-
How do channel and carrier proteins differ?
- –Channel proteins
- •Select solutes based on size and
- electric charge
- –Most of the smaller channels
- transport ions
- –Some are larger and less specific
- •Continuous passage when open
- •Passive transport only
- –Carrier proteins (aka
- transporters or permeases)
- •Select specific solutes at
- binding sites, undergo conformational change after binding
- •Slower
- •Exhibit saturation kinetics
- •Subject to competitive inhibition
- •Passive and active transport
-
How do passive and active transport differ?
- •Passive transport
- –Down a concentration or
- electrochemical gradient (from a region of higher to lower free energy)
- –Moves toward equilibrium
- –No energy input
- •Active transport
- –Against a gradient
- Requires energy
-
Of the four different transport mechanisms discussed,
which ones are examples of passive transport and which ones are examples of
active transport?
-
Which transport mechanism(s) utilize carrier
proteins? Which one(s) utilize channel proteins?
- facilitated diffusion requires- carrier and
- channel proteins.
- Active transport uses carrier proteins
-
Understand all four transport mechanisms.
-
How do the following molecules get through the
cell membrane (simple diffusion, facilitated diffusion, active transport,
or two of these mechanisms): water, glycerol, O2, CO2,
glucose, amino acids, ions, oils, ethanol, steroids?
- simple diffusion- H2O, glycerol, small nonpolar (O2, and CO2), large nonpolar (oils, steroids)
- facilitated diffusion- glucose, water, ions,glycerol, animo acids
- active transport- glucose, ions
-
What are some factors that affect the rate of
diffusion and how (directly or inversely proportional)?
- –Concentration gradient
- –Surface area (of the membrane)
- –Temperature
- –Solubility (in phospholipid bilayer)
- •Polarity of particle
- •Charge of the particle
- –Size of particle
- –Distance (membrane thickness)
-
Know the meaning of semipermeable or selectively permeable, osmosis, hypotonic,
hypertonic, and isotonic.
- semipermeable- certain types of molecules can get through
- osmosis-is diffusion of water
- across a selectively permeable membrane.
- Water will move
- toward the region with higher impermeable solute concentration.
- hypertonic- higher concentration of solutes outside the cell
- hypotonic- lower concentration of solutes outside the cell
- isotonic- equal concentration
-
-
Understand Table 8-1. For example, how do the
kinetic properties of carrier-mediated transport differ from that of simple
diffusion
facilitated diffusion requires membrane protein, saturation kinetics, competitive inhibition
-
-
What are uniport, symport, and antiport?
-
What type of transport proteins are
transporters? Permeases? Porins? And aquaporin?
- -Facilitated diffusion
- •Transport protein allows movement of solute
- –Carrier Proteins (Transporters, Permeases)
- –-Channel Proteins
- –Porins
- •Larger pores and less specific
- •Allow passage of various
- hydrophilic solutes
- •Transmembrane segment is a β barrel
- –Aquaporins
- •Facilitate rapid movement of
- water into and out of cells
-
How does glucose transporter GLUT1 work?
- Can transport in
- either direction
- [Glucose] is kept low
- inside the cell because incoming glucose gets phosphorylated to glucose-6-phosphate
-
Is this transport an example of simple diffusion,
facilitated diffusion, or active transport?
facilitated diffusion
-
Does this transport utilize carrier proteins or
channel proteins?
carrier protein
-
Can this transport occur in either direction or
is it unidirectional?
either
-
What is achieved when the transported glucose
gets phosphorylated immediately upon entering the cell?
The concentration of glucose is kept low
-
How does chloride bicarbonate exchanger work? Is
this transport an example of simple diffusion, facilitated diffusion, or active
transport?
- facilitated, antiport
-
Does this transport utilize carrier proteins or
channel proteins?
channel proteins
-
In which direction does it move Cl-
and HCO3- in the capillaries in the muscle?
- HCO3- moves outside
- Cl- moves in
-
In which direction does it move Cl-
and HCO3- in the capillaries in the lungs?
- HCO3- moves in the cell
- Cl- moves out
-
Be able to explain why the direction is reversed
in these two locations of the body. Understand Fig. 8-3
because the blood plasma in lungs has higher o2 and low co2
its the opposite in other tissue
-
What are the three types of transmembrane channel
proteins? What type of molecule does each transport?
- –Ion channels
- •Form narrow aqueous pores lined
- by polar groups
- •Most are selective ion channels
- (by size and charge), some only allow a single type of ion to pass through.
- •Rapid rate of transport
- –Porins
- •Larger pores and less specific
- •Allow passage of various
- hydrophilic solutes
- •Transmembrane segment is a β barrel
- –Aquaporins
- •Facilitate rapid movement of
- water into and out of cells
-
How do leak
ion channels and gated ion channels differ?
- –While a few channel proteins are
- “leak channels” (i.e.: generally open), most are “gated channels”.
- –Gated channels spend more time in
- open state when stimuli are present.
- •Voltage-gated
- •Ligand-gated
- •Mechanically-gated
-
What are the three types of gated ion channels
and what kind of stimuli will activate their opening?
-
What are “pumps”? What are coupled transporters?
pumps are direct/active transport that use ATP hydrolysis directly
- coupled- indirect/secondary active transport
- –Simultaneous transport of two solutes (one down its gradient
- and one up its gradient)
-
There are three types of active transport that
differ in their driving force, what are they?
Na+/K+ ATPase pump -ATP hydrolysis
- Na+/Glucose Symporter-Simultaneous
- transport of two solutes (one down its gradient and one up its gradient
H+ ATPase pump -they use light
-
How does Na+/K+ ATPase
work? How many Na+ and K+ ions does it transport in
each cycle and in which direction? Is this transport an example of primary/direct
active transport, secondary/indirect active transport, or light-driven
active transport?
- uses ATP to transfer each ion against its gradient. 2 k+ in and 3 Na+ out.
- pump k in
- primary/direct
-
The electrochemical gradient of which ion is
often used to drive the secondary active transport of solutes across the
animal cell plasma membrane? How about for the plant, fungal, and
bacterial cells?
K+, H+
-
How does Na+/glucose symporter work?
Is this transport an example of facilitated diffusion, primary/direct
active transport, secondary/indirect active transport, or light-driven
active transport?
- seconday/indirect active transport
-
Know all three transport proteins in slide 34.
What solutes do they transport and in which direction? On which domain (apical
or basolateral) of the intestinal epithelial cell is each found? For what
purposes do they serve at these locations?
-
How does bacteriorhodopsin work? How is this
transport proteins embedded in the cell membrane?
light driven photon pump,7 transmembrane alpha helices
-
What roles does Na+/K+
ATPase play in the cell?
- –Maintains appropriate
- intracellular concentrations of Na+ and K+ ions
- •High extracellular [Na+] serves as driving force
- for the uptake of sugars and amino acids
- –Maintains membrane potential
- –Maintains osmotic balance and
- regulates cell volume
|
|
