Lecture 4: Cell Physiology of Ions 1

Question 1

what are the fluid components of the body?

Answer 1

• plasma (sodium based)
• intracellular (potassium based with lots of anion proteins)
• interstitial (sodium based but lacks anion blood proteins)
• transcellular (in lumen of tubes and organs)

Question 2

examples of transcellular fluid

Answer 2

• cerebrospinal fluid
• urine in bladder
• chyme in gastrointestinal tract

Question 3

what are electrolytes

Answer 3

ionised components of living fluid

Question 4

where are ions found / stored

Answer 4

• free: in solution
• buffered: non-specifically bound to another molecule eg protein
• chelated: high affinity specific binding to a protein or other molecule
• tightly bound to a surface
• sequestered in a vesicle or compartment, eg Ca2+ in mitochondria
• Ca2+ in teeth and bones

Question 5

passive ways of transporting ions across a membrane

Answer 5

• channels
• co-transporters
• exchangers
• leaks

Question 6

active ways of transporting ions across a membrane

Answer 6

pumps

Question 7

functions of ions

Answer 7

• act as secondary messengers
• start cellular processes
• generate energy as ATP
• osmosis through kidney
• activate enzymes eg protein kinase C activated by Ca2+
• control transmembrane voltage

Question 8

incorrect concentrations of ions leads to:

Answer 8

• cardiac arrhythmia
• tics
• seizures
• long term irregularities leads to bone deformities
• oedema

Question 9

causes of ion imbalances

Answer 9

• trauma and haemorrhages
• diabetes type 1 and 2
• kidney dysfunction
• hormonal imbalances
• dehydration over the course of days
• long term vitamin D imbalance
• some poisons
• extensive diarrhea and vomiting

Question 10

what does g represent?

Answer 10

conductance, so the reciprocal of resistance

Question 11

what equation links voltage, g and current

Answer 11

I = gV

Question 12

general ion concentrations inside vs outside the cell

Answer 12

• K+ forms majority of cations inside the cell

- Na+ forms majority of cations outside the cell

Question 13

what is Vm and RMP

Answer 13

membrane potential and resting membrane potential

Question 14

the two forces on an ion and how they act

Answer 14

• chemical force, based on differences in concentrations of the ions across the membrane and depends on the particular ion moving in or out
• electrical force, based on Vm and doesn’t matter which ions are moving in / out