Membrane bilayer dynamics and organization Flashcards
What is the composition of a membrane bilayer?
A membrane bilayer is primarily composed of phospholipids and proteins. and its a two dimensional fluid.
What are the types of lipid movement in a lipid bilayer? lipid movement and diffusion in a lipid bilayer.
- Lateral diffusion: fast and unfavorable
- Rotational movement:
- Transbilayer movement: infrequent and unfavourable
What is lateral diffusion of lipids characterized as?
Fast and favourable. the lateral diffusion of each of the lipid is different (unique).
What is transbilayer diffusion of lipids characterized as?
slow and unfavourable.
What effect does lipid composition have on membrane properties?
Composition affects function and properties, such as rigidity and fluidity.
Saturated phospholipids = more rigid VERSUS unsaturated = more fluid
* Higher cholesterol content = better packing of phospholipids = more rigid
and reduced water permeability
How do saturated and unsaturated phospholipids differ in terms of membrane rigidity?
- Saturated phospholipids = more rigid
- Unsaturated phospholipids = more fluid
What role does cholesterol play in membrane structure?
Higher cholesterol content leads to better packing of phospholipids, resulting in more rigidity and reduced water permeability.
What are membrane rafts?
Membrane rafts are parts of the membrane enriched in specific lipids such as saturated lipids and cholesterol. lipid because made of lipid and rafts because they are kind of rafts on a lake or ocean, like something floating on something else.
it influences other things going to the membrane.
What is the significance of lipid asymmetry in a lipid bilayer?
The asymmetry is crucial for cellular functions, such as apoptosis and blood type determination.
What happens when there is a loss of phosphatidylserine (PS) asymmetry?
loss of phosphatidylserine (PS) asymmetry leads to programmed cell death (apoptosis).
What can defects in PS asymmetry cause?
defects in PS asymmetry cause Severe diseases, such as antiphospholipid syndrome (e.g., lupus erythematosus).
Fill in the blank: Lipid bilayers are a ______.
[two-dimensional fluid]
What is one example of how lipid bilayers differ within the same cell?
lipid bilayers differ within the same cel: Differences between the plasma membrane and the endoplasmic reticulum.
True or False: Lipid rafts have unique roles in cells.
True.
What is the relationship between saturated lipids and Van der Waals attraction?
Saturated lipids have greater Van der Waals attraction, allowing them to pack better together.
What are the main lipids found in the outer and inner leaflets of the plasma membrane?
main lipids found in the outer and inner leaflets of the plasma membranePhosphatidylethanolamine
* Phosphatidylcholine Sphingomyelin * Glycolipids
What is the consequence of genetic mutations affecting proteins that control PS in the membrane?
genetic mutations affecting proteins that control PS in the membrane can lead to autoimmune conditions.
What makes lipid in a raft region like to hang out with one another and exclude others? what lipids fit better together?
Lipid rafts are regions of membranes with unique lipids and proteins and have
unique roles in cells by organizing these molecules.
Saturated lipids pack better together than unsaturated lipids. therefore saturated/planar lipids have greater van der Waals attraction.
- spend more time together than with unsaturated lipids. saturated hydrocarbon chains are packed well. unsaturated hydrocarbon chains with cis-double bonds not packed well.
the region that hydrocarbons pack well or rafts region are thicker than the region with unsaturated hydrocarbons.
saturated are better than unsaturated.
lipids can move quickly but they can’t just move as fast.
so these are aspects of lateral diffusion: some lipid packs together and exclude others, which is moving side to side in the lipid bilayer, packing side by side.
Why does it matter that a lipid willl stay in the top leaflet and very rarely, spontanously flip to the bottom leaflet.?
It can creat asymmetric. it meaans that the top leaflet if lipid bilayer can actualyy have different lipids than the bottom leaflet. tehy are not the same thast why they are asymmetry. and trhey are no spontaneously mixed.
Lipids bilayer can be made of different lipids:
with the same cell: plasma membrane versus endoplasmic reticulum
within the different cells: liver versus neuron.
is the outter and inner leaflet of the plasma membrane the same?
The plasma membrane is a lipid bilayer, it has a top leaflet that faces the outside of the membrane and a leaflet bottom that faces the cytosol.
the outter and inner leaflet of the plasma membrane are not the same. there are diiferent roteins and charges on each side of the membrane, the face towards cytosol some of them has a negative charge and negatively charged glycophospholipids are called phosphatidylserine also tehres phosphatidylethanolamine. an its in the inner leaflet.
other lipids that are on the outer leaflet, phosphatidylcholine, sphingomyelin, and glycolipids.
Example of functions:
1. Loss of PS ( phosphatidylserine) asymmetry leads to programmed cell death – ______________
2. Glycolipids asymmetry responsible for blood types.
apoptosis
why ps (phosphatidylserine) is important what happens if the cell loses it?
- Loss of PS asymmetry leads to programmed cell death apoptosis.
the reason why immune system attacks cells that undego apoptosis is becasue it has a role in cancer. its one of the ways in which immune system can actully benefit proteins and get rid of cancers. when the immue system sess a cell dying to prevent swelling and damage to the body they just get rid of them. - Glycolipids asymmetry responsible for blood types. they are covalenty attah yto sugar.
what happens in a normal healthy cell with ps or phosphatidylserine?
in a normal healthy cell, the Ps is inside the leaflet of the plasma membrane. and PS is inaccessible from the cell exterior.
what happens to the cell that undergoes program cell death or apoptosis?
Apoptosis triggers cells to display PS on the cell surface. It doesn not happen spontaneously the cell forces this to happen. and the immune system gets rid of that cell.
