L4 & L5 Cell physiology of ions Flashcards
What is a solvent? [3]
Fluid present
Biological systems it is water
Organic fluids in lab
What is a solute? [3]
particles dissolved in solvent
Can be atoms & molecules
DNA, sugars, proteins and H+ ions
What is an electrolyte?
ionized components of living fluid
important ions to remember
Na+, K+, Ca2+, H+, Mg2+, OH-, Cl-, HCO3_, SO4-, PO4-& charged proteins
What is PO4- used for?
important for reactions involving ATP (enzyme) and structurally in bone
What is SO4- used for?
is important structurally in glycosaminoglycan (connective tissue )
Fluid compartments Plasma Interstitial Intracellular Transcellular
Plasma: Na+ based
Interstitial: ~ plasma and lacks blood proteins
Intracellular: K+ based and lots of protein
Transcellular: In the lumen of tubes and organs (CSF, urine in bladder, chyme in GIT)
Methods of transport
Channels Pumps Transporters Exchangers Leak
What are the following?
Channels Pumps Transporters Exchangers Leak
Channels: membrane proteins that open/close and let specific ions flow down a concentration gradient (passive)
Pumps: membrane proteins that use ATP to pump ions across membrane (against concentration gradient)
Transporters = membranes proteins that couple the transport of two different molecules so that both go across membrane together (passive)
Exchangers: membrane proteins that couple the transport of two different molecules (opposite directions) Passive
Leak: Movement of ions across a membrane (passive) no protein to facilitate
Ions - where??
Free Tightly bound Sequestered Chelated Buffered - can go in/out solution Teeth and bones
Role of ions [2]
Start cellular process - act as 2nd messenger
Involved in muscle contraction - fertilisation and exocytosis
Create energy (ATP), activate enzymes (protein kinase C), move water (kidney) and control transmembrane voltage
Wrong ion concentration can lead to? [4]
Cardiac arrhythmias, bone deformities, oedema and seizures
Causes of ionic imbalance [8]
Trauma/haemorrhage Diabetes Kidney dysfunction Hormonal imbalance Extensive D and V Dehydration Vit D imbalance poisons
Voltage [4]
Difference in potential energy between 2 points in an electric field
V=IR G = I/V
G = conductance (ability for current to flow at given voltage)
What are the ionic differences in a cell?
K+ inside, na+ outside
cell membrane is not permeable to be charged ions, but it is permeable to water and uncharged molecules
What is a chemical force?
= Diffusional force
based on concentration difference across membrane
10 x Na+ outside, 30x potassium in intracellular/extracellular
What is an electrical force?
Based on Vm (membrane potential -> varies over time)
Based on a few positive charges
Same for all ions
What is a net force?
chemical + electrical force
What happens at equilibrium, in terms of charges?
-1 x electrical force
net force = 0
What is hypocalcaemia?
Low calcium
Can lead to ECG abnormalities and arrhythmyia
Level of ions maintained in
Cytosol of cell
Excitable cells can…
Propagate action potential (amplified voltage response)
Neurons and muscle cells
Non-excitable examples
Skin and liver (esp epithelial cells)
Plasma composition
Highest in Na+ concentration (to balance protein anions)
Is slightly more negative in electric potential than the Extracellular Fluid (ECF)
Intracellular fluid composition
Highest in total cations
Highest in proteins
Highest electrolyte concentration (milliEquivalents)
Most negative voltage
Free Calcium summary
Calcium ionised AND in solution -> free to activate enzymes
Found in bone of insoluble solid, bound to protein or sequestered inside cellular organelles
Cytosolic calcium amount in cytosol vs extracellular
Low in cytosol
~ 100 nanoM
Cf extracellular is +1.2milliM
Change in voltage can lead to…
Second Messenger: Calcium, kinases, phospholipases
Contaction in muscles
3 rules
The concentration of positive and negative ions must “nearly” balance
Any ion that leaves the cell must be replaced soon by another ion of that type coming into the cell
Energy is always being used to re-establish the ionic gradients across membranes
pH
extracellular fluid (7.40 ± 0.05)
cytosol (7.20, although this can vary based on the cell type).
Changes in blood pH are corrected by the actions of the kidneys and the lungs.
Carbonic anhydrase
Create base or acid
Indirectly contribute to H+ crossing membrane and epithelia
Indirectly transport CO2 around body (CO2 is poorly soluble in blood)
Carbonic Anhydrase in Homeostasis
Red Blood Cells: “Chloride shift” for removing H+ from muscle
Lungs: for eliminating CO2 source from blood
Gastric Parietal cells: secreting acid into stomach
Pancreas: secreting bicarbonate
What does the Sodium-potassium pump (Na / K ATPase) do?
maintains the intracellular K+ concentration. It is inhibited by ouabain and digitalis
What inhibits the H+ / K+ ATPase “Proton Pump” ?
active, uses up ATP energy
Inhibited by omeprazole (a proton pump inhibitor PPI)
