Cell Physiology of Ions 1 Flashcards
What does a concentration gradient of ions lead to?
A voltage/potential difference
What are the 3 main fluid compartments?
Intracellular, Extracellular (intercellular), transcellular
What makes up extracellular fluid?
Interstitial and blood plasma
Blood plasma
Na+ based. Non-cellular component of extracellular fluid; constantly exchanges substances with interstitial fluid through pores of capillary membranes so has similar composition. Higher protein concentration than interstitial.
Why does blood plasma have higher protein concentration than interstitial fluid?
Because the capillary pores are very permeable to many solutes except proteins.
Interstitial fluid
Similar to plasma, similar composition as only separated by very permeable capillary membrane. Lower protein content than plasma.
Transcellular fluid
Specialised extracellular fluid with its own compartments e.g. fluid in lumen of tubes/organs. Cerebrospinal fluid, urine in bladder
Intracellular fluid
K+ based. Lots of proteins (anions).
Diffusion
Tendency of molecules to move passively down their concentration gradient. Involves solute, not solvent
Osmosis
Tendency of water molecules to move passively from a region of high water potential to a region of low water potential
Give 6 forms/places in which you can find ions in the body
Free in solution, tightly bound to another molecule, sequestered, chelated, buffered, teeth and bones
Sequestered
Ions behind membrane of organelle e.g. in a vesicle or mitochondria
Chelated
Ion specifically bound to a molecule, high affinity
Buffered
Ion non-specifically bound to a molecule, low affinity so easily dissociates
Name 5 ways of ions crossing membrane
Ion channels, ion pumps, ion exchangers, co-transporters, ionic leaks
Ion channels
Passive, facilitated by intrinsic proteins, open and close for specific ions
Ion pumps
Active. Uses proteins. e.g. Na-K pump
Ionic leak
Passive. Unexplained movement of ions across CM.
Ionic exchangers
Passive. Membrane proteins that move one molecule out and one in, simultaneously.
Co-transporters
Membrane proteins that move two molecules together in same direction. Passive so at least one of the molecules must be going down concentration gradient.
Name 6 functions of ions
Start cellular processes, act as secondary messengers, create ATP, move water (in kidney), activate enzymes, control transmembrane voltage
What is an example of a first messenger?
A hormone or neurotransmitter. Only reaches the outside of cells
What is a secondary messenger? Give examples
A molecular mechanism for transmitting chemical signals from outside cell membrane to throughout the inside of the cell. Kinase reactions, G proteins, adenylate cyclase (which forms cyclic AMP inside cell)
Examples of when secondary messengers are used.
Muscle contraction, exocytosis
How are ions involved in moving water in kidneys?
Water usually follows the movement of chloride ions; so water reabsorbed into blood during re-absorption
How are ions involved in activating enzymes?
Protein Kinase C is activated when Ca+ ions are nearby. Protein Kinase C phosphorylates things.
Give 5 issues that can occur if you have abnormal concentrations of ions?
Cardiac Arrhythmias, Tics and other nervous dysfunctions, seizures, bone deformities, oedema
Explain how cardiac arrhythmias arise due to ion concentration abnormalities
Heart muscles are electrically disorganised, leading to failure of heart to beat regularly.
Explain how ion concentration issues lead to seizures
The brain is overexcitable so neurons fire for no good psychological procedure
Give examples of which ion deficiencies lead to which bone deformities
Calcium deficiency leads to rickets and potassium deficiency leads to rickets too.
Explain how oedema arises.
Due to abnormally high concentration of ions in extracellular fluid, fluid accumulates
Causes of ionic imbalances in patients
Trauma/haemorrhage, diabetes (over loss of H2O so loss of ions), kidney disfunction (loss of H2O), hormonal imbalances, extensive Diarrhoea and vomiting, poisons
Which ions form the majority of cations inside and outside cells?
K+ forms majority of cations inside cell. Na+ forms majority of cations outside cells
How do electrical currents arise across membranes?
The movement of ions across membranes
During the Action potential, which potential changes?
The membrane potential, Vm
What is Vm based upon?
The imbalance between positive and negative charges across a membrane
Do all ions feel the same electrical field and chemical drive?
Same electrical field but different chemical drive.
Relatively how many ions need to move to change the membrane potential drastically? How are the concentrations of ions affected
A very small number of ions, so concentrations are virtually unchanged.
If ions move across a membrane (into a cell) without equal number of oppositely charged ions, what happens in terms of forces?
Strong electric field forms across membrane, pushing ions across membrane to regain equilibrium of charge each side of membrane. Chemical force virtually unchanged as concentrations virtually unchanged.
