Module 2A Membrane Structure Flashcards
encloses the cell, defines its boundaries, maintains essential differences between the cytosol and the extracellular environment, and supports ion gradients, protein sensors/receptors, and membrane proteins.
plasma membrane
What is the basic structural component of all cell membranes?
lipid bilayer
How much of the mass of animal cell membranes is made up of lipids?
50%
What property makes lipid molecules suitable for membrane formation?
amphiphilic - contain both hydrophobic and hydrophilic regions.
the most abundant membrane lipids, with a hydrophilic head and two hydrophobic hydrocarbon tails, forming the core of the lipid bilayer.
phospholipids
create kinks in the hydrophobic tail, which increases fluidity and prevents tight packing in the lipid bilayer.
cis-double bonds
- It is the main phospholipids.
- They have a three-carbon glycerol backbone, two long-chain fatty acids, and 3rd carbon is attached to a phosphate group linked to a head group.
phosphoglycerides
What is the main structure of phosphoglycerides? (3)
- three-carbon glycerol backbone
- two long-chain fatty acids
- 3rd carbon is attached to phosphate group linked to a head group.
Name three major types/classes of phosphoglycerides (most abundant ones in mammalian cell membranes and derived from glycerol)
- Phosphatidylethanolamine
- phosphatidylserine
- phosphatidylcholine
- Another important class of phospholipids derived from sphingosine rather than glycerol.
- derived from sphingosine, which includes a long acyl chain, an amino group, and two hydroxyl groups.
sphingolipids
Sphingolipids are derived from __, which includes a __, an __, and two __.
- sphingosine
- long acyl chain
- amino group
- hydroxyl groups
What is the most common type of sphingolipid?
sphingomyelin
Sphingomyelin has a __ attached to the amino group and a __ attached to the terminal hydroxyl group.
- fatty acid tail
- phosphocholine group (a simple molecule containing a choline group bonded to a phosphate group)
resemble sphingolipids but have sugars attached, often contributing to cell recognition and protection.
glycolipids
a sterol with a rigid ring structure, a single polar hydroxyl group, and a short nonpolar hydrocarbon chain. It helps modulate membrane fluidity and stability.
cholesterol
Phospholipids spontaneously form bilayers in aqueous environments due to their __ nature. Phospholipid molecules spontaneously __ to bury their __ tails, forming bilayers where tails are shielded inside, away from water.
- amphiphilic
- aggregate
- hydrophobic
structures with hydrophobic tails inward, formed when amphiphilic molecules aggregate in water at certain concentrations or conditions.
spherical micelles
Lipid bilayers have a __ where any small tear causes lipids to rearrange spontaneously to eliminate the free edge, often closing to form a sealed compartment.
self-sealing property
synthetic (artificial) lipid bilayers, which can be made in the form of spherical vesicles.
liposomes
How can the motion of individual lipid molecules in a bilayer be measured?
Fluorescence Recovery after Photobleaching (FRAP)
By constructing a lipid molecule with a fluorescent dye or small gold particle attached to its polar group, allowing observation of its diffusion.
like =N-O, is a modified lipid head group containing an unpaired electron. It produces a paramagnetic signal detected by electron spin resonance (ESR) to study lipid motion.
spin label
A spin label, like =N-O, is a modified lipid head group containing an unpaired electron. It produces a paramagnetic signal detected by __ (__) to study lipid motion.
electron spin resonance (ESR)
the rare migration of phospholipid molecules from one monolayer of a bilayer to the other.
flip-flop
It’s the quick exchange of places among lipid molecules within the same monolayer of a bilayer, allowing for membrane fluidity.
rapid lateral diffusion
What gives lipid molecules flexibility and rapid movement in the bilayer? (2)
- flexibility of hydrocarbon chains
- the rapid rotation of lipid molecules around their long axis
enzymes that catalyze the rapid flip-flop of phospholipids between monolayers in the lipid bilayer.
phospholipid translocators (flippases)
How does the composition of a lipid bilayer influence its fluidity? (2)
- lipid composition
- temperature
a change from a liquid state to a two-dimensional rigid crystalline state at a characteristic temperature
phase transition
enhances the permeability barrier, decreases deformability, and prevents hydrocarbon chains from crystallizing, modulating bilayer properties.
cholesterol
Archaeal bilayers are built from ______, differing in molecular design from those in most prokaryotes and eukaryotes.
20–25-carbon-long prenyl chains
Eukaryotic plasma membranes are highly varied, containing __ different lipid species, more diverse than those of prokaryotes and archaea.
500-200
specialized membrane microdomains that organize signaling molecules, influence membrane fluidity and protein trafficking, and regulate processes like neurotransmission and receptor trafficking.
- highly ordered and tightly packed lipid molecules
- contain high levels of sphingolipids, including gangliosides and cholesterol.
Lipid rafts
What process causes certain lipids to come together in separate membrane domains?
phase segregation
- store lipids within the cell
- surrounded by a single phospholipid monolayer that contains a variety of proteins.
lipid droplets
What types of cells are specialized for lipid storage?
fat cells/adipocytes
What kind of lipids form the contents of lipid droplets? (2)
Triacylglycerols and cholesterol esters, which are neutral and hydrophobic
What structure surrounds lipid droplets?
a single phospholipid monolayer that contains a variety of proteins.