Cell Physiology of Ions 1

Question 1

What does a concentration gradient of ions lead to?

Answer 1

A voltage/potential difference

Question 2

What are the 3 main fluid compartments?

Answer 2

Intracellular, Extracellular (intercellular), transcellular

Question 3

What makes up extracellular fluid?

Answer 3

Interstitial and blood plasma

Question 4

Blood plasma

Answer 4

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.

Question 5

Why does blood plasma have higher protein concentration than interstitial fluid?

Answer 5

Because the capillary pores are very permeable to many solutes except proteins.

Question 6

Interstitial fluid

Answer 6

Similar to plasma, similar composition as only separated by very permeable capillary membrane. Lower protein content than plasma.

Question 7

Transcellular fluid

Answer 7

Specialised extracellular fluid with its own compartments e.g. fluid in lumen of tubes/organs. Cerebrospinal fluid, urine in bladder

Question 8

Intracellular fluid

Answer 8

K+ based. Lots of proteins (anions).

Question 9

Diffusion

Answer 9

Tendency of molecules to move passively down their concentration gradient. Involves solute, not solvent

Question 10

Osmosis

Answer 10

Tendency of water molecules to move passively from a region of high water potential to a region of low water potential

Question 11

Give 6 forms/places in which you can find ions in the body

Answer 11

Free in solution, tightly bound to another molecule, sequestered, chelated, buffered, teeth and bones

Question 12

Sequestered

Answer 12

Ions behind membrane of organelle e.g. in a vesicle or mitochondria

Question 13

Chelated

Answer 13

Ion specifically bound to a molecule, high affinity

Question 14

Buffered

Answer 14

Ion non-specifically bound to a molecule, low affinity so easily dissociates

Question 15

Name 5 ways of ions crossing membrane

Answer 15

Ion channels, ion pumps, ion exchangers, co-transporters, ionic leaks

Question 16

Ion channels

Answer 16

Passive, facilitated by intrinsic proteins, open and close for specific ions

Question 17

Ion pumps

Answer 17

Active. Uses proteins. e.g. Na-K pump

Question 18

Ionic leak

Answer 18

Passive. Unexplained movement of ions across CM.

Question 19

Ionic exchangers

Answer 19

Passive. Membrane proteins that move one molecule out and one in, simultaneously.

Question 20

Co-transporters

Answer 20

Membrane proteins that move two molecules together in same direction. Passive so at least one of the molecules must be going down concentration gradient.

Question 21

Name 6 functions of ions

Answer 21

Start cellular processes, act as secondary messengers, create ATP, move water (in kidney), activate enzymes, control transmembrane voltage

Question 22

What is an example of a first messenger?

Answer 22

A hormone or neurotransmitter. Only reaches the outside of cells

Question 23

What is a secondary messenger? Give examples

Answer 23

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)

Question 24

Examples of when secondary messengers are used.

Answer 24

Muscle contraction, exocytosis

Question 25

How are ions involved in moving water in kidneys?

Answer 25

Water usually follows the movement of chloride ions; so water reabsorbed into blood during re-absorption

Question 26

How are ions involved in activating enzymes?

Answer 26

Protein Kinase C is activated when Ca+ ions are nearby. Protein Kinase C phosphorylates things.

Question 27

Give 5 issues that can occur if you have abnormal concentrations of ions?

Answer 27

Cardiac Arrhythmias, Tics and other nervous dysfunctions, seizures, bone deformities, oedema

Question 28

Explain how cardiac arrhythmias arise due to ion concentration abnormalities

Answer 28

Heart muscles are electrically disorganised, leading to failure of heart to beat regularly.

Question 29

Explain how ion concentration issues lead to seizures

Answer 29

The brain is overexcitable so neurons fire for no good psychological procedure

Question 30

Give examples of which ion deficiencies lead to which bone deformities

Answer 30

Calcium deficiency leads to rickets and potassium deficiency leads to rickets too.

Question 31

Explain how oedema arises.

Answer 31

Due to abnormally high concentration of ions in extracellular fluid, fluid accumulates

Question 32

Causes of ionic imbalances in patients

Answer 32

Trauma/haemorrhage, diabetes (over loss of H2O so loss of ions), kidney disfunction (loss of H2O), hormonal imbalances, extensive Diarrhoea and vomiting, poisons

Question 33

Which ions form the majority of cations inside and outside cells?

Answer 33

K+ forms majority of cations inside cell. Na+ forms majority of cations outside cells

Question 34

How do electrical currents arise across membranes?

Answer 34

The movement of ions across membranes

Question 35

During the Action potential, which potential changes?

Answer 35

The membrane potential, Vm

Question 36

What is Vm based upon?

Answer 36

The imbalance between positive and negative charges across a membrane

Question 37

Do all ions feel the same electrical field and chemical drive?

Answer 37

Same electrical field but different chemical drive.

Question 38

Relatively how many ions need to move to change the membrane potential drastically? How are the concentrations of ions affected

Answer 38

A very small number of ions, so concentrations are virtually unchanged.

Question 39

If ions move across a membrane (into a cell) without equal number of oppositely charged ions, what happens in terms of forces?

Answer 39

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.