Cell Membrane, Membrane Transport, and Membrane Potential 2 Flashcards
What is the role of transport proteins?
move hydrophilic substances across the plasma membrane
-allow things unable to cross the membrane by themselves to cross
What are the three types of transport proteins?
channels
carriers
active transporters
What are channels?
transmembrane proteins with a 3D shape that forms a tiny fluid filled pore connecting ECF and cytoplasm
What is able to cross through channels?
ions
What is the function membrane channels?
facilitated diffusion of ions into and out of the cells
(passive and does not require energy)
Are channels specific?
they can be
-Ca2+ channels, Na+ channels, Cl- channels
Are channels saturable?
no
What are open channels?
channels that are always open and ions freely flow through facilitated diffusion
-creates “leak currents”
What are gated channels?
spend most of their time in the closed state, and will open only when stimulated
What are the three types of gated channels?
chemically gated, mechanically gated, and voltage gated
What is allosteric modulation?”
changing something with noncovalent binding
What is covalent modulation?
changing something with covalent binding
What are ligand gated channels?
channels that have a ligand that binds without covalent binding and changes confirmation
What are phosphorylated gated channels?
channels that open when they are phosphorylated with a covalent bond
What causes voltage gated channels to open?
change in membrane potential
What causes pressure gated channels to open?
stretching of the membrane
What are carriers?
transmembrane proteins that move hydrophilic building blocks across the membrane via facilitated diffusion
Are carriers open on both sides of the membrane?
no
-if there were open on both sides it would hurt the integrity of the membrane and allow all things to cross without any control
What is the process of carriers working?
-molecule that needs to be transported enters one side of the carrier and binds to a specific spot
-transition state causes both sides of the carrier to be closed
-the other side of the carrier opens and allows the molecule the exit through the other side of the membrane
What are active transporters?
transmembrane protein that moves ions and hydrophilic building blocks across the plasma membrane via active transport
What is active transport?
moving of molecules against the concentration gradient
What are structural proteins?
forms cell to cell attachments that hold adjacent epithelial cells together
What are tight junctions?
cell to cell junctions that prevent intercellular movement of fluid and dissolved substances
What are desmosomes?
structural support that does not restrict intercellular movement
-just maintains the cells integrity so the cells do not come apart
What are gap junctions?
two ion channels on adjacent cells that create a channel between two cells
-allows for ions to flow between cells
-allow for rapid cell to cell communication
What are enzymes?
integral, transmembrane, or peripheral membrane proteins that catalyze specific chemical reactions either on the extracellular surface of cell or inside cell
What are the steps of enzyme function in the cell membrane?
-ligand binds noncovalently
-transmembrane protein changes shape
-the change in shape causes a change in function
How long does it take for a protein to be made?
2 hours
Because it takes so long to make a protein, what happens?
many proteins are synthesized in advance and stored in an inactive form, activated when they are needed
What does the interaction between substance and protein binding site follow?
the mass action model
Where are carbohydrates attached to the membrane?
on the extracellular surface
What are proteins with carbohydrates bound called?
glycoproteins
What are lipids with carbohydrates bound called?
glycolipids
What is the sugar coating of the cell membrane called?
glycocalyx
Why is the glycocalyx important?
plays important role in enabling cells to identify and interact with each other
What are four characteristics of membrane structure?
selectively permeable barrier, mosaic, dynamic, and fluid
What substances are higher in the extracellular fluid?
-Na+
-Ca++
-Cl-
-HCO3-
-glucose
What substances are higher in the intracellular fluid?
-K+
-Mg++
-phosphates
-pH
-proteins
What is passive transport?
movement across the membrane that does not require energy
-down gradient (concentration, pressure, and electrical)
What are the types of passive transport?
diffusion
osmosis
bulk flow
What is active transport?
movement across the membrane that does require energy
-against concentration gradients
What are the types of active transport?
active transporters and bulk transport
What is random thermal motion?
molecules in a fluid are continuously and randomly bouncing around
What is the rate of movement directly related to?
temperature
What is the rate of movement inversely related to?
mass
What is diffusion?
movement of stances other than water down a gradient
When does net movement of diffusion stop?
at equilibrium
What does passive transport move toward?
equilibrium
What is the driving force of diffusion?
gradient
What alters the flow of diffusion?
membrane resistance
If a membrane has high permeability what is the net flux?
there is a high net flux
