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Physiology I > W1 - Cellular physiology (1.1) > Flashcards

W1 - Cellular physiology (1.1) Flashcards

1
Q

What percentage of the total body weight is water in an adult?

Classify + values.

A

60% ∽42l

  • 2/3, hence 40% intracellular fluid (ICF) ∽ 25l
  • 1/3, hence 20% extracellular fluid (ECF) ∽ 17l
    • 3/4 of ECF, hence 15% interstitial fluid ∽13l
    • 1/4 of ECF, hence 5% plasma ∽ 3l
    • transcellular fluid ∽ 1l

​REMEMBER: 60-40-20 rule for water-ECF-ICF

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2
Q

What is the total blood volume of the body?

Constituents.

A

∽ 5l (water)

  • ∽ 3l plasma (ECF)
  • ∽ 2l in cells (ICF)

→ seperated by capillary blood cell membrane

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3
Q

What is measured for a complete blood count?

Values.

A
  • RBC count = 4.1 - 6.1 *10^6 cells/μl
  • WBC count = 4,000 - 11,000 cells/μl
  • thrombocyte count = 150,000 - 400,000 cells/μl
  • Hb:
    • men: 160 - 170g/l
    • women: 135 - 145g/l
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4
Q

Which fraction is described by the hematocrit?

Values.

A

volume percentage of red blood cells in blood

  • men: 40 - 52% (∽ 45%)
  • women: 37 - 48% (∽ 40%)
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5
Q

What are the percentages of different WBC types?

A
  • lymphocytes = 25 - 30%
  • monocytes = 4 - 8%
  • neutrophil granulocytes = 40 - 70%
  • eosinophil granulocytes = 2 - 4%
  • basophil granulocytes = 0 - 1%
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6
Q

Which fluid compartments do also belong the group of interstitial fluid?

A
  • bone
  • dense connective tissue
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7
Q

What is transcellular fluid?

Examples.

A

body water found in epithelial lined compartments

  • cerebrospinal fluid (liquor)
  • ocular fluid
  • synovia
  • fluids in pleural cavity
  • fluids in peritoneal cavity
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8
Q

Give values for [Na+] in ECF and ICF.

A
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9
Q

Give values for [K+] in ECF and ICF.

A
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10
Q

Give values for [Ca2+] in ECF and ICF.

A
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11
Q

Give values for [Cl-] in ECF and ICF.

A
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12
Q

Give values for [HCO3-] in ECF and ICF.

A
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13
Q

Give values for osmolality of ECF and ICF.

A
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14
Q

Give values for pH of ECF and ICF.

A
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15
Q

How is the volume of fluid compartments measured?

Examples.

A

dilution method

  1. known amount of tracer is added to a compartment
  2. tracer concentration is measured after sufficient time for uniform distribution throughout the compartment
  3. compartment volume calculated
    * *V = amount of tracer/conc. of tracer**
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16
Q

List examples for tracers.

Function?

A

​examples for tracers:

  • total fluid: deuterium
  • ECF: inulin
  • blood plasma: protein, protein bound dye (Evans blue)
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17
Q

Differentiate btw lipid classes that can be found in the plasma membrane.

Where are the located, inner or outer leaflet?

What is their function?

A
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18
Q

Lipid-anchored membrane proteins are either … ?

A
  • GPI-bound proteins, or
  • bound to palmitoylated fatty acids
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19
Q

What is the difference btw channels and carriers?

Also refer to energetically transport mode, speed and kinetical properties.

A
  • channel = gated, undergoes conf. change to open & close
  • carrier = enzyme, undergoes conf. change to transport molecule from inside to outside, or vice versa
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20
Q

What is passive, primary, and secondary active transport?

A
  • passive: along conc. gradient
  • prim. active: transport against conc. gradient, directly coupled to hydrolysis of ATP
  • sec. active: transport against electrochem. gradient, using energy of electrochem. gradient of other mol.
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21
Q

What does Fick’s first law state?

A

rate at which a molecule diffuses from point A to B

J = DA/Δx * Δc

  • J = flux or rate of diffusion in [mol/sec]
  • D = diffusion coefficient
  • A = area across which diffusion is occurring
  • Δc = concentration difference
  • Δx = distance along which diffusion is occurring
22
Q

The diffusion rate depends on… ?

A
  • Δx = thickness of membrane
  • Δc = conc. difference btw the 2 sides of the membrane, driving force
  • D = diffusion coefficient (incorp. hydrophobicity + size of solute)
23
Q

Which molecules are diffusible, partially diffusible, or non-diffusible through the plasma membrane?

A
  • diffusible: gases (O2, CO, CO2, NO), hydrophobic molecules, hormones
  • diffusible, using channels: water, ions, glucose
  • non-diffusible: peptides, proteins, disaccharides
24
Q

Give examples for different transporters used for facilitated transport.

A
  • uniporter, e.g. GLUT-transporters
  • symporters, e.g. Na/K/Cl cotransporter NKCC2 for concentrating urine in kidney (cf. picture for more)
  • antiporters, e.g. Na-H exchanger NHE-1 to regulate pH (cf. picture for more)
25
Q

Describe the structure of GLUT-transporters.

A
  • 12 amphiphilic transmembrane proteins in plasma membrane
  • hydrophobic ends binding outwards in plasma membrane, hydrophilic pocket formed inside
  • N-, C-terminals in cytosol

​→ conf. change transports glucose molecule

26
Q

What is the difference btw GLUT 1, 2, and 4?

A
  • GLUT 1: most common type, esp. in CNS and erythrocytes, high affinity for glucose, almost always saturated
  • GLUT 2: e.g. in hepatocytes, small intestine, low affinity for glucose, hence gluc uptake dependent on blood sugar level → inhibits glycogen breakdown in liver
  • GLUT 4: in adipocytes and skeletal muscle, insulin sensitive, high affinity, glucose is taken up if insuline level is high → lowers blood sugar
27
Q

What is the inhibitor of Na+/K+ - ATPase?

A

quabain

28
Q

What is the importance of CSTR?

Explain.

A

= cystic fibrosis transmembrane regulator
Cl- channel not coded in case of cystic fibrosis

→ defective epithelial transport, no mucus transport out of the lung

⇒ chronic lung infections, pancreatic insufficiency, infertility in males ⇒ death due resp. failure

29
Q

What is driving force of water?

A

osmosis

→ water flows to where osmotic concentration is higher (↑ osmotic pressure)

30
Q

What does van’t Hoff’s law state?

A

osmotic pressure is solely dependent on the number of molecules in the solution
→ it does not depend on size, mass, or chemical nature

π = nCRT

  • π = osmotic pressure in [atm]
  • n = no. of dissociable particles per molecule
  • C = total solute conc.
  • R = gas constant
  • T = temperature in degrees Kelvin
31
Q

What is the difference btw osmolarity and osmolality?

A
  • osmolarity = conc. * no. of dissociable particles
    in [mOsm/l]
  • osmolality in [mOsm/kg]

​⇒ osmolality is independent of temperature, hence the preferred term to describe biological systems

32
Q

What is tonicity?

Classify.

A

effect of the solution on the volume of a cell
⇒ related to osmolality, but also considers ability of a mol. to cross the cell membrane

  • hypotonic = causes a cell to swell
  • isotonic = does not affect the volume of a cell
  • hypertonic = causes a cell to shrink
33
Q

What is described by the reflection coefficient?

Explain 2 related important terms.

A

reflection coefficient σ is a measure of the rel. ability of a molecule to cross the cell membrane

π = σ (nCRT)

  • effective osmole: substance that is not able to cross the membrane, hence exert osmotic pressure
  • ineffective osmole: substance that is able to cross the membrane, hence does not exert osmotic pressure
34
Q

What is oncotic pressure?

A

osmotic pressure generated by large molecules (esp. proteins), bc pressure generated not conform w/ van’t Hoff’s law

35
Q

Which organs are layered by epithelial cells?

A
  • skin
  • GI tract
  • exocrine glands
  • kidney
  • lungs
  • testes
36
Q

What is the function of microvilli, sterocilia, and kinocilia?

A
  • microvilli: incr. surface area
  • stereocilia: incr. surface area
  • stereocilia: transport mucus

​+ diff. structural arrangement (cf. book)

37
Q

What are different directions of cellular transport?

A
  • excretion/secretion: interstitial → luminal
  • re-/absorption: luminal → interstitial:
  • vectorial/transcellular transport: through an epithelial cell
  • paracellular transport: through space btw the cells (epithelium)
38
Q

What is transcellular transport?

List important features.

A

​transport across an epithelial cell

  • 2 step process - uptake, transport out: 1 step usually passive (gradient), 1 active (pump)
  • location of transporter (pumps, passive carriers, ion/water channels) on membrane domain depends direction
  • needs energy (pump)
39
Q

In which membrane domain is the Na+, K+ - ATPase located?

Any exceptions?

A

ALWAYS in basolateral membrane,

except: choroid plexus

40
Q

List important features of paracellular transport.

Examples

A

transport through space btw epithelial cells that involves tight junctions

  • passive
  • can be selective
  • permeability of tight junctions often determines rate of transepithelial transport (high perm. → high rate), determined by claudins​, i.e.
    • ​prox. tubule of nephron, jejunum = leaky, high perm.
    • collecting ducts, terminal portion of colon = tight, low perm.
41
Q

What is ENaC?

What is it used for, which other channels are involved?

A

highly selective type of epithelial Na channel on apical surface

⇒ together w/ Na+/K+/ATPase and K+ channels (both on basolateral membrane) resp. for transcellular Na transport

42
Q

Where does transepithelial Na transport happen?

A
  • on frog skin
  • distal tubule
  • sweat glands
43
Q

Describe the mechanism of transepithelial Na transport.

A
  1. transcellular transport:
    • Na+ diffuses through ENaC on apical surface into cell
    • 3 Na+ pumped out, 2K+ pumped in, K+ diffuses out of cell involving Na+/K+/ATPase and K+ channels (both on basolat. surface)
  2. paracellular transport:
    • Cl- diffuses along conc. gradient into lume n
    • H20 diffuses due to osm. pressure into lumen

⇒ water reabsorption in NaCl solution

44
Q

Which substances regulate ENaC, hence reabsorption of water?

A
  • modulated by aldosterone
  • inhibited by amilorid (= diuretic agent)
45
Q

Which components are involved in glucose reabsorption in the small intestine and proximal tubules?

A
  • Na+/K+/ATPase
  • channels (aquaporins, K+)
  • cotransporter (SGLT 1/2)
  • uniporter (GLUT-2)
46
Q

What is the difference btw SGLT 1 and 2?

A

​both present on luminal side of cell

  • SGLT 1: in straight portion of prox. tubule, minor role
  • SGLT 2: in prox. convoluted tubule, major role
47
Q

Explain the mechanism of glucose reabsorption.

A

transcellular transport

  1. Na+ pumped out of, K+ pumped into cell, K+ diffuses out through channels (on basol. surf.)
  2. SGLT cotransports Na+, gluc along Na+ conc. gradient into cell on apical surf.
  3. GLUT-2 on basol. surface transports glucose into compartment
  4. H2O gets reabsorbed
48
Q

Which components are involved in NaCl secretion in salivary glands and small intestine?

A
  • Na+/K+/ATPase
  • cotransporter (Na+/K+/Cl-)
  • channels (K+, aquaporins, Cl-, e.g. CFTR)
  • paracellular Na+, H20 transport
49
Q

Explain the mechanism of NaCl secretion.

A
  1. Na+ pumped out of, K+ pumped into cell by the action of Na+/K+/ATPase, 2 Cl- cotransported w/ K+, Na+ into cell on basolat. surf.
  2. K+ diffuses out of cell on basolat. surf
  3. Cl- diffuses on apical surface out of cell through Cl- channels
  4. Na+, H20 diffuses due to osm. pressure and electrochem. gradient paracellularly into lumen
50
Q

Where can H+ secretion be observed?

A

on parietal cells in stomach → secretion of HCl8

51
Q

Explain the mechanism of HCl secretion in the stomach.

A
  1. metabolism:
    CO2 + H2O → H2CO3 → H+ + HCO3-
  2. H+ actively pumped out K+ pumped into, K+ diffuses out again (on apic. surf.)
  3. HCO3- transported out, Cl- transported into cell on basolat. surf.
  4. Cl- diffuses out of cell on apic. surf.

Physiology I (10 decks)

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