Membrane bilayer dynamics and organization

Question 1

What is the composition of a membrane bilayer?

Answer 1

A membrane bilayer is primarily composed of phospholipids and proteins. and its a two dimensional fluid.

Question 2

What are the types of lipid movement in a lipid bilayer? lipid movement and diffusion in a lipid bilayer.

Answer 2

• Lateral diffusion: fast and unfavorable
• Rotational movement:
• Transbilayer movement: infrequent and unfavourable

Question 3

What is lateral diffusion of lipids characterized as?

Answer 3

Fast and favourable. the lateral diffusion of each of the lipid is different (unique).

Question 4

What is transbilayer diffusion of lipids characterized as?

Answer 4

slow and unfavourable.

Question 5

What effect does lipid composition have on membrane properties?

Answer 5

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

Question 6

How do saturated and unsaturated phospholipids differ in terms of membrane rigidity?

Answer 6

• Saturated phospholipids = more rigid
• Unsaturated phospholipids = more fluid

Question 7

What role does cholesterol play in membrane structure?

Answer 7

Higher cholesterol content leads to better packing of phospholipids, resulting in more rigidity and reduced water permeability.

Question 8

What are membrane rafts?

Answer 8

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.

Question 9

What is the significance of lipid asymmetry in a lipid bilayer?

Answer 9

The asymmetry is crucial for cellular functions, such as apoptosis and blood type determination.

Question 10

What happens when there is a loss of phosphatidylserine (PS) asymmetry?

Answer 10

loss of phosphatidylserine (PS) asymmetry leads to programmed cell death (apoptosis).

Question 11

What can defects in PS asymmetry cause?

Answer 11

defects in PS asymmetry cause Severe diseases, such as antiphospholipid syndrome (e.g., lupus erythematosus).

Question 12

Fill in the blank: Lipid bilayers are a ______.

Answer 12

[two-dimensional fluid]

Question 13

What is one example of how lipid bilayers differ within the same cell?

Answer 13

lipid bilayers differ within the same cel: Differences between the plasma membrane and the endoplasmic reticulum.

Question 14

True or False: Lipid rafts have unique roles in cells.

Answer 14

True.

Question 15

What is the relationship between saturated lipids and Van der Waals attraction?

Answer 15

Saturated lipids have greater Van der Waals attraction, allowing them to pack better together.

Question 16

What are the main lipids found in the outer and inner leaflets of the plasma membrane?

Answer 16

main lipids found in the outer and inner leaflets of the plasma membranePhosphatidylethanolamine
* Phosphatidylcholine Sphingomyelin * Glycolipids

Question 17

What is the consequence of genetic mutations affecting proteins that control PS in the membrane?

Answer 17

genetic mutations affecting proteins that control PS in the membrane can lead to autoimmune conditions.

Question 18

What makes lipid in a raft region like to hang out with one another and exclude others? what lipids fit better together?

Answer 18

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.

Question 19

Why does it matter that a lipid willl stay in the top leaflet and very rarely, spontanously flip to the bottom leaflet.?

Answer 19

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.

Question 20

Lipids bilayer can be made of different lipids:

Answer 20

with the same cell: plasma membrane versus endoplasmic reticulum
within the different cells: liver versus neuron.

Question 21

is the outter and inner leaflet of the plasma membrane the same?

Answer 21

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

Question 22

why ps (phosphatidylserine) is important what happens if the cell loses it?

Answer 22

1. 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.
2. Glycolipids asymmetry responsible for blood types. they are covalenty attah yto sugar.

Question 23

what happens in a normal healthy cell with ps or phosphatidylserine?

Answer 23

in a normal healthy cell, the Ps is inside the leaflet of the plasma membrane. and PS is inaccessible from the cell exterior.

Question 24

what happens to the cell that undergoes program cell death or apoptosis?

Answer 24

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.

Question 25

what are the conditions that are serious medically in PS?

Answer 25

some individuals have genetic mutations, that cause, some cell in the body to display PS on the outer membrane on healthy cells, even if it doesnt go under apoptosis. it generates an autoimmune condition.
Antiphospholipid syndrome. e.g. lupus erythematosus
the whole point is that PS is asymmetric in which part of the membrane it is found. it is supposed to be in the inner leaflet for health cells. only display in outer leaflets within cells going under cell death or apoptosi.