Membrane Structure Flashcards
What are five functions of the cell?
Cell metabolism, energy use, synthesis of molecules, communication, reproduction/inheritance
What is membrane potential?
The difference in charge across the membrane
Is the outside of the membrane positively or negatively charged relative to the inside?
Outside positive relative to inside
Glycocalyx
Carbohydrates, glycolipids, and glycoproteins combined on outer cell surface
Transmembrane Protein Functions
Transport, reception, facilitates signaling
What are three membrane lipids?
phosphoglycerides, sphingolipids, cholesterol
What are the four main types/functions of membrane proteins?
adhesion, receptors, transporters, pores
How thick is the lipid bilayer?
3-5 nm
What interactions contribute to the stability of the lipid bilayer?
Hydrophobic interactions of lipophillic tails, van der Waals interactions between lipophillic chains
Where are sphingolipids commonly found?
CNS (central nervous system) molecules
What are some factors that increase fluidity of the membrane?
Degree of saturation (more double bonds makes kinks in nonpolar tails, which decreases the van der Waals reactions and decreases the surface area of tails touching) and Less Cholesterol (less interactions with tails, more fluidity)
What are some factors that decrease membrane fluidity?
Longer nonpolar C-C chains (stronger interactions), More Cholesterol (more interactions, more rigid membrane)
What is the purpose of lipid rafts?
Facilitate communication between inside and outside of cell
What do flippases do?
Participate in rearrangement of membrane composition (“flip” back and forth)
Integral proteins
extend deep into membrane, usually go all the way through, can form channels
Peripheral proteins
attach to integral proteins on either the inside or outside of cell bilayer
Why do integral proteins have both hydrophillic and hydrophobic domains?
So the protein can interact with all parts of the membrane and stay in a fixed position
How are lipid anchored proteins bound to the lipid?
With covalent bonds
What are marker molecules?
allow cells to identify each other (necessary b/c only one type of peptide bond), examples are glycoproteins and glycolipids bound to protein, as well as carbohydrate chains
These proteins are secreted and loosely associated with cells and extracellular matrix
proteoglycans
What are the functions of glycoproteins?
Protection, immunity, transplant compatibility, structural integrity and adhesion, fertilization, development
These attachment proteins attach cells to other cells
cadherins
Integrins
Integral proteins that attach to extracellular molecules (sometimes allow communication), link cytoskeleton to extracellular matrix, cluster to form focal adhesions
Tight junctions
seal neighboring cells together to prevent molecules from leaking between them
Adherens junctions
join actin bundles in neighboring cells together
Desmosomes
join intermediate filaments in neighboring cells together
Gap junctions
allows small water-soluble ions and molecules to pass from cell to cell
Hemidesmosomes
anchors cell to the basal lamina
In transport proteins, does the hydrophobic or hydrophillic region faces inward (toward the channel)
Hydrophillic
These channels are always open and keep the plasma membrane permeable when the membrane at rest
nongated ion channels
These channels are opened and closed by certain stimuli
gated ion channels
What are the three forms of carrier proteins (transporters)?
uniporters (move one particle), symporters (move two particles in same direction at same time), antiporters (move two particles in opposite directions at same time)
For ATP-powered transport proteins, the rate of transport depends on which two factors?
the concentration of the substrate and the concentration of ATP
Receptor proteins serve what main purpose?
an intercellular communication system
What is the difference between channel proteins and carrier proteins?
Carrier proteins have binding sites and must change shape to transport substances, while channel proteins just provide a passageway for substances
They act to catalyze reactions at outer/inner surface of the plasma membrane
Enzymes
