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CBE > Week 5.2 > Flashcards

Week 5.2 Flashcards

1
Q

Potassium homeostasis (2 main regulations)

A
  1. Intake of K+
  2. Renal secretion & urine excretion of K+
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2
Q

What mainly controls K+ homeostasis

A

Aldosterone will respond and change K+ concentration

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3
Q

What are the effects of abnormal potassium levels

A

Plasma potassium normally controls neuron excitability:
Excessive potassium -> decreases excitability, cardiac arrythmia, muscle pain.
Low potassium -> muscle cramp (hyperaldosteronism)

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4
Q

What could cause hyperkalaemia (3 causes)

A
  1. Kidney’s inability to excrete K+
  2. ICF/ECF shifts: cell lysis
  3. Hormone deficiency: aldosterone insufficiency (low cell intake)

maybe intake + renal.

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5
Q

Hypokalemia causes

A
  1. hormone: high aldosterone levels (cell uptake)
  2. diarrhoea
  3. diuretics
  4. alcoholism (insufficient intake)
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6
Q

What could severe diarrhoea lead to (3 losses):

A

Loss of:
Water, Potassium, Bicarbonate
Lead to:
Loss of blood volume: sodium reabsorption, reduced GFR
Loss of potassium: potassium reabsorption from urine
Loss of bicarbonate: acidosis

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7
Q

Significance of ECF volume

A

Regulate blood pressure

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8
Q

Significance of ECF osmolarity

A

prevent cell shrinkage and swelling

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9
Q

what system regulates ECF volume

A

Renin-Angiotensin System-> Aldosterone
Sodium reabsorption/Excretion

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10
Q

what regulates ECF osmolarity

A

Water balance -> regulated by ADH
antidiuretic hormone (ADH) -> increase urine concentration (retain water)
no ADH -> dilute urine

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11
Q

SYNDROME OF INAPPROPRIATE ADH (what is an example)

A

1 example: Smoker -> lung tumour
The tumour produces ADH which leads to water retention + sodium dilution.
Other examples: Malignancies, cerebral pathologies, drugs

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12
Q

what is hypotonicity (concentration of sodium)

A

low osmolarity (low plasma sodium conc) -> water enter cells swell

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13
Q

what could hypotonicity cause

A

cerebral oedema

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14
Q

What is osmotic demyelination syndrome

A

Neurological disorder: too rapid compensatory response to hyponatraemia (low sodium in blood) - hypotonicity:
When ECF concentration gets lower than brain cell ICF during correction, cells shrink.

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15
Q

hypovolaemia (low BP) sensed by kidney

A

RAAS is activated, salt reclaimed -> increase ECF.

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16
Q

high BP sensed by kidney

A

RAAS is suppressed, salt wasted -> decrease ECF.

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17
Q

oedema and effective circulating volume

A

example 1: cardiac failure, high hydrostatic pressure
example 2: nephrotic syndrome, protein loss, low oncotic pressure
ECF expand leads to oedema.
But the body is still increasing sodium reabsorption due to the low effective circulating volume.

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18
Q

what causes low sodium levels (hyponatraemia)

A
  1. SIADH: water retention.
  2. renal failure
  3. Oedema
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19
Q

What could lead to high sodium (hypernatraemia)

A
  1. dehydration (water intake)
  2. dehydration due to diabetes insipidus (polyuria)
20
Q

what are some analytes (examples)

A

drugs, hormones, electrolyte

21
Q

specificity compared between mass spectrometry and immunoassay

A

mass spectrometry can be more specific when the antibody for immunoassays is lacking selectivity.

22
Q

disadvantage of MS (mass spec.)

A

It is less accessible

23
Q

Bland Altman Plot

A

different between the results of 2 assays

24
Q

Bland Altman Plot when low concentration

A

More variability

25
Q

C

Comparing MS and immunoassay in Bland Altman Plot

A

When immunoassay reading is always higher than MS, then there could be cross-reactivity.

26
Q

Problem with testosterone with immunoassay

A

the antibody cross-reacts to DHEAS, therefore a higher reading in the plot

27
Q

2 Main types of Mass Spec.

A

Gas chromatography - MS
Liquid chromatography - MS

28
Q

Separation during Gas Chroma. - MS

A

When the analytes separate on volatility/boiling point.

29
Q

Separation during Liquid Chroma. - MS

A

Separation according to partition coefficient:
partition coefficient: conc in oily vs conc in aqueous phase.

30
Q

Column Chromatography mechanism

A

Stationary Phase and Mobile Phase, analytes on MP will move at different speeds.

31
Q

High performance Liquid Chroma. (HPLC)

A

Stationary phase: Polarity changes
silica backbone and different chemical groups bound.

32
Q

how to ionise volatile, small molecules?

A

through electron impact.

33
Q

electron impact ionisation

A

e- impact will ionise and fragment most organic molecules.
The ion fragments will show up as different peaks on mass spectrum.

34
Q

When is electron spray used?

A

bigger compounds (peptides…)
molecules have readily-ionisable groups

35
Q

how is electron spray used

A
  • Put molecule of interest in a charged liquid phase
  • evaporate the liquid phase, only molecule of interest will be left charged.
36
Q

limitation of electron spray ionisation

A

There will be fewer fragment ions compared to gas.
Molecule picks up multiple charges -> difficult interpretation for m/z ratio.

37
Q

What is used in the final detection?

A

Single/Triple Quadruples

38
Q

Single Quadruple

A

4 Poles with Adjustable charge:
the selected ion will have a stable trajectory to the detector
limited mass range (max 1000 m/z)

39
Q

Triple Quadruple (steps)

A

first Q: selects precursor ions from sample.
second Q: collision with a gas to the ions, fragments to smaller ions.
third Q: the final/product ion will be selected.

40
Q

what is a matrix

A

has background noise: solvent, other impurities

41
Q

MS-MS compared to MS

A

better selectivity, less preparation, reduce background noise.
BUT: less accessible, expensive.

42
Q

what is the important characteristic of the internal standard

A

should be an isotopomer of the analyte, should have similar chemical characteristics.
to behave similarly during separation, ionisation etc.

43
Q

when is qualitative analysis used?

A

In drug abuse.
toxic metabolites of drugs.

43
Q

example with inborn error metabolites

A

enzyme dysfunction: disporportionate products (steroids: aldosterone, cortisol, oestradiol…)

43
Q

example with exogenous and endogenous testosterone

A

1.drug abuse: testosterone/epi-testosterone >6.
2. the exogenous testosterone from plants also has less C13 than human produced. (C13:12 ratio)

CBE (16 decks)

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