L4 & L5 Cell physiology of ions

Question 1

What is a solvent? [3]

Answer 1

Fluid present
Biological systems it is water
Organic fluids in lab

Question 2

What is a solute? [3]

Answer 2

particles dissolved in solvent

Can be atoms & molecules
DNA, sugars, proteins and H+ ions

Question 3

What is an electrolyte?

Answer 3

ionized components of living fluid

Question 4

important ions to remember

Answer 4

Na+, K+, Ca2+, H+, Mg2+, OH-, Cl-, HCO3_, SO4-, PO4-& charged proteins

Question 5

What is PO4- used for?

Answer 5

important for reactions involving ATP (enzyme) and structurally in bone

Question 6

What is SO4- used for?

Answer 6

is important structurally in glycosaminoglycan (connective tissue )

Question 7

Fluid compartments
Plasma 
Interstitial 
Intracellular 
Transcellular

Answer 7

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)

Question 8

Methods of transport

Answer 8

Channels 
Pumps 
Transporters 
Exchangers
Leak

Question 9

What are the following?

Channels 
Pumps 
Transporters 
Exchangers
Leak

Answer 9

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

Question 10

Ions - where??

Answer 10

Free
Tightly bound 
Sequestered 
Chelated 
Buffered - can go in/out solution 
Teeth and bones

Question 11

Role of ions [2]

Answer 11

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

Question 12

Wrong ion concentration can lead to? [4]

Answer 12

Cardiac arrhythmias, bone deformities, oedema and seizures

Question 13

Causes of ionic imbalance [8]

Answer 13

Trauma/haemorrhage 
Diabetes
Kidney dysfunction 
Hormonal imbalance 
Extensive D and V 
Dehydration 
Vit D imbalance 
poisons

Question 14

Voltage [4]

Answer 14

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)

Question 15

What are the ionic differences in a cell?

Answer 15

K+ inside, na+ outside

cell membrane is not permeable to be charged ions, but it is permeable to water and uncharged molecules

Question 16

What is a chemical force?

Answer 16

= Diffusional force
based on concentration difference across membrane
10 x Na+ outside, 30x potassium in intracellular/extracellular

Question 17

What is an electrical force?

Answer 17

Based on Vm (membrane potential -> varies over time)
Based on a few positive charges
Same for all ions

Question 18

What is a net force?

Answer 18

chemical + electrical force

Question 19

What happens at equilibrium, in terms of charges?

Answer 19

-1 x electrical force

net force = 0

Question 20

What is hypocalcaemia?

Answer 20

Low calcium

Can lead to ECG abnormalities and arrhythmyia

Question 21

Level of ions maintained in

Answer 21

Cytosol of cell

Question 22

Excitable cells can…

Answer 22

Propagate action potential (amplified voltage response)

Neurons and muscle cells

Question 23

Non-excitable examples

Answer 23

Skin and liver (esp epithelial cells)

Question 24

Plasma composition

Answer 24

Highest in Na+ concentration (to balance protein anions)

Is slightly more negative in electric potential than the Extracellular Fluid (ECF)

Question 25

Intracellular fluid composition

Answer 25

Highest in total cations
Highest in proteins
Highest electrolyte concentration (milliEquivalents)
Most negative voltage

Question 26

Free Calcium summary

Answer 26

Calcium ionised AND in solution -> free to activate enzymes

Found in bone of insoluble solid, bound to protein or sequestered inside cellular organelles

Question 27

Cytosolic calcium amount in cytosol vs extracellular

Answer 27

Low in cytosol
~ 100 nanoM

Cf extracellular is +1.2milliM

Question 28

Change in voltage can lead to…

Answer 28

Second Messenger: Calcium, kinases, phospholipases

Contaction in muscles

Question 29

3 rules

Answer 29

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

Question 30

pH

Answer 30

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.

Question 31

Carbonic anhydrase

Answer 31

Create base or acid
Indirectly contribute to H+ crossing membrane and epithelia
Indirectly transport CO2 around body (CO2 is poorly soluble in blood)

Question 32

Carbonic Anhydrase in Homeostasis

Answer 32

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

Question 33

What does the Sodium-potassium pump (Na / K ATPase) do?

Answer 33

maintains the intracellular K+ concentration. It is inhibited by ouabain and digitalis

Question 34

What inhibits the H+ / K+ ATPase “Proton Pump” ?

active, uses up ATP energy

Answer 34

Inhibited by omeprazole (a proton pump inhibitor PPI)