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2.2 Clinical Chemistry > Practical 2: Investigation of Total Protein and Albumin > Flashcards

Practical 2: Investigation of Total Protein and Albumin Flashcards

1
Q

What sample do we use when measuring proteins?

A

Serum

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2
Q

What is serum

A

The fluid that remains after plasma has clotted

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3
Q

Why is it important to note that serum is the fluid that remains after plasma has clotted?

A

It means fibrinogen and most of the clotting factors have been removed

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4
Q

Why do we measure proteins?

A

They give us a general insight into a person’s health

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5
Q

What plasma proteins are not synthesised in the liver?
(3)

A

Immunoglobulins

Haemoglobin

Hormonal proteins

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6
Q

What are the roles of plasma proteins?
(8)

A

Transport

Enzyme catalysis

Homeostatic control

Hormonal regulation

Blood coagulation

Immunity

Growth and repair

Heredity

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7
Q

Why would calcium levels be measured
(3)

A

To screen/monitor for bone diseases

To screen/monitor for diseases of the parathyroid gland

To screen/monitor for diseases of the kidney

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8
Q

What is free/ionised calcium?

A

Calcium not attached to proteins in the blood

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9
Q

What percentage of calcium in the blood is attached to proteins

A

About 50%

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10
Q

What is corrected calcium concentration?

A

An estimate of the total concentration of calcium as if the albumin concentration was normal

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11
Q

Why is a corrected calcium concentration needed?
(3)

A

50% of calcium in the blood is bound to plasma proteins

The majority of protein in plasma is albumin

A low albumin would give a low calcium concentration however this doesn’t accurately reflect the calcium concentration i.e. it might not actually be low

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12
Q

How does corrected calcium concentration work?

A

For every 1g/L that the albumin concentration is below the mean, the calcium concentration is 0.02 mmol/L below what it would be if the albumin concentration was normal

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13
Q

What method is used to measure total protein

A

Biuret

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14
Q

What does a total serum protein test measure
(2)

A

The total amount of protein in the blood

The amounts of albumin and globulin in the blood

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15
Q

Why are total serum protein tests carried out?

A

They are used in the diagnosis and treatment of a variety of diseases involving the liver, kidney and bone marrow as well as other metabolic or nutritional disorders

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16
Q

What is the principle behind the Biuret method of measuring total serum protein
(3)

A

Cupric ions (copper ions) in an alkaline solution react with the peptide bonds of proteins and polypeptides containing at least two peptide bonds

This react produces a violet coloured complex

The absorbance of this complex at 546nm is directly proportional to the concentration of the protein in the sample

17
Q

What absorbance is the biuret reagent read at

A

546nm

18
Q

What colour is the polypeptide-biuret complex?

A

Violet

19
Q

How must a blood sample be collected and prepared for the total serum protein test
(4)

A

Sample = serum, heparinized plasma or EDTA plasma

Normal procedures for collecting and storing serum

Serum will be stable for 3 days between 2+ and +8 degrees Celsius

Serum will be stable for 6 months at -20 degrees Celsius

20
Q

At what temperature should a total serum protein test be carried out at

A

Room temperature or 37 degrees

21
Q

What is your blank for the total serum protein test?

A

Water

22
Q

How many standards should you use for the total serum protein test

A

Three

23
Q

How many controls should you use for the total serum protein test

A

2

24
Q

How much incubation is needed for the total serum protein test

A

20 minutes before reading absorbance

25
Q

What method of calculations is needed to determine the concentration of protein in your sample

A

Unitary method

26
Q

What is the equation for the unitary method

A

(Absorbance of sample/Absorbance of standard) x Concentration of standard

27
Q

What method is used to determine the concentration of albumin?

A

Bromocresol Green Method

28
Q

Albumin makes up what percentage of total protein

A

Between 55 and 65%

29
Q

How long is the half life of albumin

A

2 to 3 weeks

30
Q

What are the functions of albumin?
(3)

A

To maintain the water balance in serum and plasma

To transport and store a wide variety of ligands e.g. fatty acids, calcium, bilirubin and hormones such as thyroxine

To provide an endogenous source of amino acids

31
Q

What is hypoalbuminaemia associated with?
(7)

A

Analbuminaemia

Impaired albumin synthesis in the liver

Livre disease

Malnutrition or malabsorption

Generalised shock

Burns or dermatitis

Kidney disease and intestinal disease

32
Q

What is hyperalbuminaemia associated with?

A

Little diagnostic relevance except perhaps dehydration

33
Q

What is the principle behind the Bromocresol green method of determining albumin concentration?
(3)

A

Its based on the quantitative binding of albumin to the indicator bromocresol green

The albumin-BCG-complex absorbs maximally at ~600nm (630nm)

The absorbance is directly proportional to the concentration of albumin in the sample

34
Q

How should a sample be prepared and collected for BCG test?

A

The same as for total serum protein

35
Q

At what absorbance do you measure the albumin concentration

A

630nm

36
Q

What blank is used for the albumin concentration

A

Water and reagent blank

37
Q

For how long do you incubate the albumin test

A

10 mins at 20->25 degrees Celsius

38
Q

How do you calculate the albumin concentration from your absorbances

A

Unitary method

39
Q

How do you calculate total globulins?

A

Total protein-albumin
i.e. everything other than albumin (fibrinogen not included as serum is the liquid part of clotted blood)

2.2 Clinical Chemistry (28 decks)

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