This document discusses membrane physiology related to protein channels, transport mechanisms, and pumps. It describes the properties and gating of protein channels, including selective permeability based on ion charge and size. It also explains active transport mechanisms like the sodium-potassium pump, which uses ATP to transport ions against their gradients. Secondary active transport is discussed where the sodium gradient provides the energy to co-transport other molecules like glucose and amino acids.
2. Properties of protein
channels
Part 1
01
Factor increase
diffusion through
protein channel
Part 02
Active transport
Part 03 Secondary active
transport
Part 04
3. →
Properties of protein channels
1) selective permeability: examples
a) Na+ channels→﹣vely charged →attract Na + more than any other ion →so it is
selective for N a+ .
b) K+ channels →smaller and uncharged →allow only smaller hydrated K+ ions
→reject bigger hydrated Na+ ions →so it is selective for K+
2) Gates of protein channels : examples
a) For Na+ channels → on outside of membrane
b) For K+ channels →on inside of membrane
4. Gating of protein channels :
“Opening and closening of protein channels is called gating “.
Two types :
1) Voltage gating :
In this gates are opened or closed due to the electrical potential changes across
cell membrane
Example are :
a) Na + gates open when inside of membrane become less negative
b) K+ gates open when inside of membrane become positive but very slow .
2) Ligand gating :
In this gate are opened and closed due to binding of another molecule with channel
protein
Example :
Acetylene choline bind with Ach channels and open it .
5. Factors increasing diffusion through protein channel
1) Temperature
2) concentration gradient
3) pressure gradient
4) permeability
Active transport :
Movement of substances across cell membrane in combination
with carrier protein against concentration gradient caused by utilisation of energy is
called active transport .
Mechanism of active transport:
Its mechanism can be illustrated by Na+
k+electrogenic pump.
6. Na+ - k+ electrogenic pump :
Transport 3Na+ ions out of cell and simultaneously transport 2K+ ions into
cell .
Function
1) Maintain z concentration difference across cell membrane.
2) Contribute to -4mV resting membrane potential -90 mV
3) Control cell volume .
Carrier protein of Na+ - k+ pump:
Has two globular proteins smaller one has unknown functions but larger
one has three functions :
a) 3 receptors for Na+ ion on inside .
b) 2 receptors for k+ ion on outside .
c) Inside potion has ATP ase activity.
7. when two k+ ions bind on the outside of carrier protein sand three Na+ ion on inside
the Passes
become activated ,liberating energy from ATP .this energy cause conformational
change in pump
expelling three Na + ion to outside and two K+ ions to inside of membrane .
Why called electrogenic ?
since Na+ - K+ pump,pumps 3 Na+out of cell and 2 K+ into cell .it creates negativity
inside cell membrane .So it is called electrogenic .
Calcium pump :
Two Ca++ pumps
One in cell membrane → pump Ca++ to outside.
other pumps Ca++ into vesicular organelles of cell .so Ca++ con in cytoplasm is
10,000time less than E.C.F.
8. TEXT HERE
TEXT HERE
TEXT HERE
TEXT HERE
TEXT HERE
TEXT HERE
TEXT HERE
TEXT HERE
Hydrogen pump :
present in :
a) Parietal cells of gastric glands
b) Late distal tubule and cortical collecting duct of kidney.
Secondary active transport :
In secondary active transport energy is not provided by ATP but it is provided by
concentration gradient of Na + ion across cell membrane .
Na +--co transport of glucose and amino acid:
carrier protein has two site outside on outside , one for Na+ and other for glucose
and amino acid when both bind concentration gradient of Na+ cause conformational
change in carrier protein glucose or amino acid co-transported with Na+
found in epithelium of GIT and renal tubules .
