Cell Physiology of Ions 1

Question 1

Define: Solvent, Solute, Ionic Gradient

Answer 1

=
the fluid present
- In all biological systems it is water
- In the lab it can be organic fluids
eg ethanol
=
particles dissolved in solvent
- Can be atoms, molecules
- Examples: DNA, sugars, proteins, H+ ions
=
-the difference in concentration of ions between two points in space
-Typically refers to the differences across a membrane
-A voltage gradient is a difference in voltage across the membrane

Question 2

Fluid Compartments of the Body - Ion concentration

Answer 2

= Plasma
Na+ based
= Interstitial 
~ plasma
lacks blood proteins (anions)
= Transcellular
in the lumen of tubes and organs 
Cerebrospinal fluid, urine in bladder, chyme in GI tract
= Intracellular
K+ based 
lots of protein (anions)

Question 3

Diffusion and osmosis

Answer 3

process of solute/solvent (water) molecules passively moving down their concentration gradient

Question 4

Define:
Ion
Cation
Anion
Electrolytes

Answer 4

Ion = charged atom or molecule
Example: H+ is a charged hydrogen atom, and it is also technically a single proton
Things that are not ions: glucose, H2O, most proteins (eg actin)

Cation = positively charged ion
Example: Na+ is a positively charged sodium atom

Anion = negatively charged ion
Example: Cl- is a negatively charged chloride atom

Electrolytes = ionized components of living fluid (e.

Question 5

Ions where are they?

Answer 5

• Free
• Tightly bound
• Sequestered
• Teeth/bones
• Buffered
• Chelated

Question 6

Ions cross the membrane via:

Answer 6

• Channels
• Exchangers
• Leak
• Co-transporters
• Pump (Active)

Question 7

Ions different function

Answer 7

• Fertilisation
• Exocytosis
• Muscle contraction
• Second messenger
• Create energy
• Move water
• Activate enzyme
• Control Transmembrane Voltage

Question 8

Consequences of wrong concentration

Answer 8

• Cardiac arrhythmias
• Tics and other nervous dysfunctions
• Seizures
• Oedema
• Bone deformities

Question 9

Causes of ionic imbalances

Answer 9

• Trauma & Haemorrhage
• Diabetes/ Diuretics
• Kidney dysfunction
• Hormonal imbalances
• Dehydration/ Poison/ Vit D imbalance
• Extensive Diarrhoea and Vomiting

Question 10

Define Voltage and give the formula

Answer 10

It is the difference in potential energy between 2 points in an electrical field
Which is the electrical potential or driving force for charged particles (ions) to move

V= I x R
I= g x V (preferable one)

Question 11

Relative to the Vm and the RMP, when is the cell considered to be at rest.

Answer 11

Vm is equal to RMP

Question 12

describe what happens during an AP with regards to the membrane potential and the overall ion concentration gradients.

Answer 12

the Vm changes dramatically whereas the concentration gradient barely changes.

Question 13

Differences between chemical and electrical force

Answer 13

Chemical
- Also called diffusional force
- Is based upon the difference in concentration ACROSS the membrane
E.g. If there is 10X as much Na+ outside than inside, the chemical force on Na+ channels is 60 mV directed into the cell
=
Electrical
- This is based on Vm (the membrane potential, which varies over time).
-This is based on a few positive charges being UNPAIRED with negative charges ON THE SAME SIDE OF THE MEMBRANE, so there are slightly more positive charges on one side of the membrane than the other
*the type of ion isn’t relevant so long as it is the same charge.

Question 14

Equilibrium potential formula

Answer 14

Net force = chemical + electrical force