Cell-signaling, allow things to pass and exit. Semi-permiable.
What is the extracellular environment?
outside the cell
What is the cytosol enviroment?
Inside the cell
What is the main body of the plasma membrane made of?
What are the protein recognitions sites on the Plasma membrane?
This protein spans all the way through the membrane from one side to the other.
Integral Membrane Protein
Phospholipids are amphipathic molecules. What does that mean?
It has both Mydrophboic and hydrophilic parts
The two leaflets of the plasma memb. are?
What are the two types of Integral or intrinsic membrane proteins?
Transmembrane proteins and Lipid-anchored proteins.
These proteins have regions that are physically embedded in the hydrophobic portion of the phopholipid bilayer
For these proteins an amino acid of the protein is covalently attached to a lipid.
These proteins are noncovalently bound either to integral membrane proteins that project out from the membrande or to a polar head groups of phospholipids.
Peripheral or extrinsic membrane proteins
Approx how many of all genes encode transmembrane proteins?
Plasma membrane are important for ?
Medical and biological studies
These can be used to predict the number if transmembrane proteins.
Is the trend of 20-30% gene encoding true for all facets of life?
How do you view the plasma membranes?
With a Transmission Electron Microscope or freesz fracture electron microscopy
The sample is thin sectioned and stained with heavey metal dyes. These dyes bind tightly to the polar head groups but not the fatty acyl chains. This makes the membranes resemble railroad tracks
Transmission electron microscopy (TEM)
specialized form of TEM used to analyze the interior of the phospholipid bilayer. Samples frozen in liquid N and fracurted w/ a knife. the leaflets fracture into the P face (inside) and the Eface (outside). can provide significant details about the membrane protein
Freeze Fracture Electron Microscopy (FFEM)
Most lipids can rotate freely around their long axes and move laterally within the membrane leaflet, thus membranes are concidered?
But flip-flop of lipids from one leaflet to the opposite leaflet does not occur spontaneously. what is needed to move the lipids
What does flippase require to move lipids?
Certain lipids associate strongly w/ eacgother to form what?
These lipid rafts have some differences than the rest of the membrane.
Have a high concentration of cholesterol and unique set of membrane proteins
What are the factors that effect fluidity of te plasma membrane?
Length of fatty acyl tails, presence of double bonds, and the presence of cholesterol
How does the length of fatty acyl tails effect fluidity?
shorter tails are less likely to interact which makes it less fluid like
how does the presence of double bonds effect the fluidity of plasma membranes.
The double bonds creat kinks in the fatty acyl tail, making it more difficult for neighboring tails to interact.
How does the presence of cholesterol make the membrane less fluid like?
It stabilizes the membranes but is effected by temp.
What ass the name of the experiments on lateral movements done in 1970?
Larry Frye and Michael Edidin experiment.
Not all integral membrane proteins can move. depending on the cell tupe what percent are restricked in their movement?
What are the Integral membrane proteins may be bound to that restrict proteins from moving laterally.
Membrane proteins may be also attached to molecules that are outside the cell, such as the interconnected network of proteins that forms the
In Eukaryotes what systems work together to synthesize lipids?
Cytosol and endomembrane
These are made via enzymes in cytosol or taken into cells from food.
Fatty acid building blocks
Where does the processing of the fatty acid process occur?
At cystosolic leaflet of the Smooth ER
How are lipids transfed?
How do the lipids in the ER diffuse to the nuclear envelope?
They diffuse laterally
Where are lipids transpoted?
To the Golgi, lysosomes, vacuoles, or plasma membrane
these extract lipid from one membrane for insertion in another.
Lipid exchange proteins.
Except for proteins destined for semiautonomous organelles, most transmembrane proteins are directed to?
the ER membrane 1st
From the ER, membrane proteins can be transferred via _____ to other membranes of the cell
This is the process of covalently attaching carbohydrate to a protein or lipid.
Carbohydrate to lipid
Carbohydrate to protein
These can serve as a recognition signals for other cellular proteins. Play a role in cell surface recognition and helps protect proteins from damage
These are Glycosylation that have an attachment of carbohydrate to nitrogen atom of asparagine side chain
These are glycosylation that have addition of sugars to O2 atom of serine or threonine side chains. Occurs only in Golgi
Since the membrane is selectively poermeable only some ions and molecules can pass through. This ensures that?
Essential molecules enter, Metabolic intermediates remain, and waste products exit
What are the ways to move across the membranes?
Passive and Active Transport
Passive Transport can be broken down into two types:
Passive diffusion and facilitated diffusion
No energy: Diffusion of solute through a membrane w/o transport protein
No energy: Diffusion of a solute through a membrane w/ the aide of a transport protein.
This requires energy - up or gainst gradient.
Barrier to hydrophilic molecules and ions due to
Rate of diffusion depends on?
Chemistry of solute and its concentration
Diethylurea diffuses______ faster through the bilayer than urea, due to nonpolar ethyl groups
Living cells maintain a relatively constant internal environment different from their external environment. What are the two types?
Transmembrane gradient and ion electochemical gradient
Equal water and solute concentrations on either side of the membrane
Solute concentration is higher (and water concentration lower) on one side of the membrane
Solute concentration is lower (and water concentration higher) on one side of the membrane
Water diffuses through a membrane from an area with more water to an area with less water
If the solutes cannot move, water movement can make the cell ____ as water enters or leaves the cell.
Shrink or swell
the tendency for water to move into any cell
How do cells maintain their size and shape?
Maitianing balance between extracellular and intracellular solute concentrations
shrinkage of a cell in a hypertonic solution
swelling and bursting of a cell in a hypotonic solution
What prevents mahjor changes in cell size?
pushes plasma membrane against cell wall
plants wilting because water leaves plant cells
Freshwater protists like Paramecium have to survive in a strongly hypotonic environmene. To prevent osmotic lysis, _______ take up water and discharge it outside the cell