knowledge questions Flashcards
Explain the principles of quality control in a clinical lab.
Quality control ensures accuracy and reliability of lab results. It involves regular calibration of equipment, using control samples to verify procedures, and maintaining proper documentation. Deviations from expected results prompt immediate corrective actions to minimize errors.
Describe the process of Gram staining and its clinical relevance.
Gram staining differentiates bacteria based on their cell wall structure. The process involves applying crystal violet dye, iodine, alcohol for decolorization, and safranin.
Gram-positive bacteria: the violet color
Gram-negative: red/pink. This technique guides antibiotic treatment by identifying bacterial types.
Relation to Antibiotics:
Gram-positive bacteria are often more susceptible to beta-lactams (e.g., penicillins).
Gram-negative bacteria may be resistant due to their outer membrane acting as a barrier.
prokaryotic vs eukaryotic
Prokaryotic Cells:
No nucleus; DNA is in a nucleoid region.
Lack membrane-bound organelles.
Typically smaller and simpler (e.g., bacteria).
Eukaryotic Cells:
Contain a nucleus with DNA.
Have membrane-bound organelles (e.g., mitochondria, ER).
Found in plants, animals, fungi, and protists.
How do you calculate the concentration of a solution using a spectrophotometer?
Use the Beer-Lambert Law: A = εlc where:
A is absorbance,
ε is the molar extinction coefficient,
l is the path length (usually 1 cm), and
c is the concentration.
2.Measure the absorbance of the sample at the desired wavelength.
3.Use the equation (or a standard curve) to calculate the concentration.
purpose + process of aseptic techique
Purpose: Prevent contamination of samples, reagents, and lab equipment.
Process:
1. Disinfect work surfaces before and after experiments.
2.Work near a Bunsen burner flame to maintain sterile conditions.
3.Use sterilized instruments and handle materials carefully to avoid introducing contaminants.
importance of using controls in an experiment?
Controls provide a baseline for comparison, ensuring that observed changes in the experiment are due to the variable being tested.
Positive Control: Confirms the experiment works as expected.
Negative Control: Ensures no unintended effects occur when the variable isn’t present.
how to prepare a buffer solution
- Calculate the amounts of acid/base and salts needed using the Henderson-Hasselbalch equation:
pH = pKa + log([A⁻]/[HA]).
2.Dissolve the components in distilled water.
3.Adjust the pH using a pH meter and small amounts of acid or base.
4.Dilute to the desired volume with distilled water.
principle of centrifugation
-separates components of mixture based on their size, shape, and density by applying centrifugal force
heavier object: bottom (pellet)
ligher object: remain in the supernatant
influencing factors:
rotor speed
radius
time
PCR
amplifies DNA through:
Denaturation: Heating the sample to separate DNA strands (~95°C).
Annealing: Cooling to allow primers to bind to target sequences (~50-65°C).
Extension: DNA polymerase synthesizes new DNA strands (~72°C).
These steps are repeated for 20-40 cycles to generate millions of copies of DNA.
What is the difference between accuracy and precision in measurements?
Accuracy: How close a measurement is to the true value.
Precision: How consistent repeated measurements are with each other, regardless of their accuracy.
What is the purpose of using a blank in spectrophotometry?
The blank contains all components of the sample except the analyte being measured. It sets the baseline absorbance to zero, correcting for any absorbance caused by solvents or reagents.
shapes + types of bacteria
cocci: spherical
bacilli: rod-shaped
spirilla: spiral
vibrio: comma-shaped
spirochetes: corkscrew-shaped
di: pairs
strep: chains
staph: clusters
palisades/ v shaped: bacilli aligned side by side
