Cell Membrane Transport Flashcards
What are the two types of transport in driving forces?
passive and active transport
Driving forces include ______ and ______ forces.
chemical and electrical forces
Both chemical and electrical forces =
electrochemical force
What is passive transport?
movement down the force
What is active transport?
movement against the force
Name 3 characteristics of driving forces.
- concentration gradient (ΔC): Difference in particle concentration between the inside and outside of the cell
- the gradient ”pushes” particles from higher to lower concentration areas
- force acts from higher to lower concentration areas
What is the direction of chemical driving force.
- down the chemical gradient
- from higher to lower concentration
Define ion.
a charged particle
Define cation.
particle with positive (+) charge, ex. Na+
Define anion.
particle with negative (-) charge, ex. Cl-
Define membrane potential (Vm).
a force caused by unequal distribution of anions and cations across the cell membrane
Membrane polarity (+ or -) is determined by…
net charge in the cell or intracellular reference
Charge separation =
source of energy (difference across the membrane)
Electrical driving force is measured in…
- millivolts
- represented by the …ve charge inside the cell
- ~ -70 mV (at rest)
In electrical driving force, ______ charges attract.
opposite
Direction of force in the electrical driving force depends on:
- polarity of the cell
- charge of the particle
Magnitude of force in the electrical driving force depends on:
- Strength of the membrane potential (Vm)
- Amount of charge on the particle (quality of charge, how much the ion carries)
Describe passive transport.
- spontaneous
- no cell energy is required
- downhill movement
What are the 3 types of passive transport?
- simple diffusion
- facilitated diffusion
- diffusion through channels
What is simple diffusion?
- no membrane proteins needed
- transport through lipid bilayer
What are the 6 factors affecting the rate of transport in simple diffusion?
- magnitude of the driving force
- membrane surface area
- membrane permeability
- thickness of the membrane
- lipid solubility of diffusing substance
- size and shape of diffusing particle
What is facilitated diffusion?
passive transport through a carrier
Give 4 characteristics of a carrier in facilitated diffusion.
- transmembrane protein
- binding sites: specific
- bind one at a time
- random conformational changes
What are the 3 factors affecting the rate of transport in facilitated diffusion?
- rate of transport of the carrier
- number of carriers
- concentration gradient
Where is GLUT4 synthesized?
rough ER
Where is GLUT4 packaged?
vesicles
_____ and _____ stimulates GLUT4 insertion.
insulin and exercise
What happens with diabetes?
- lack of insulin action means less GLUT4
- decrease glucose uptake
- increase glucose in blood
What is the increase of GLUT4 insertion with exercise called?
primary exercise effect
What does exercise do to GLUT4 activity?
- increase (intrinsic)
- secondary effect
- technological limitations
What kind of process is diffusion through channels?
passive
Name 3 characteristics of diffusion through channels.
- transmembrane protein
- passageway or pore
- substance specific
What are the 2 types of channels?
- aquaporins
- ion channels
Describe aquaporins.
- H20
- Diffusion
- selective pores that permit water movement by diffusion
What are the 2 parts of ion channels? Describe ion channels.
- leak channels and grated channels
- bidirectional: allows movement of ions in both directions
Describe leak channels.
allow Na+ and K+ to move down concentration gradients to maintain stable resting membrane potential
Describe grated channels.
chemical messenger binds, then channel allows ion through
Rate of transport in ion channels depends on what 3 things?
- transport rate of each channel
- number of channels
- open or closed state
