
What is active transport
When molecules that cells need are not highly concentrated in its environment, it needs to be actively transported which requires energy.
How does the sodium-potassium pump work?
Sodium has to move out of the cell and potassium needs to move in–both against gradients. The antiporter transport proteins use energy from adenosine triphosphate to do this.
Where do phospholipids come from?
Fatty acids are activated in the cytosol, then they bond to glycerol-phosphate and are inserted into the ER. From there enzymes and protein work together to synthesize.
Factors affecting membrane fluidity [3]:
1) Temperature
2) type of lipid (saturated increases, unsaturated decreases)
3) Cholesterol
Types of ion channels [2]:
1) Voltage-gated: open/close in response to changes in membrane charge
2) Ligand-gated: open when molecule binds to channel
Toxins on ion channels [2]:
1) Tetrodotoxin blocks voltage gated channels stopping nerve signals
2) Curare blocks acetylcholine receptors causing muscle paralysis
