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Concepts to understand
The flow of matter & information into and out of the cell
The "concentration gradient" concept
As in the case of a chemical reaction:
1.) _____ diffusion in the direction of ΔG < 0 (__ the gradient)
2) Equilibrium when ΔG = __
therfore [A in] = [A out ]0
Living cells sustain gradients of ___ molecules and ions.
Diffusion tends to ___ gradients.
(Equilibrium at ΔG = 0)
However, gradients are not ___ restored in cells.
Lipid bilayer is a ___ barrier.
->Large ___ molecules and ions are BLOCKED from passing through.
SIMPLE DIFFUSION
favors ___, ___ molecules
Simple diffusion is ___ (uses no energy, moves down the concentration gradient)
What molecules tend to undergo simple diffusion?
Passive/Facilitated diffusion
-Large molecules, including polar, and ions can pass through ____ proteins, such as pores (____) or channels (animals) and transporters (___ ____).
Transmembrane proteins that transport a SINGLE solute type is a ____
Passive Facilitated Diffusion
Carrier Proteins
-Solute binds on one side; ____ change occurs; then lets go on other side
-Often carry ONE type of molecule
EX: passive ___ transporter (__)
Channel Protein
-Solute moves due to ___
-When ions are transported, these channels are called ___ channels.
->They are specific to __ & __
Some channels are always open (___ channels), while others are regulated:
Example of a voltage-gated channels = opening of ___ channels
Neural signal ____ due to the opening of sodium channels.
SUMMARY So far
___ ___: no use of energy & moves along the gradient
Simple diffusion: moves ___ through the cell membrane
____ diffusion: Transmembrane proteins
____ : Transmembrane protein that transports a single solute type
Next
Active transport: use of energy & moves ____ the gradient
Membrane Potential
(___ across the membrane)
Cell is like an electric battery.
Cell is __ inside & __ outside.
Δψ : from -40 to -70 mV
ΔG = zFΔψ
z = charge
F = Faraday's constant
Δψ < 0 and F > 0 and ΔG < 0 when z __ 0
Membrane Potential is sustained by ___ /__ pumps
_ N+ out & _ K+ in with a +1 charge transfer per pump cycle
Cell generates 3 ΔG sources:
1)
2)
3)
Sodium/Potassium Pump is the example of ___ Transport
It is active, because ions move ___ their gradient (ΔG initial __ 0)
However, A LOT of ATP energy is used (ΔG ATP __ 0) so total (ΔG total __0)
Class Clicker Question
How does membrane potential, V= -70 mV, change if a significant number of Na+ channels (transporting only sodium) synchronously open?
A. will decrease, more negative
B. will increase, more positive
PRIMARY Active transport = when a ___ emergy source is used (__ or __)
SECONDARY Active Transport =
when the energy of ion ___ is used
*Primary energy source (ATP) creates the secondary energy source (__ ___).
->This energy is used to move cargo across the membrane.
Symport = two molecules move in ___ direction (move __)
Antiport =
Sodium/Calcium transporter
Two molecules move in ____ directions
This is active transport because the energy of the Na+ ___ is used.
Endocytosis = ___ large molecules and particles
Exocytosis = ___
Transduction of extracellular signals
Transduction = ___ of signal or energy from one form to another
Lateral diffusion = __ (communication)
Transverse diffusion = ___
Signal Transduction
___ = primary messenger & binds to
a receptor on the outer membrane surface
____ = on outer membrane surface
->SPECIFIC to the ligand
->Undegoes a conformational change
->SIgnal transduction
->Second messenger
->Amplification
Pathways =
Often ___ cell response
Complex interactions
G protein-coupled receptors (GPCR)
-Large family of protein receptors
-Ligand binds to receptor -> conformational change -> signal passed
Structure of GPCR = transmembrane __-___ and are couple to __ - proteins
G proteins (different types) are GTPases that ___ GTP
GTP becomes ___
Heterotrimeric G-protein:
α, β, γ subunits
α, and γ bound to the membrane
What are the signal transduction steps shown on this image?
Another example of a GPCR is the:
Adenyl Cyclase signaling pathway
Primary messengers (hormones) bind to GPCR and then G-proteins become activated and can either activate or inhibit adenyl cyclase (AC)
Second messenger = cAMP (___ the signal)
Kinase ___
Phosphatase ___
The adenyl cyclase signaling pathway
Phosphodiesterase = ___ cAMP (becomes AMP)
*It is important to be capable of turning __ the signal.
Caffeine __ the inhibitor and this results in __ signal action.
cAMP
_ cAMP molecules must bind to the regulatory sites on the inactive complex to activate the ___ subunits
->This activates protein __ __
Tyrosine Kinase Pathway
-Ligand binding causes ___
-Each kinase ___ its partner (auto___)
-Phosphorylated dimer becomes ___
Insulin receptor is an example of a tyrosine kinase receptor
-Tyrosine kinase domains catalyze phosphorylation of proteins called insulin receptor substrate (IRS) to further produce secondary messengers (PIP3).
