biological kinetics/transport (midterm 1) - equations should be studied too Flashcards
what initiates signaling for ligand and receptor binding kinetics
ligand binding to a membrane bound receptor
where is there an equilibrium between
free ligand, free receptor, and ligand-receptor complex
what is the cell membrane
thin film of non-covalently bound lipids (bilayer) and proteins, allowing free movement of molecules
what are lipids composed of that make them amphiphilic
hydrophilic head (water soluble) and hydrophobic tails (lipid soluble), which form the lipid bilayer together
what molecules struggle to cross the lipid bilayer of the cell membrane
larger, hydrophilic molecules
how can the struggling molecules pass through the membrane
using protein channels
what molecules go down the concentration gradient by passive diffusion
hydrophobic molecules (small) - oxygen, CO2, nitrogen
what cannot transit across the lipid bilayer
large, neutral, polar molecules (like glucose) and charged molecules (ion - Na+, K+, Ca++)
what does the cell membrane do for the extracellular environment
maintains ionic and chemical differences between the extracellular environment and the cell’s cytosol
what are lipids composed of
choline, phosphate, glycerol (head), fatty acid tails
how can transport be accomplished
diffusion (simple or facilitated) or active transport (requires energy)
what does diffusion speed depend on
molecular/pore diameter
what is the charge of sodium channels
strongly negatively charged, allowing dehydrated sodium ions to pass through the membrane
what is the charge of potassium channels
uncharged, allowing hydrated potassium to pass, but preventing larger hydrated sodium to pass through
what is bulk flow
solute diffusion
when does diffusion dominate
when the Peclet number is less than 1
when does bulk flow dominate
when the Peclet number is greater than 1
what are voltage gated channels
the molecular conformation of the protein channel changes in response to the electrical potential across the cell membrane
what causes a voltage gated channel to open/close
a strong negative, intracellular charge = closed
loss of this charge = open
“all or none” response
what are chemical gated channels
the molecular conformation of the protein channel changes in response to ligand binding
what is a patch-clamp technique
ion current flow through protein channels where a micropipette is brought into contact with a single cell, then small suction force is applied to the other end of the micropipette, sealing the cell membrane to the tip
what is facilitated diffusion
diffusion of solute through a gate which opens/closes randomly due to thermal energy (Brownian motion)
what type of diffusion does glucose and amino acids use
facilitated diffusion because glucose has to enter the cytoplasm for metabolism, but can’t diffuse on its own
what is the concentration of water in cells controlled by
the relative amount of molecules on either side of the selectively permeable cell membrane
