Plasma Membrane Structure Flashcards
How do cells closely regulate what enters them and what they secrete?
Plasma membrane
Biological membranes are 2-dimensional, fluid structures within which lipid and protein molecules diffuse freely. Term that commonly describes the plasma membrane.
Fluid mosaic model
Which part of the plasma membrane is hydrophobic and hydrophilic?
Hydrophobic tails
Hydrophilic heads- interact with aqueous intracellular and extracellular surroundings
Knowing the structure of the plasma membrane which molecules can diffuse easily and which ones would require help?
Small and non polar molecules can diffuse easily.
Large and polar molecules require help
What are the main structure of plasma membrane?
- Lipids
2. Functional Proteins
Three main classes of lipids
- Phospholipids
- Sterols
- Glycolipids
What is the predominant component of the lipid bilayer? Responsible for insideness and outsideness of the plasma membrane.
Phospholipid
The phospholipid is amphipathic which means?
It has a polar head (ex. Phosphate-negatively charged)and non polar tail (alkanes-non polar)
Therefore, they have very different behavior
What is the second main lipid component of the plasma membrane? Give an example of this lipid.
Sterol- ex. Cholesterol
Modulates fluidity of plasma membranes and has a characteristic four-ring structure
Cholesterol
Similar to phospholipid but with carbohydrate instead of phosphate group in one end
Glycolipid
Sphingomyelin tends to cluster with cholesterol molecules to form what structures?
Lipid rafts
Glycolipids can have what two backbones?
Glycerol and sphingosine
Glycolipids are involved in what two processes?
Cell signaling and adhesion
Proteins that are actually embedded within the plasma membrane
Integral proteins- most are transmembrane proteins
Transmembrane protein domains
Hydrophilic cytosolic domain, hydrophobic domain, hydrophilic extracellular domain
Examples of transmembrane proteins
Proton pumps, ion channels, and G-protein coupled receptors
These proteins are covalently bound to single or multiple lipid molecules that anchor the protein within the membrane without the protein contacting the membrane.
Lipid-anchored
Example of lipid-anchored proteins
G proteins- intracellular membrane-bound structures that help coordinate the signaling cascade initiated by the G protein-coupled receptors.
These proteins are found within the cytoplasm and are temporarily attached to integral proteins or are associated with peripheral regions of the lipid bilayer.
Peripheral proteins
These proteins tend to interact with biological membrane only temporarily before resuming their functions pan within the cytoplasm. This category includes some enzymes and hormones
Peripheral Proteins
Proteins can be glycosylated which refers to the addition of what chains to a peptide chain?
Oligosaccharide
Example of glycoproteins or glycosylated proteins that is relevant to the plasma membrane
- Major Histocompatibility complex
2. The antigens involved in the ABO blood type system
Membrane glycoproteins are often involved in what processes?
Cell recognition and communication
Lipid bilayer enclosing a spherical space. These laboratory-derived structures are used by researchers to deliver material to target cells and to test cell membrane permeability.
Liposomes or lipid vesicles
An aggregate composed of a single layer of lipids in aqueous solution, where the hydrophilic head is in contact with the solvent while the hydrophobic tail region is sequestered in the center.
Micelle
Can reduce the surface tension of a solution
Surfactants
What kind of biologically relevant molecule is formed through an esterification reaction
Phospholipids
T or F. Amphipathic molecules can be used as surfactants to reduce solution surface tension
True.
T or F. Liposomes are lipid bio layers and micelles are lipid monolayers, both of which contain membrane proteins.
False. Micelles do not contain membrane proteins, only liposomes do.
Move phospholipids from the inner leaflet to the outer leaflet
Floppases
Move phospholipids from the outer leaflet to the inner leaflet
Flippases
Enzymes responsible for bidirectional movement of gathering phospholipids
Vertical translation
Scramblase
The degree to which phospholipids can move around laterally
Membrane fluidity
Lower temperature equals more or lower fluidity?
Lower fluidity like how butter is more solid at lower temp
What molecule is the mediator of membrane fluidity and prevents it from going to extremes?
Cholesterol
- Promotes membrane fluidity at colder temp
- Tripping the phospholipids at higher temp- reduces membrane fluidity
Saturated vs. Unsaturated
No carbon-carbon double bonds- very linear and regular
Saturated
Saturated vs Unsaturated
Contain at least one double bond and very often more- cis conformations cause it to be a lot less linea
Unsaturated
Saturated characteristics
Very stackable- all linear
High melting point
Makes membrane less fluid
Unsaturated characteristics
Less stackable
Lower melting points
Makes plasma membranes more fluid
T or F. Glycoglycerolipids and sphingolipids differ from each other in the type of carbohydrate group attached
False. They differ from each other in their backbone molecule
