p.8
Disease Processes Related to Membrane Rafts
What is the result of prion amplification in the system?
Plaques form, leading to neuron death.
p.4
Types of Membrane Rafts
Do all cells have lipid rafts?
No, not all cells have lipid rafts.
p.6
Signaling Mechanisms in Lipid Rafts
What three components are required for signal propagation in GPCR signaling?
GPCR, G protein, and effector.
p.6
Signaling Mechanisms in Lipid Rafts
What happens if GPCR, G protein, and effector are pre-clustered in a lipid raft?
Signaling happens immediately.
p.6
Signaling Mechanisms in Lipid Rafts
What occurs if G protein and effector are not in the lipid raft?
Dampening of the signal, leading to slower signaling.
p.5
Caveolin and Flotillin Characteristics
What distinguishes Float 1 and 2 from Caveolin?
They don’t deform the membrane.
p.5
Types of Membrane Rafts
Why are they called rafts?
Because they are isolated from the rest of the cell.
p.5
Types of Membrane Rafts
How are rafts isolated for study?
They float when isolated in sucrose density.
p.2
Resident vs Non-Resident Proteins in Rafts
Which types of proteins are considered non-resident signaling proteins?
Some G-proteins/G protein coupled receptors and non-receptor tyrosine kinases.
p.2
Cytoskeleton Functions
What is the role of cytoskeletal/adhesion proteins in membrane rafts?
They associate with actin/intermediate filaments and include cadherins and tight junctions.
p.2
Lipid Rafts Composition
Why are classical cadherins like E-cadherin not found in membrane rafts?
Because they have shorter transmembrane domains.
p.3
Lipid Rafts Composition
How does the thickness of the bilayer change in lipid rafts?
The thickness of the bilayer is increased.
p.3
Lipid Rafts Composition
How can proteins with longer transmembrane domains orient themselves in the membrane?
They can sit perpendicularly in the membrane.
p.1
Functions of Lipid Rafts
How do lipid rafts contribute to protein organization?
They concentrate and separate proteins within the plane of the bilayer.
p.10
Microtubules and Dynamic Instability
What is dynamic instability in microtubules?
The ability to grow and shrink.
p.10
Microtubules and Dynamic Instability
What does dynamic instability depend on?
A. Subunit critical concentration, B. Subunit temperature, C. GTP-beta-tubulin cap.
p.4
Caveolin and Flotillin Characteristics
What is Caveolin?
A protein that inserts itself in the membrane but is not a transmembrane protein.
p.4
Caveolin and Flotillin Characteristics
Where is Caveolin particularly abundant?
In the lung, specifically in epithelial cells.
p.6
Functions of Lipid Rafts
What is one function of membrane rafts in signaling?
They act as organizing centers for the assembly of signaling molecules.
p.6
Functions of Lipid Rafts
How do membrane rafts affect membrane fluidity?
They influence lateral diffusion, requiring the raft to float around the membrane if a protein moves laterally.
p.2
Resident vs Non-Resident Proteins in Rafts
What characterizes non-resident signaling proteins in membrane rafts?
They are affected by membrane rafts and can move in or out depending on the signal.
p.7
Disease Processes Related to Membrane Rafts
Why are prion diseases difficult to eliminate?
They cannot be killed with standard methods.
p.7
Disease Processes Related to Membrane Rafts
Do we have prion proteins in our brains normally?
Yes, normal prion proteins are present in our brains.
p.1
Lipid Rafts Composition
How do lipid rafts differ from the surrounding bilayer?
They are more ordered and tightly packed.
p.1
Functions of Lipid Rafts
What is the sweet spot of cholesterol for membrane fluidity?
A moderate amount increases fluidity.
p.1
Functions of Lipid Rafts
What role do lipid rafts play in cellular processes?
They compartmentalize cellular processes and serve as signaling platforms.
p.9
Lipid Rafts Composition
What is the role of cholesterol in membrane rafts?
Cholesterol is needed to maintain their rafts.
p.9
Challenges in Studying Lipid Rafts
What technique is used to analyze membrane rafts?
Sucrose density centrifugation.
p.9
Cytoskeleton Functions
What is the cytoskeleton?
A network of protein fibers that extend throughout the cytoplasm.
p.9
Cytoskeleton Functions
List one function of the cytoskeleton.
Cell adhesion and movement (migration).
p.9
Cytoskeleton Functions
What processes are facilitated by the cytoskeleton?
Endocytosis/exocytosis (secretion and recycling).
p.8
Signaling Mechanisms in Lipid Rafts
How do scrapie prions affect normal prion proteins?
Scrapie prions come into contact with normal prion proteins found in lipid rafts, causing the normal prion to change its confirmation.
p.8
Challenges in Studying Lipid Rafts
What is a main challenge in studying lipid rafts?
Limited methods available for studying lipid rafts in intact cells.
p.4
Caveolin and Flotillin Characteristics
How does Caveolin affect the membrane structure?
It curves the membrane into cave-like structures.
p.4
Caveolin and Flotillin Characteristics
What is Flotillin?
A protein that floats on lipid rafts.
p.7
Functions of Lipid Rafts
What processes are involved in the trafficking of membrane proteins?
Endocytosis or Golgi to the plasma membrane.
p.5
Types of Membrane Rafts
What happens to other membranes in the cell compared to flotillin?
Other membranes sink while flotillin floats.
p.3
Lipid Rafts Composition
What is the cholesterol concentration in raft bilayers compared to non-raft bilayers?
Increased [Cholesterol] is 2x more than in non-raft bilayers.
p.3
Lipid Rafts Composition
What types of proteins are enriched in lipid rafts?
Proteins containing Glycosylphosphatidylinositol (GPI) anchors and those with longer transmembrane domains.
p.5
Types of Membrane Rafts
Where are planar lipid rafts found?
In neurons, and they are high in Flotillin.
p.1
Lipid Rafts Composition
What are the main components of lipid rafts?
Cholesterol, sphingolipids, phospholipids, and specialized proteins (like caveolin and flotillin).
p.1
Functions of Lipid Rafts
What are the three main functions of lipid rafts?
Trafficking, signaling, and endocytosis.
p.1
Functions of Lipid Rafts
How do lipid rafts facilitate membrane traffic?
They assist in trafficking from the Golgi to the plasma membrane or in endocytosis.
p.9
Functions of Lipid Rafts
What does sequestration refer to in the context of membrane rafts?
Depletion or removal of components that causes the membrane raft to diffuse into a regular membrane.
p.9
Challenges in Studying Lipid Rafts
What is required for sucrose density centrifugation?
Homogenization to break up membranes.
p.9
Cytoskeleton Functions
How does the cytoskeleton contribute to cell shape?
It provides structure and support.
p.8
Challenges in Studying Lipid Rafts
Why is it difficult to study lipid rafts using light microscopy?
Lipid rafts are too small to be resolved by light microscopy.
p.6
Signaling Mechanisms in Lipid Rafts
Can GPCRs be mixed and matched in lipid rafts?
Yes, it is not always the GPCR that is in the lipid raft.
p.2
Lipid Rafts Composition
What are the three main types of proteins found in membrane rafts?
Resident proteins, non-resident signaling proteins, and cytoskeletal/adhesion proteins.
p.2
Lipid Rafts Composition
What are examples of resident proteins in membrane rafts?
Caveolin, Flotillin, and GPI-anchored proteins (e.g., prion protein).
p.7
Disease Processes Related to Membrane Rafts
What is the role of lipid rafts in prion disease?
They facilitate the conversion of normal prion protein (PrPc) to abnormal proteins (PrPsc).
p.5
Types of Membrane Rafts
What are the two types of membrane rafts?
Caveolae and planar lipid rafts.
p.5
Caveolin and Flotillin Characteristics
What are caveolae?
Small, flask-shaped invaginations of the plasma membrane high in Caveolin.
p.5
Signaling Mechanisms in Lipid Rafts
What roles can Caveolin and Flotillin play in signaling?
They can promote or dampen signaling.
p.3
Lipid Rafts Composition
What are the two ways transmembrane proteins can insert themselves?
1. Sideways via the secretory pathway 2. Straight via lipid rafts from the Golgi to the membrane.
p.3
Lipid Rafts Composition
What is the significance of longer transmembrane domains in raft proteins?
They allow for increased thickness and perpendicular orientation in the membrane.
p.10
Microtubules and Dynamic Instability
What are microtubules composed of?
Polymers of alpha and beta tubulin dimers.
p.10
Microtubules and Dynamic Instability
What are protofilaments?
A line of ab dimers forming the structure of microtubules.
p.10
Microtubules and Dynamic Instability
What factors influence dynamic instability?
A. Assembly (polymerization), B. Disassembly (catastrophe), C. Reassembly (rescue).
p.10
Microtubules and Dynamic Instability
How does temperature affect microtubules?
Microtubules do not function well at low temperatures; things slow down.
p.10
Microtubules and Dynamic Instability
At what temperature do microtubules grow best?
At body temperature, not below 60 degrees Celsius.
p.9
Cytoskeleton Functions
What role does the cytoskeleton play in mitosis?
It is involved in mitosis and cytokinesis.
p.10
Microtubules and Dynamic Instability
What happens to GTP-bound tubulin at low temperatures?
It cannot reach the growing end fast enough, leading to fraying.
p.10
Microtubules and Dynamic Instability
Why is the GTP-beta-tubulin cap important?
It is necessary for maintaining the growing end of microtubules.
p.9
Cytoskeleton Functions
How does the cytoskeleton contribute to muscle contraction?
It facilitates muscle contraction.
