Cell Physiology of Ions 1 Ions, Fluids, Electricity

Question 1

What are the Fluid Compartments of the body? (4)

Answer 1

1. Plasma - Na+ based
2. Interstitial fluid - Na+, based but lacks blood proteins (anions)
3. Intracellular fluid - K+ based, contains lots of proteins (anions)
4. Transcellular Fluid - in the lumen of tubes and organs e.g urine, chyme

Question 2

Name some important ions in the body, in terms of anions and cations?

Answer 2

Cations include Na+, K+, Ca2+, H+, Mg2+

Anions include OH-, Cl-, HCO3-, [SO4]2-, [PO4]3-, charged proteins

Question 3

What are the different ways ions can exist in the body in terms of binding, name from weakest to strongest? (6)

Answer 3

1. Free in solution
2. Buffered (non-specific)
3. Chelated (in coordinate bonds)
4. Tightly bound
5. Sequestered - behind organelles
6. Teeth, Bones

Question 4

What are the different ways ions can pass through a membrane? (5)

Answer 4

1. Channels
2. Pump
3. Leak
4. Co-transport
5. Exchangers

Question 5

What are some functions of ions? (7)

Answer 5

1. Start cellular processes
2. Act as second messenger
3. Transmit information across the cell
4. Activate Enzymes
5. Control Transmembrane voltage
6. Create ATP
7. Move water

Question 6

What are examples of things that can happen due to ion imbalance? (5)

Answer 6

1. Cardiac Arrhythmias
2. Nervous dysfunctions e.g Tics
3. Bone deformities
4. Oedema
5. Seizures

Question 7

What can cause ion imbalances, name at least 5? (8)

Answer 7

1. Haemmorhage, Trauma
2. Extensive Diarrheoa and Vomiting
3. Hormonal imbalances
4. Diabetes
5. Vitamin D imbalances
6. Poisons
7. Kidney Dysfunction
8. Diuretics

Question 8

What is voltage? (2)

Answer 8

1. The potential energy difference between 2 points in an electrical field.
2. This means it is the driving force for movement of charged particles.

Question 9

What are the formulas for voltage? (2)

Answer 9

V = I (current) x (R) Resistance

Conductance (g) is the reciprocal of resistance. Therefore [I = g x V]

Question 10

What is the main rules of ion balance? (3)

Answer 10

1. Any ion that leaves the cell must be replaced by another ion of same type coming into the cell.
2. Energy is used to re-establish ionic gradients across membranes e.g Na+/K+ Pump
3. Concentration of positive and negative ions must “nearly” balance.

Question 11

What role does Carbonic Anhydrase play in maintaining blood pH? (3)

Answer 11

It is an enzyme that catalyses the reversible reaction CO2 + H2O -> H2CO3 -> H+ + HCO3-. Creating acid and base.

This is important as:

1. H+ is charged and cannot readily cross cell membrane so indirectly helps process of H+ crossing cell membrane and epithelia.
2. Helps indirectly transport Co2 around the body as it is poorly soluble in blood. H+ and HCO3- are.

Question 12

How is Carbonic Anhydrase used to maintain Homeostasis in:

1. Red Blood cells
2. Lungs
3. Gastric Parietal Cells
4. Pancreas (4)

Answer 12

1. Red Blood Cells = “Chloride shift” for removing H+ ions from muscle.
2. Lungs = Removing CO2 from the blood
3. Gastric Parietal cells = Secreting Acid into Stomach
4. Pancreas = Secreting bicarbonate

Question 13

Describe how Carbonic anhydrase catalyses the formation of HCL into stomach in the gastric parietal cell? (6)

Answer 13

1. CO2 and H2O enter cell through basolateral membrane.
2. CA catalyses reaction to H+ and HCO3-.
3. H+ is exchanged for K+, entering stomach lumen through the apical membrane.
4. HCO3- is exchanged for Cl- through the basolateral membrane
5. Cl- is transported into lumen via apical membrane.
6. H+ and CL- form HCL in lumen.