Quiz 1 Flashcards
Ways membrane phospholipids can move?
- lateral diffusion within monolayer
- rotation
- flexion (inflection/flexing)
- flip flop (rare, maybe once a month)
Roles of plasma membrane:
- selective permeability, barrier/protection
- cell communication
- import and export of molecules
- cell growth and motility
Ways to influence fluidity of the cell membrane:
- shorter tails (less interaction with neighbors, more fluid)
- double bonds, kinds (unsaturated have less interactions, more fluid)
- cholesterol sits between phospholipids (sterol adds rigidity)
How is Cholesterol like other lipids?
amphipathic (polar head group), sterol
What is major lipid component of plasma membrane?
Phospholipids, with hydrophilic head and 2 hydrophobic tails, amphipathic
Where are membranes made?
ER, more phospholipids made in the cytosolic half of the bilayer
What is scramblase?
Found at ER. Catalyzes transfer of random phospholipids from one monolayer to another. Results in symmetry of growth and length.
Where does asymmetry distribution (typical in animals) occur?
Golgi lumen. Flippase catalyzes transfer of specific phospholipids to cytosolic monolayer.
What is found more on the extracellular face?
- Sphingomyelin (SM)
- Glycolipids and other carbs on sugar coating
- Phosphatidylcholine (PC)
What is found more on the cytosol face?
- Phosphatidylethanolamine (PE)
- Phosphatidylserine (PS)
- Phosphotidylinositol (PI??)
Functions of glycomatrix
- cell recognition
- cell detection
- distinguish cells (unique)
Where are glycolipids formed?
Golgi
Some categories of plasma proteins:
- transporters/channels (Ion channels, Na+ pump)
- anchors (integrins)
- receptors (PDGF)
- enzymes (protein catalysts)
What are the two ways proteins associate with the plasma membrane?
Integral membrane proteins and peripheral proteins (includes protein-attached).
What are three kinds of integral membrane proteins?
- Transmembrane
- Monolayer-associated
- Lipid-linked
A Polypeptide Chain Usually Crosses the Lipid Bilayer as…
an alpha-helix. A transmembrane hydrophilic pore can be formed by multiple amphipathic alpha helices.
Why is an alpha-helix likely the most common way for proteins to span the membrane?
Hydrophobic amino acid side chains stick out. Hydrogen bonding (peptide bonds?) hold configuration?? They create a hydrophilic passageway for charged and large molecules to pass through.
How do beta-sheets commonly manifest?
Form beta-barrels. Porins, that are found on the outer membrane of mitochondria, archaea, and bacteria.
Why is it difficult to study membrane proteins?
- Hard to isolate from membrane
- Very difficult to crystallize
What are detergents and what are the most common ones used?
Membrane Proteins Can Be Solubilized in Detergents. SDS gels and Triton X-100 (only have one hydrophobic tail) used to isolate membrane proteins.
What is a cell cortex?
A network of proteins that gives structure and shape to animal cells. Sits underneath plasma membrane.
What types of cells have a cell wall?
Bacteria, archaea, plant cells, and fungi. Mainly used for protection, but also limits movement.
What is Bacteriorhodopsin?
A proton pump.
What is principle component of red blood cell cortex?
Spectrin. Gives an important biconcave shape.
What is more present in muscles and other animals?
Actin and myosin. (responsible for cell movement)
What did the fusion of a mouse and human cell show?
That membrane proteins moved and intermingled.
