BIOCHEMISTRY PRACTICAL 1 (CREATINE IN URINE) Flashcards
WHAT IS CREATININE?
heterocyclic substance containing nitrogen
-anhydride of creatine
-waste product of muscle energy metabolism with urine
WHAT IS CREATINE?
a substance formed from the amino acids Gly, Arg, Met
-a source of energy for the muscle contraction - in the muscle it is found in a phosphorylated form as a creatine phosphate, i.e. it is one of energy rich compounds from which ATP can be generated
IS THE AMOUNT OF CREATINE PER UNIT OF MUSCLE MASS CONSTANT?
yes
-thus the spontaneous breakdown is also
constant: creatinine is released from the muscles into blood at a relatively constant rate
-blood concentration and excretion are very stable
WHAT IS A DIRECT REFLECTION OF LEAN MUSCLE MASS?
serum creatinine levels
WHAT IS A MARKER OF KIDNEY DAMAGE?
increased serum concentration of creatinine
WHAT ARE URINE CREATININE TESTS USED FOR IN MEDICINE?
A: estimation of the glomerular filtration rate
B: evaluation of urine dilution
C: standardization of excretion of other substances found in the urine
WHAT ANALYTICAL METHOD IS USED TO MEASURE THE CONCENTRATION OF CREATININE?
spectrophotometry
WHAT IS THE SOURCE OF ELECTROMAGNIFICATION IN A SPECTROPHOTOMETER?
hydrogen or deuterium lamp (UV)
tungsten lamp (VL)
WHAT IS UV RANGE OF ELECTROMAGNETIC RADIATION USED FOR?
If the analyzed solution in the cuvette is colourless
-UV = 190 - 400 nm)
WHAT IS THE VISIBLE RANGE OF ELECTROMAGNETIC RADIATION USED FOR?
If the analyzed solution of the cuvette is colourful
-VIS, = 400 - 700 nm
HOW DO ABSORBED COLOURS AND COMPLEMENTARY COLOURS WORK?
a specific colour is absorbed but a colour complementary to this one will be shown as the solutions colour
WHAT METHOD IS USED FOR THE DETERMINATION OF CREATININE (colourless)?
Jaffe’s reaction: creatinine reacts in alkaline solution with picric acid, red-orange product is produced.
-A concentration of the product is proportional to the concentration of the creatinine in a sample.
WHAT DOES SPECIFIC WAVELENGTH MEAN?
Each compound can absorb a radiation of a discrete energy
WHAT ARE CHROMOPHORES?
the structures of the compound able to absorb the radiation
WHAT IS MONOCHROMATIC RADIATION?
radiation of a discrete wavelength
WHICH IS LOWER I0 OR I?
The intensity of the transmitted radiant
energy (I) will be lower than an original intensity (I0).
WHAT IS USED TO CALIBRATE THE THE SPECTROPHOTOMETER?
-blank solution of distilled water
-having the same composition as the analyzed sample except the compound of interest, e.g. creatinine
WHAT DOES THE TRANSMITTANCE VALUE OF 1 MEAN?
1 is related to the solution which does not absorb any part of the radiation
WHAT DOES THE TRANSMITTANCE VALUE OF 0 MEAN?
(the value 0 is found if all incident
radiation is absorbed in the cuvette
ABORBANCE AND TRANSMITANCE
higher values of the absorbance are associated with very low values of the transmittance
WHAT IS THE RELATIONSHIP BETWEEN ABSORBANCE AND CONCENTRATION?
linear
WHAT IS THE RELATIONSHIP BETWEEN TRANSMITTANCE AND CONCENTRATION?
exponential
WHAT IS A MONOCHROMATOR?
prism which selects the wavelength
WHAT ARE THE PARTS OF A SPECTROPHOTOMETER?
light source
lens
monochromator
sample in cuvette
detector
WHAT IS A STANDARD SOLUTION?
a solution with a known concentration
WHAT IS ABSORBANCE?
measure of the capacity of a substance to absorb light of a specified wavelength
WHAT ARE THE WAVELENGTHS OF VISIBLE LIGHT?
approximately 400 to 700 nm
WHAT IS THE NORMAL RANGE OF CREATININE IN URINE?
creatinine in urine 5.7 – 14.7 mmol/l
WHAT IS TRANSMITTANCE?
how much light passes through a sample unchanged
WHAT IS THE RELATIONSHIP BETWEEN ABSORBANCE AND TRANSMITTANCE?
A = -log T
WHAT ARE CUVETTES MADE FROM?
quartz
plastic
transparent glass (not for UV)
WHAT IS THE BEER LAMBERT LAW?
path length and concentration of a chemical are directly proportional to its absorption of light
WHAT IS THE CALIBRATION CURVE?
determines the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration
WHAT IS THE PRINCIPLE OF THE SPECTROPHOTOMETRY?
measuring the absorption spectrum of a compound, that is, the absorption of light by a solution at each wavelength.
WHAT IS MOLAR CONCENTRATION?
moles of solute per litre of solution
WHAT IS MASS CONCENTRATION?
mass of solute present in a given volume of a solution
WHAT IS MOLAR MASS?
mass per mole of a substance
Cus / Aus = Cst / Ast
