Module 2A - Membrane Structure Flashcards
Enclose the cell, defines its boundaries, and maintains the essential difference between the cytoplasm and the extracellular matrix.
Plasma membrane
Maintains the characteristic differences between the contents of each organelle and the cytosol.
Plasma membrane
Components of the plasma membrane:
- Ion gradients
- Protein receptors or sensors
- Lipid bilayer
- Membrane proteins
The main structural component of all cell membrane.
Lipid bilayer
Lipid make about ___% of the total mass of most animal cells.
50%
Lipid molecules are __________, which means they have a hydrophobic and a hydrophilic sides.
Amphiphilic
The most abundant type of membrane lipids.
Phospholipids
Parts of a phospholipid:
- Phosphate head (Hydrophilic)
- Two hydrocarbon tails (hydrophobic)
Bonds that creates the slight deformation on a phospholipid tail.
cis-double bonds
Different types of lipids in the cell membrane:
- Phosphoglycerides
- Sphingolipids
- Glycolipids
What is the main type of phospholipid?
Phosphoglycerides
Characteristics of Phosphoglycerides:
- Three-carbon glycerol backbones
- Two long chains of fatty acids
- 3rd carbon attached to a phosphate group
Type of lipid from sphingosine (long acyl chain with an amino group and two hydroxyl groups)
Sphingolipids
Most common type of Sphingolipids:
Sphingomyelin
Sub-types of phosphoglycerides:
- Phosphatidylethanolamine
- Phosphatidylserine
- Phosphatidylcholine
Type of lipid that resembles sphingolipids with a carbohydrate attached through a glycosidic bond.
Glycolipids
A sterol that contains a rigid ring structure, where a single polar hydroxyl group and a short non-polar hydrocarbon chains are attached.
Cholesterol
The shape and amphiphilic characteristic of the phospholipid molecules causes them to form:
bilayers spontaneously in an aqueous environment.
Aggregation of phospholipids that cause them to bury their hydrophobic tails inward, forming a sphere.
Spherical micelles
Aggregation of phospholipids that cause them to bury their hydrophobic tails inward, sandwiching them in between.
Bilayer/Lipid bilayer
The phospholipid layer forms into a sphere, closing the gaps to seal the hydrophobic tails exposed to water because it is:
Energetically favorable
What molecules are able to diffuse directly through the plasma membrane?
Lipid molecules
The characteristic of molecules to rapidly exchange places with their neighbors within a monolayer.
Rapid lateral diffusion
The rare migration of phospholipid molecules from one side of the monolayer into the other side.
Flip-flop
Catalyzes the rapid flip-flop of phospholipids from one monolayer to the other.
Phospholipid translocator (flippases)
Lipid component that allows the molecules of the plasma membrane to freely move laterally.
Two-dimensional fluid
The change of the two-dimensional fluid from a liquid state, into a rigid crystalline state at characteristic temperatures.
Phase transition
How does cholesterol regulates the properties of the lipid bilayer?
- Enhances the permeability-barrier properties
- Makes the lipid bilayer less deformable; decreases the permeability of the bilayer from small water molecules
- Prevents the hydrocarbon chains from coming together and cystalizing
Plasma membranes of most _______ are more varied than prokaryotes and archaea
Eukaryotic cells
How many different species of lipids are there?
Around 500-200 species
Membrane microdomains that serves as organizing centers for assembly of signaling molecules, influence membrane fluidity, trafficking of membrane proteins, regulate cellular processes, and receptor trafficking.
Lipid rafts
Specific lipids come together in separate domains.
Phase segregation
Where lipids are stored (e.g. fat cells or adipocytes). Forms rapidly when cells are exposed to high concentration of fatty acids.
Lipid droplets
Specialized cells for lipid storage
Adipocytes (fat cells)
Types of neutral lipids:
Triacylglycerols and cholesterol esters
A condition where two monolayers have different compositions. Important in converting extracellular signals into intracellular ones.
Lipid asymmetry
Lipid that moves from the inner monolayer of the bilayer to the outer monolayer when the cell undergoes apoptosis (cell death).
Phosphatidylserine
Cleaves an inositol phospholipid within the cytosolic monolayer to create fragments that activates protein kinase C, and stimulates the release of Ca2+ from the endoplasmic reticulum.
Phospholipase C
Sugar-containing lipid molecule with the most extreme asymmetry in their membrane distribution. Occurs in all eukaryotic plasma
Glycolipids
The function of glycolipids vary from their:
Location/Localization
Exposed apical surface; may help to protect the
membrane against the harsh conditions.
Epithelial cells
Charged glycolipids; important because of their electric effects
Gangliosides
Performs most of the membrane’s specific tasks and therefore give each type of cell membrane its
characteristic functional properties.
Membrane proteins
Type of membrane protein that extends throughout the lipid bilayer, located entirely on the cytosol, and are attached to the cytosolic monolayer.
Transmembrane proteins
Membrane protein that is not found in the hydrophobic interior, but is bound to either sides of the membrane by non-covalent interactions.
Peripheral proteins
Controls the membrane localization of some signaling proteins.
Lipid anchors
The membrane-spanning segment of
the polypeptide chain that contacts the hydrophobic area of the lipid bilayer are formed into:
α-helix
A polypeptide chain that spans the lipid bilayer only once.
Single-pass transmembrane proteins
Used to localize potential α-helical membrane spanning segments in a polypeptide chain.
Hydropathy plots
It is estimated that about ___% of an organisms proteins are transmembrane proteins
30%
Multi-pass transmembrane strands of a polypeptide chain are arranged to be a:
β sheet that is rolled up into a cylinder
Many membrane proteins are:
Glycosylated
They extensively coat the surface of all eukaryotic cells:
Carbohydrates
__________ chains are always present on the non-cytosolic side of the plasma membrane.
Oligosaccharide
Stabilizes either the folded structure of a polypeptide chain, or its association with other polypeptides. Forms on the non-cytosolic side of the membrane.
Disulfide bonds
Small amphiphilic molecules that disrupts hydrophobic associations and destroy the lipid bilayer, solubilizing the membrane proteins.
Detergents
Polar side of detergents can be either:
Ionic or non-ionic
Surfactant concentration at which micelle formation is first seen in the solution.
Critical micelle concentration
How does detergents work on solubilizing membranes?
Hydrophobic ends of detergent binds with the hydrophobic regions of the membrane, where they displace the lipid molecules.
Small, uniformly sized patches of membrane that are surrounded by a belt of protein, which covers the exposed edge of
the bilayer to keep the patch in solution.
Nanodiscs
Membrane proteins can often function as a part of large:
Multicomponent complexes
How does membrane proteins able to move laterally across the lipid bilayer?
Lateral diffusion
Procedure that measures the rate of lateral diffusion by the membrane proteins.
Fluorescence recovery after Photobleaching (FRAP)
Procedure that labels individual membrane molecules and tracks their movement by video microscopy.
Single-particle tracking
FACT: Cells are capable of confining/distributing membrane proteins across specific regions in the cells.
This asymmetric distribution of membrane proteins is often essential for the function of the epithelium.
Asymmetric distribution of ___________ is often essential for the function of the epithelium.
Membrane proteins
This interactions within the membrane creates nanoscale raft domains that functions in cell signaling and membrane trafficking.
Protein-protein interactions
Gives the plasma membrane mechanical strength and restricts the diffusion of membrane proteins.
Cortical cytoskeleton
A long, thin, and flexible rod protein that
maintains the structural integrity and
shape of the plasma membrane
Spectrin
Specific type of cytoskeleton that enables the red blood cells to withstand the stress acted upon its membrane when passing through narrow capillaries.
Spectrin-based cytoskeleton
Proteins that deforms the lipid bilayer through the dynamic pushing and pulling forces exerted by the cytoskeleton or extracellular structures.
Membrane-bending proteins
During vesicle budding, cell movement, and cell division; The shape of the cell is controlled-
Dynamically
