Cellular Physiology

Question 1

[Na⁺]

Answer 1

ECF: 135 - 147 mM

ICF: 10 - 15 mM

Question 2

[K⁺]

Answer 2

ECF: 3.5 - 5.0 mM

ICF: 120 - 150 mM

• Set point: genetically encoded
• Mechanism to monitor the deviations from the set point: glomerulosa cells of the adrenal gland
• Elevation of extracellular potassium ion concentration: aldosteron production
• Aldosteron acts on particular kidney cells, potassium
  ion excretion from the body is going to increase
• Decrease of extracellular potassium ion concentration: negative feedback control

Question 3

[Ca²⁺]

Answer 3

ECF: 2.1 - 2.8 mM (total, blood plasma) 1.1 - 1.4 mM (free)

ICF: 100 nM (free)

Question 4

[Cl^-]

Answer 4

ECF: 95 - 105 mM

ICF: 20 - 30 mM

Question 5

[HCO₃^-]

Answer 5

ECF: 22 - 28 mM

ICF: 12 - 16 mM

Question 6

Osmolality

Answer 6

ECF: 290 mOsm

ICF: 290 mOsm

Question 7

pH

Answer 7

ECF: 7.38 - 7.42 (7.4 in average) (more basic than ICF)

ICF: 7.2 (more acidic than ECF)

Question 8

Physiological control mechanisms

Answer 8

• Negative feed-back: maitenance of homeostatis
• Positive feed-back: increase of activation (ovulation, gating of ion channel)
• Servo-control regulation: set point has been changed (fever, exercise)
• Feed-forward control: effector is also disturbed (thermo-, osmoregulation)

Question 9

Plasma membrane lipids

Answer 9

Question 10

Total body water (TBW) (for an individual weighing 70 kg)

Answer 10

0.6 body weight: 42L

Question 11

Extracellular fluid (ECF) (for an individual weighing 70 kg)

Answer 11

0.2 body weight: 14L

Question 12

Intracellular fluid (ICF) (for an individual weighing 70 kg)

Answer 12

0.4 body weight: 28L

Question 13

Interstitial fluid (for an individual weighing 70 kg)

Answer 13

3/4 of ECF: 10.5L

Question 14

Plasma (for an individual weighing 70 kg)

Answer 14

1/4 of ECF: 3.5L

Question 15

Transcellular fluid

Answer 15

• Cerebrospinal fluid
• Ocular fluid
• Synovia (joint fluid)
• Fluids in the pleural cavity
• Fluids in the peritoneal cavity

Question 16

Measurements of the volume of various fluid compartments

Answer 16

Dilution method: V=m/c

• Total fluid compartment: deuterium
• Extracellular fluid: inulin
• Blood plasma: protein, protein-bound dye (Evans-blue)

Question 17

Mechanism of diffusion

Answer 17

Random movement of solute due to the Brownian motion.

Question 18

Fick’s first law of diffusion

Answer 18

J= DAΔc/Δx

• J: net rate of diffusion (in moles per unit time)
• D: diffusion coefficient (rate depends on the hydrophobicity and the size of the solute)
• A: area, across which the diffusion is occuring
• Δx: distance, along whics the diffusion is occuring (thickness of the membrane)
• Δc: concentration difference (driving force)

Question 19

van’t Hoff’s law of osmotic pressure

Answer 19

π= RTnc

• π: osmotic pressure
• n: number of dissociable particles per molecule
• c: total solute concentration
• R: gas constant
• T: temperature in degrees Kelvin