lecture 1 Flashcards
The cell membrane is a highly selective filter that:
ØActively maintains unequal concentrations of ions across it
ØServes as a filter that allows nutrients to enter and waste to leave the cell
ØActively maintains unequal concentrations of ions across it
ØServes as a filter that allows nutrients to enter and waste to leave the cell
the cell membrane has two main components
- phospholipid billyer
- proteins
______________ most abundant; have glycerine backbone;
amphipathic molecules -have a polar, hydrophilic head; and two
non-polar, hydrophobic tails, e.g. phosphatidyl choline
a. Phosphoglycerides:
what lipids make up the membrane
a. Phosphoglycerides:
b) Sphingolipids
c) Sterols
__________–have a sphingosine backbone; amphipathic molecule,
e.g. sphingomyelin
b) Sphingolipids
_______________–non-polar, e.g. cholesterol
c) Sterols
The membrane is impermeable to ions. ____________ allow the passage of
ions through the membrane.
Proteins
____________– catalyze reactions
a) enzymes
_______________________ - for hormones, etc.
b) receptor molecules
________________s – allow entry/exit of substances through
the membrane
c) passive channels/pores
____________________ – active transport across the membrane
d) pumps
_______________– passive transport: the protein binds the ion and
transports it by diffusion or rotates to flip the ion to the other side of
the membrane
e) carriers
Membranes divide cells into physically separate compartments,
which allows:
1) Control of solute concentrations
2) Storage of energy to do work
1) chemical energy – by establishing concentration or
electrochemical gradients
2) electrical energy – by establishing charge separatio
_______________ – by establishing concentration or
electrochemical gradients
1) chemical energy
________________– by establishing charge separatio
2) electrical energy
-permeation of solutes across a barrier
Passive Diffusion
Fick’s Law of Diffusion: dS/dt = Px(C1-C2)
depends on how soluble a solute is in the membrane – non-polar
substances have a greater Px than polar substances, thus they are MORE
permeable
Permeability Constant
Px
- the Neuron Doctrine: the nervous system is made up of discreet signaling elements (neurons)
1) Santiago Ramón y Cajal (Spain)
-discovered and developed histological staining techniques –cells are
impregnated with silver grains (Golgi stain)
2) Camillo Golgi (Italy)
The brain exhibits three principle types of behavior:
1) Sensory
2) Movement
3) Cognitive
- All are based on electrical processes
The membrane itself has a very high ______________ – channels may be considered
as variable resistors61 in the membrane
resistance
Channel types:
1) Open Channels (or Leakage Channels)
2) Gated Channels
types of Gated Channels
1) Voltage-gated
2) Ligand-gated
3) Stretch-activated or mechanosensory (MS)
Active transport
Ø Requires ATP for energy
Ø Active in absorption/secretion and maintaining
Vm
Ø Pumps 3Na+ (out):2K+ (in)
Performed by “pumps” which require energy e.g.
Na+K+-ATPase (Na+-K+ Pump)
_______________
Ø Requires ATP for energy
Ø Active in absorption/secretion and maintaining
Vm
Ø Pumps 3Na+ (out):2K+ (in)
Active transport
Blocked by cardiac glycosides:
1) From dried leaves of foxglove plant-digitalis
2) From Strophanthus plant-ouabain
3) CGs found in venom of certain toads
Cell membrane is_____________e (this means at rest, it is mostly
permeable ______________
selectively-permeable
to potassium)
Remember, membrane potential is measured as the difference in voltage across the
membrane - that is, it is ____________where the outside is conventionally taken to be at __________________
the potential of the inside of the cell relative to the outside (typically
Vm= -70 mV)
(0 V)
Ionic concentrations in ______________ for a typical mammalian muscle cell:
(mM)
______________ takes into account the permeability of the membrane to. more than one moncovalent ion. For only one permeable ion, it reduces to the Nernst equation
Goldman equation
_____________ is when KCL is equal on either side of the SPM, the net ionic flow=0
Donnan equalibrium
