Membrane Transport
Lecture 21
Chapter 12
If one makes a pure lipid
membrane;
1) It would be biologically
inert
2) Many molecules could
not transverse to the
other side
If one add the right
proteins to it;
1) It would be biologically
active
2) Many molecules could
transverse to the other
side
12_01_transport_prot.jpg
Can I get
through
please?
YES
12_02_diffusion_rate.jpg
Depends…
Who are you?
How big are
you?
Are you
charged?
YES
NO
NO
If I cannot get diffuse across, can you help?
12_03_carrier_channel.jpg
YES - but only if you fit through the right protein turnstile!
The carrier protein actually
changes shape to allow the
passage of the solute
The channel protein
discriminates on what is
allowed through!
Does the system spend energy or not to move things?
Depends on the type of transport!!!
12_04_pass_act_transport.jpg
All happen freely - by
diffusion (simple or mediated)
Energy needed normally ATP
Where there's a membrane there are transporters - true for
all living membranes!
12_05_carrier_proteins.jpg
A complex Ca pump - uses energy to power the pumping
of JUST Ca ions from one side of the membrane to the
other.
12_06_Ca_pump.jpg
In this example, there is a channel inside the protein
which open up
The situation can get a little more complex - here we see that
the protein is acting in a slightly more complicated manner.
In this example, the protein physically has to change shape
each time it pumps material
12_07_conforma_change.jpg
Two forces may be at work in passive transport - if we are
dealing with a charged solute across the membrane.
12_08_electroch_gradient .jpg
1) CONCENTRATION
2) MEMBRANE POTENTIAL
How many ways to power active transport 1) not just with ATP - which is the most utilized
2) Also by coupling to another solute with concentration gradient
3) Photon energy from light
12_09_active_transport.jpg
The sodium-potassium pump
- very important in animal cells
12_10_Na_K_pump.jpg
Its job is to keep both ions at different concentrations on either
Side of the membrane
This is how it cycles -
12_12_Na_K_cyclic.jpg
Remember me!
Types of carrier proteins - 3 types exist
12_13_Carrier_proteins.jpg
This is how the symport version works - all based on affinity
of binding and conformational changes
12_14_symport.jpg
The same cell may employ different carrier proteins at different
points to perform is tasks.
12_15_glucose_gut.jpg
Revision of Osmosis - diffusion of _________?
12_16_osmosis.jpg
Too much pressure and the membrane will rupture!
Different classes of organisms use different tactics to avoid
rupture…
12_17_osmotic_swelling.jpg
Animal vs Plant cells
12_18_solute_transport.jpg
Carrier proteins are highly selective due to internal shape and
charge
12_19_selectivity_filter.jpg
Ion channels exist in alternative states - open and closed
12_20_ion channel.jpg
Nature has different ways to open and close these channels
12_24_Gated _ion_chan .jpg
Membrane Potential = differences in total charge
12_27_membr.potential.jpg
A nerve impulse uses channel proteins and lots of them..
12_30_neuron .jpg
12_33_3_conformations.jpg
12_34_Ion_flows.jpg
12_38_act_potential_propg_p
art2.jpg
12_40_nerve_terminal.jpg
12_41_ion_channel_synp.jpg
12_43_excitatory_inhib.jpg