plasma membrane Flashcards
What are the primary roles of membranes?
Physical barriers to the environment.
Acts a site for biochemical reactions
helps keep the cells alive by generating electrochemical gradient that is a major source of energy for the cell
How do cells exchange materials for catabolism and waste?
Cells utilize membranes to facilitate the exchange of materials.
How do cells sense their surroundings for resources and threats?
Cells use membranes to detect environmental signals.
What are the sites for biochemical activities in membranes?
Hydrophobic regions facilitate pigment/lipid synthesis and intermolecular interactions.
What is the most fundamental energy source for keeping cells alive?
Electrochemical gradients.
What is the structure of a membrane bilayer?
Formed by polar heads and lipid tails that spontaneously close into a vesicle.
What factors determine the diffusion rate across membranes?
High diffusion occurs with less interaction and packing; low diffusion occurs with more interaction and packing.
What are the general characteristics of a lipid membrane bilayer?
form vesicles
selective permeability
What are phosphoglycerides?
The most abundant lipids with two fatty acids, typically one or more unsaturated.
What are sphingolipids?
Sphingosine-based lipids with one hydrocarbon chain, reducing fluidity.
What role does cholesterol play in membranes?
Acts as a fluidity buffer, stabilizing membrane fluidity at varying temperatures.
How does temperature affect cholesterol’s role in membranes?
At high temperatures, it reduces fluidity; at low temperatures, it prevents tight packing.
What drives lipid bilayer assembly?
Hydrophobic interactions among phospholipid tails.
What is selective permeability in membranes?
The bilayer acts as a barrier to polar and charged molecules while allowing small nonpolar molecules to pass.
How is bilayer symmetry vs. asymmetry established?
Through enzyme modifications and lipid transport proteins.
What techniques are used to study membrane structure?
Freeze-fracture technique and electron microscopy.
What is the fluid mosaic model?
Predicts lateral diffusion of lipids and proteins in the membrane.
What types of proteins are found in membranes?
Integral proteins (transmembrane, monolayer, lipid-linked) and peripheral proteins.
How are proteins localized on membranes?
By using hydrophobic or amphipathic structures.
What functions do membrane proteins serve?
Transporters, anchors, receptors, and enzymes.
