Biological Membranes and transport ions and pores Flashcards
What types of movement can membrane proteins do?
Conformational change
Rotation
Lateral diffusion
How does temperature affect membrane fluidity?
As temp increases membrane fluidity increases due to increased kinetic energy
What are integral proteins?
Embedded within the phospholipid bilayer
Referred to as transmembranous
Extensive hydrophobic domain which interacts with the hydrophobic tails
What are peripheral proteins
Bound to the surface of the membrane via electrostatic and hydrogen bonds
Can become dissiociated with the membrane by pH disturbances
What can pass readily through the lipid bilayer?
Small uncharged molecules and polar and hydrophobic
What is the difference between simple diffuse and facilitated diffusion?
Simple diffusion isn’t saturated, due to a limited number of channels in the membrane facilitated diffusion will reach a max rate eventually
What are ligand gated channels
Open and close when a chemical signalling molecule binds to it
What are voltage gate channels
Open in response to changes in membrane potential
What are mechanically gated channels
Open in response to mechanical stretch of the membrane- mechaoreceptors in skin
What is primary active transport?
Where energy is derived directly from ATP hydrolysis
What is secondary active transport
Known as co transport
Utilises energy from a. Pre-existing electrochemical gradient
What are symports? Ant ports?
Where the ions/ molecules flow through the transporter in the same directions
Where they flow in opposite directions
What is the Na+/H+ exchanger
It is an acid extruder which alkalinises the cell.
It uses a pre-existing Na+ gradient to move sodium into the cell and hydrogen out of the cel.
Important in the kidney tubule where it can be targeted by amiloride. DIURETIC
What is the Na+/HCO3- co-transporter?
Causes alkali influx and therefore alkanisises the cell
Uses pre-existing Na+ gradient to move both 1Na+ and 3 HCO3- into the cell
What is the anion exchanger
Aka band 3
Alkali extruder acidifies the cell
Moves 1Cl- in and 1 HCO3- out
Found on erythrocytes and kidney tubules
Which transporter is responsible for extruding the majority of Ca2+ after a rise in intracellular calcium?
The Na+/Ca2+ exchanger
Moves 3Na+ into the cell for every 1 Ca2+ out
It has a low affinity but a high capacity
What does the value of delta G tell us?
Whether the transport is passive or active
Negative- passive
Positive- active
Distribution of water
2/3 intracellular
1/3 extracellular
Of that 25%- plasma
75%-interstitual fluid
What is the concentration of sodium inside and outside the cell?
Inside- 12mM
Ouside - 145mM
Conc of chloride ions
123mM out
4.2mM in
Conc of calcium
1.5mM out
10 to the power -7 in
Conc of potassium
140mM inside
4.5 mM out
What is isotonic
Equal solute equal water
What is osmole
Measure of solutions ability to create osmotic pressure and this affect the movement of water
Proportional to the number of osmotic particles in solution
What is osmolality
When the concentration of a solution is expressed in osmoles per kg of water
Osmolar concentration of a solution is referred to as osmolalilty
What is osmotic pressure
The prevention of water moving by applying pressure
The pressure applied to stop the flow of water
How does the plasma membrane Ca2+ ATPase work
An example of a primary active transporter
Transport calcium out fo the cell using ATP
What is the sodium potassium ATPase pump
3 sodium out for 2 potassium in
Generate ion gradients that allow secondary active transport And action potentials
Only a small contribution to resting membrane potential
What is responsible for membrane potential
Potassium diffusion through channels `
What is the sodium glucose co transporter
Entry of sodium ions provides the energy for he entry of glucose against its concentration gradient
Uses ATP
Symport
How does serca control resting Ca2+
Serca accumulates Ca2+ into the SR/ER
It has a high affinity but a low capacity
How is calcium concentration controlled by active transport
Secondary active transport
Sodium/calcium exchange anti port
Low affinity high capacity
Removes most calcium
How is cell volume regulated
Transport of osmotically active ions
Cell swelling- extrude ions ‘
Cell shrinking- influx ions
Water will flow the ions
Name the 2 primary active transporters that help maintain or decrease intracellular ca2+ levels
PMCA SERCA
In ischaemia how does the NCX contribute to more damage
During ischemia, the lack of oxygen prevents the production of ATP. Without ATP, the Na-K-ATPase is inhibited and leads to intracellular concentration of Na rising. This leads
to the reversal of the NCX causing it to exchange intracellular Na for extracellular Ca.
This reversal leads to accumulation of intracellular Ca, which is toxic to the cell, therefore causing cell death or necrosis.
