BIOCHEMISTRY IMPORTANT LONG QUESTIONS
AS PER PREVIOUS YEAR QUESTIONS
DMLT, 2ND YEAR
1.
ENUMERATE THE
LABORATORY TESTS TO DETECT UROBILINOGEN AND URINARY BILE SALTS.
Laboratory Tests to Detect Urinary
Urobilinogen and Bile Salts
URINARY UROBILINOGEN TEST
- Purpose:
This test is performed to measure the levels of urobilinogen in urine. Changes in urobilinogen levels can indicate conditions like: - Increased
Urobilinogen: Seen in liver dysfunction (e.g., hepatitis,
cirrhosis) or excessive breakdown of red blood cells (hemolysis).
- Decreased
Urobilinogen: May occur in biliary obstruction,
where bile flow is blocked.
- Test
Methods:
a. Ehrlich’s
Test:
i. Principle:
Urobilinogen reacts with Ehrlich’s
reagent (p-dimethyl amino benzaldehyde), producing a red or pink colour.
ii. Procedure:
1. A
few drops of Ehrlich’s reagent are added to the urine sample.
2. Observe
the colour change; the intensity of the red or pink indicates the amount of
urobilinogen.
b. Dipstick
Method:
i. Principle:
A chemical strip added
with reagents
reacts with urobilinogen in urine.
ii. Procedure:
1. Dip
the test strip into a fresh urine sample.
2. After
a few seconds, compare the colour
change on the strip to the reference chart provided.
iii. Advantage:
Quick, easy, and widely used in clinical settings.
URINARY BILE SALTS TEST
- Purpose:
This test detects the presence of bile salts in urine. Normally, bile salts are absent in urine. Their presence indicates: - Biliary
obstruction (e.g., gallstones, tumors blocking
bile flow).
- Liver
diseases like hepatitis or cirrhosis.
- Test
Method:
Hay’s Test: - Principle:
Bile salts reduce the surface tension of urine. When sulfur powder is sprinkled on the surface of the urine: - If
bile salts are present: The sulfur
powder sinks due to reduced surface tension.
- If
bile salts are absent: The sulfur
powder floats.
- Procedure:
- Collect
a fresh urine sample in a clean container.
- Gently
sprinkle a small amount of sulfur powder on the urine's surface.
- Observe
whether the sulfur sinks or floats.
2.
WRITE DIFFERENT
FUNCTIONS OF THE KIDNEY. CLASSIFY DIFFERENT RENAL FUNCTION TESTS. BRIEFLY WRITE
ABOUT THE GLOMERULAR FILTRATION RATE.
DIFFERENT FUNCTIONS OF THE KIDNEYS ARE:
i.
Removing Waste:
Filters blood to
excrete waste in urine.
ii.
Balancing Fluids:
Maintains water and
electrolytes like sodium and potassium.
iii.
Regulating Blood Pressure:
Produces renin to
control blood pressure.
iv.
Boosting Red Blood Cells:
Makes erythropoietin
to form red blood cells.
v.
Controlling pH:
Maintains blood pH balance by managing acids and bases.
RENAL FUNCTION TESTS:
These are tests to check how well kidneys are working.
i.
BUN Test (Blood Urea Nitrogen):
Measures the level of urea
nitrogen in blood,
reflecting how well kidneys are filtering waste products. Normal range: 7-20
mg/dL. Elevated
levels may indicate kidney dysfunction or dehydration.
ii.
Creatinine Test:
Assesses the level of
creatinine in blood, indicating how efficiently kidneys are removing
waste products. Normal range: 0.6-1.2 mg/dL for adult males, 0.5-1.1 mg/dL for
adult females. Elevated
levels can suggest kidney dysfunction.
iii.
GFR Test (Glomerular Filtration Rate):
Determines how effectively your kidneys are filtering waste from the blood per
minute. Normal range:
Above 120 mL/min. A lower GFR may indicate kidney damage or dysfunction.
iv.
Urine Analysis:
· Visual
Colour and Clarity: Observes the colour and clarity of urine, which can
indicate hydration status and potential health issues. Normal colour: Pale yellow to amber; normal
clarity: Clear.
· Dipstick
Test: Uses a chemical strip
to detect abnormalities in urine, such as the presence of blood, protein, glucose, ketones, bilirubin, and nitrites. Abnormal
results may suggest various kidney or urinary tract conditions.
· Microscopic
Examination: Examines urine sediment under a microscope to detect cells, crystals, bacteria, or other substances not
visible to the naked eye. Normal findings include few to no red blood cells,
white blood cells, epithelial cells, and crystals.
v.
Kidney Imaging Test (CT/MRI):
Imaging techniques used to visualize the kidneys and
surrounding structures. These tests can identify abnormalities such as
tumors, cysts, or kidney stones that may affect kidney function.
GLOMERULAR
FILTRATION RATE:
I.
Definition:
Glomerular Filtration Rate (GFR) measures how efficiently the kidneys filter
blood, removing waste and excess fluids.
II.
Normal Rate:
A healthy GFR is usually 120
mL/min, but it can vary based on age, gender, and body size.
III.
Clinical Use:
GFR is used to diagnose, monitor, and evaluate the severity of kidney diseases.
3.
WHAT ARE THE FUNCTIONS
OF THE LIVER? CLASSIFY DIFFERENT LIVER FUNCTION TESTS. WHAT ARE THE INDICATIONS
OF LIVER FUNCTION TESTS?
DIFFERENT FUNCTIONS OF THE LIVER:
a.
Detoxification:
Removes toxins and harmful
substances from the blood.
b.
Metabolism:
Processes carbohydrates,
fats, and proteins for energy.
c.
Bile Production:
Produces bile to
aid in fat digestion.
d.
Storage:
Stores vitamins, minerals, and glycogen for energy.
e.
Blood Clotting:
Produces proteins (clotting
factors) essential for blood clotting.
LIVER FUNCTION TESTS:
Liver function tests (LFTs) are blood tests that assess
liver health. They help diagnose and monitor liver diseases like hepatitis and
cirrhosis. Here are the common LFTs:
a.
ALT (Alanine aminotransferase):
Found mainly in the liver. Elevated
levels indicate liver
damage. Normal range: 7-56 U/L for men, 5-44 U/L for women.
b.
AST (Aspartate aminotransferase):
Another liver enzyme. Elevated
levels can signal liver
damage or heart/muscle issues. Normal range: 8-48 U/L for men, 7-35 U/L
for women.
c.
ALP (Alkaline phosphatase):
Found in many tissues including the gall bladder. High
levels can indicate bile
duct blockage. Normal range: 45-115 U/L for adults.
d.
Bilirubin:
Waste product from red blood cell breakdown. High levels suggest liver issues. Normal range: 0.1-1.2 mg/dL.
e.
Albumin:
Liver-produced protein. Low
levels can indicate liver
damage. Normal range: 3.5-5.5 g/dL.
f.
PT (Prothrombin time):
Measures blood clotting
time. An abnormal
PT suggests liver
disease.
INDICATION OF LIVER FUNCTION TESTS:
a.
Diagnosing Liver Diseases:
To detect conditions like hepatitis, or fatty liver.
b.
Monitoring Liver Health:
To check liver function in chronic
diseases or after
surgery.
c.
Assessing Medication Effects:
To evaluate potential
liver damage from drugs.
d.
Screening in High-Risk Individuals:
For those with alcohol use,
obesity, or viral infections.
4.
ENUMERATE DIFFERENT
THYROID FUNCTION TESTS. WRITE BRIEFLY ABOUT THE ABNORMALITIES OF THYROID
FUNCTION LIKE HYPERTHYROIDISM AND HYPOTHYROIDISM.
Thyroid function
tests are a group of blood
tests used to
assess the health and activity of the thyroid gland, which is a small
butterfly-shaped gland located in the front of your neck.
The most common
thyroid function tests include:
a)
Thyroid
Stimulating Hormone (TSH):
TSH is produced by the pituitary
gland and stimulates the thyroid gland to produce thyroid hormones (T3 and T4). High TSH levels indicate
an underactive thyroid
(hypothyroidism), while low TSH levels suggest an overactive thyroid
(hyperthyroidism).
b)
Free
Thyroxine (FT4) and Total Thyroxine (T4): T4 is the main thyroid hormone produced by the
thyroid gland. Free T4
(FT4) represents the active,
unbound form of T4, and total T4 includes both the active and bound forms. These tests
help evaluate thyroid hormone levels and can aid in diagnosing thyroid
disorders.
c)
Free
Triiodothyronine (FT3) and Total Triiodothyronine (T3): T3 is another thyroid hormone that is more potent but
produced in smaller quantities compared to T4. Free T3 (FT3) measures the unbound
form of T3, while total T3 includes both active and bound forms.
d)
Thyroid
Antibodies: These tests
are used to detect
antibodies that may
attack the thyroid gland, leading to autoimmune thyroid disorders like Hashimoto's
thyroiditis or Graves' disease.
e)
Thyroglobulin: Thyroglobulin is a protein produced by the thyroid
gland and is used as a marker
for certain thyroid conditions, including thyroid cancer.
f) Thyroid Ultrasound: In addition to blood tests, a thyroid ultrasound is a
non-invasive imaging test used to visualize the thyroid gland's size, shape, and structure. It helps
identify any abnormalities.
HYPERHTYROIDISM
Definition:
A condition where the thyroid gland produces too much thyroid hormone.
Types:
a)
Graves’ Disease:
An autoimmune condition causing excess hormone production.
b)
Goiter:
Enlarged thyroid with hormone-secreting nodules.
c)
Thyroiditis:
Inflammation causing temporary hormone release.
Symptoms: Weight loss,
rapid heartbeat, sweating, and nervousness.
HYPOTHYROIDISM
Definition:
A condition where the thyroid gland produces too little thyroid hormone, slowing metabolism.
Types:
i.
Hashimoto’s Disease:
An autoimmune disorder causing thyroid damage.
ii.
Iodine Deficiency:
Insufficient iodine intake reduces hormone production.
iii.
Congenital Hypothyroidism:
Present at birth due to thyroid development issues.
5.
DESCRIBE DIABETES
MELITUS. WHAT DO YOU MEAN BY GTT? DESCRIBE DETAILS OF GTT.
Diabetes mellitus, commonly referred to as diabetes,
is a chronic metabolic disorder characterized by high
blood glucose levels (hyperglycemia)
resulting from the body's inability to produce
enough insulin or use it effectively. Insulin is a hormone produced by beta cells of pancreas that regulates
blood sugar levels by helping glucose enter cells to be used for energy.
TYPES:
TYPE I
In Type 1 diabetes, the immune system mistakenly attacks and destroys the
insulin-producing beta cells in the pancreas, leading to:
- Little or no insulin production
- Elevated blood glucose levels
- Cells cannot take up glucose for energy
- Increased hunger and thirst
- Frequent urination
- Fatigue and weakness
- Blurred vision
TPYE II
In Type 2 diabetes, the body
becomes resistant to insulin and/or the pancreas
fails to produce enough insulin to meet the body's needs. The insulin
receptor on cells may also become damaged, leading to further insulin
resistance and impaired glucose uptake by cells.
GTT
GLUCOSE TOLERANCEC TEST
Purpose:
To assess how the body processes glucose,
often for diagnosing diabetes or gestational diabetes.
Patient Preparation
a)
Fasting:
Avoid food and drinks (except water) for 8–12 hours
before the test.
b)
Medications:
Follow your doctor’s advice about stopping any medicines that affect blood sugar.
c)
Activity: Avoid strenuous exercise before the test.
d)
Inform Your Doctor:
Share details about your medicines, medical conditions, or recent
illnesses.
Procedure
a)
Baseline Sample:
A fasting blood sample is taken first.
b)
Glucose Drink:
You’ll drink a solution with a set amount of glucose (usually
75 g).
c)
Wait Period:
Rest for 2 hours without eating, drinking,
or strenuous activity.
d) Blood
Samples: Blood is drawn at regular intervals (e.g., every 30 minutes) to monitor glucose levels.
e)
Review Results:
Your doctor will analyze and explain your
test results.
Reference Range
- Fasting
Glucose: Normal is less than 110 mg/dL.
- 2-Hour
Glucose:
- Normal:
<140 mg/dL
- Prediabetes:
140–199 mg/dL
- Diabetes:
≥200 mg/dL
6.
WHAT DO YOU MEAN BY
AUTOMATION IN A BIOCHEMISTRY LABORATORY? DESCRIBE THE ADVANTAGES AND THE
DISADVANTAGES.
An auto analyzer, also known as an automated analyzer or automated
chemistry analyzer, is a sophisticated laboratory
instrument used in clinical and analytical
chemistry to perform a wide range of
chemical tests and analyses on biological samples such as blood, urine, and
other bodily fluids.
These analyzers are designed to automate the
process of sample handling, preparation, and analysis, offering several
advantages over manual or semi- automated methods.
ADVANTAGES
a) High
Throughput: Auto
analyzers are capable of processing a large number
of samples in a relatively short amount of time. This high throughput is
especially valuable in clinical laboratories where a large volume of patient
samples need to be analyzed quickly.
b) Time
Efficiency: Automation
significantly reduces the time required for sample
analysis. Sample handling, pipetting, mixing, incubation, and
measurement are all carried out automatically, eliminating human error and
speeding up the testing process.
c) Reduced
Labor Costs: By automating
routine and repetitive tasks, auto analyzers reduce
the need for manual labor. This not only lowers labor costs but also
minimizes the risk of human error, leading to more accurate results.
d) Sample
Preservation: Auto
analyzers are designed to handle and store samples
under controlled conditions, ensuring sample integrity and minimizing
the risk of contamination or degradation. This is crucial for maintaining the
quality of samples, especially in clinical diagnostics.
e) 24/7
Operation: Many auto
analyzers are capable of continuous operation, allowing laboratories to run
tests around the clock without the need for constant human supervision. This is
particularly beneficial for urgent or time-sensitive testing requirements.
f)
Data Management: Auto analyzers are equipped with sophisticated data
management systems that capture and store test results digitally.
DISADVANTAGES
a)
Initial Cost: Auto analyzers are typically expensive
to purchase and install. The initial investment can be a significant
barrier for smaller laboratories or healthcare facilities with limited budgets.
b) Maintenance
Cost: These complex
instruments require regular maintenance and
calibration to ensure accurate and reliable results. Maintenance costs can add
up over time, including the cost of replacement parts and technician salaries.
c) Complexity:
Auto analyzers are
sophisticated instruments that require skilled
personnel to operate and maintain. Training and expertise are essential
to troubleshoot issues and perform necessary repairs.
d) Sample
Volume Requirement: Some
auto analyzers may have minimum sample volume
requirements, which can be a limitation when dealing with limited or
precious samples. In some cases, this may lead to sample wastage.
e) Dependency
on Power: Auto analyzers
rely on a stable and uninterrupted power supply.
Power outages or fluctuations can disrupt operations, potentially leading to
sample loss and downtime.
7.
DESCRIBE THE PRINCIPLE OF COLORIMETER. MENTION ITS ADVANTAGES AND
DISADVANTAGES.
Purpose: Measures the concentration of a substance in a solution by
analyzing colour intensity based on the Beer-Lambert Law.
Principle:
- Light of a specific
wavelength passes through the solution.
- The
substance absorbs light proportionally
to its concentration.
- Absorbance is used to calculate the substance's concentration.
Instrumentation:
a)
Light Source:
Emits visible light (e.g., LED, tungsten lamp).
b)
Sample Chamber: Holds the solution in a cuvette.
c)
Wavelength Selector:
Filters light to the desired wavelength.
d)
Photodetector: Measures light passing through the sample and
converts it to an electrical signal.
e)
Display:
Shows absorbance or concentration value.
Uses:
a)
Chemical Analysis:
Measures ion or compound concentrations.
b)
Clinical Chemistry:
Analyzes blood, urine, or serum for diagnostics.
c)
Environmental Analysis:
Detects pollutants in water or soil.
d)
Food Industry:
Ensures quality control of sugars, vitamins, or preservatives.
Advantages:
- Accuracy:
Provides reliable concentration measurements.
- Ease
of Use: Simple operation and quick results.
- Cost-Effective:
Affordable for routine lab analyses.
Disadvantages:
- Limited
Range: Can only analyze coloured solutions.
- Interference:
Impurities or multiple absorbing substances can affect accuracy.
- Light
Source Dependence: Requires stable and appropriate
light wavelengths.
8.
WHAT IS CSF? DESCRIBE
IN BRIEF REGARDING THE SAMPLE COLLECTION. DESCRIBE THE BIOCHEMICAL TESTS
PERFORMED.
CSF:
CSF is a clear, colourless fluid
that surrounds the brain and spinal cord, serving several crucial
functions, including protection, support, and nutrient supply to
the central nervous system (CNS).
CSF SAMPLE COLLECTION:
CSF is collected through a procedure called lumbar
puncture.
The steps are as follows:
·
Preparation:
The patient lies on their side or sits up, bending forward to expose the lower
back.
·
Site Cleaning:
The lower back is cleaned, and a local anaesthetic is applied.
·
Needle Insertion:
A sterile needle is inserted between the vertebrae, usually between L3 and L4,
to access the spinal canal.
·
CSF Collection:
A small amount of CSF is withdrawn into sterile tubes for analysis.
TESTS:
CSF function tests are commonly performed to help
diagnose various neurological disorders, infections, and inflammatory
conditions affecting the CNS. The most common CSF function tests include:
a)
Cell Count and Differential:
This test examines the number and type of cells present in the CSF. An elevated white blood cell count may indicate infection or inflammation, while an increased number of red blood cells may suggest bleeding in the CNS.
b)
Protein Content:
Elevated protein levels can be a sign of inflammation, infection,
or certain neurological conditions.
c)
Glucose Level:
CSF glucose levels are compared to blood glucose levels. A decreased CSF glucose level relative to blood
glucose may indicate bacterial or fungal meningitis.
d)
Lactate Level:
Elevated lactate levels in CSF can be a
marker of bacterial or viral infections of
the CNS.
e)
Opening Pressure:
This measures the pressure of the CSF within the spinal canal. High pressure can be indicative of conditions such
as hydrocephalus (a condition where CSF builds up around the brain).
f)
Viral PCR (Polymerase Chain Reaction):
This test detects the presence of viral DNA or RNA in the CSF.
9.
ENUMERATE THE CAUSES OF
JAUNDICE AND DISCUSS VARIOUS LIVER FUNCTION TESTS.
CAUSES OF JAUNDICE:
Jaundice occurs when there is an excess of bilirubin in the blood,
leading to yellowing of the skin and eyes.
Common causes include:
a)
Pre-Hepatic
Causes: Increased breakdown of red blood cells (e.g., hemolysis).
b)
Hepatic
Causes: Liver diseases affecting bilirubin metabolism. (liver normally
converts bilirubin into a water-soluble form for excretion via bile).
c)
Post-Hepatic
Causes: Obstruction of bile flow (because bile contains water-soluble
form of bilirubin).
VARIOUS
LIVER FUNCTION TESTS:
Already discussed in question no. 3.
10. DEFINE DIABETES MELITUS.
WHAT ARE TESTS USUALLY ADVISED FOR A DIABETES PATIENT? WRITE ABOUT GOD-POD
METHOD.
DIABETES MELITUS:
Already discussed in question no 5.
GOD-POD METHOD:
The GOD-POD method is a chemical assay that uses
enzymes (glucose oxidase and peroxidase) to convert glucose to hydrogen
peroxide, which then reacts with a chromogenic reagent to produce a coloured
compound. The intensity of the colour is proportional to the glucose concentration.
Procedure:
a)
Sample Preparation:
o Collect
a blood sample.
b)
Addition of Glucose Oxidase (GOD):
o Add
glucose oxidase solution to the blood sample. Glucose oxidase catalyzes the
conversion of glucose to hydrogen peroxide.
c)
Incubation:
o Incubate
the mixture at a specific temperature (usually 37°C) for a predetermined time
(typically 5-10 minutes).
d)
Addition of Peroxidase:
o Add
a known volume of a peroxidase solution and
a chromogen to the mixture.
e)
Incubation:
o Incubate
the mixture again at the same temperature for a specific time to ensure
complete reaction.
f)
Change of Colour:
o After
the second incubation, the reaction will produce a coloured compound. The colour
intensity is directly proportional to the amount of glucose in the sample.
g)
Colour Measurement Using
Spectrophotometer:
o Use
a spectrophotometer to measure the absorbance of the coloured solution at a
specific wavelength (typically around 540 nm).
h)
Result Reporting:
o Report
the glucose concentration in the sample in the appropriate units (e.g., mg/dL).
11. NAME THE VARIOUS TESTS IN LIPID PROFILE. DESCRIBE THE DETAILS OF
COLLECTION AND TESTING OF CHOLESTEROL.
Lipid Profile Tests
A lipid profile evaluates the lipid levels in the
blood to assess cardiovascular health. It typically includes the following
tests:
1.
Total Cholesterol:
Measures overall cholesterol levels in the blood.
2.
High-Density Lipoprotein (HDL):
Known as "good cholesterol"; helps remove excess cholesterol.
3.
Low-Density Lipoprotein (LDL):
Known as "bad cholesterol"; excess levels may lead to plaque buildup
in arteries.
4.
Triglycerides:
Measures fat stored in the body, high levels can increase the risk of heart
disease.
SPECIMEN COLLECTION
- Preparation:
a)
The patient should fast for 9-12 hours prior to the test to avoid postprandial
lipid changes.
b)
Avoid alcohol and
high-fat meals the night before.
- Procedure:
a)
A venous blood sample is drawn using a
sterile syringe and collected in a plain tube.
b)
The sample is allowed to clot and then
centrifuged to separate serum.
CHOLESTEROL TESTING
a)
Method:
o Enzymatic methods (e.g., Cholesterol
Oxidase-Peroxidase method) are commonly used.
b)
Procedure:
o Serum
is mixed with reagents that react with
cholesterol to produce a measurable colour change.
o The
intensity of the colour, measured using a spectrophotometer,
correlates with the cholesterol concentration.
c)
Reference Range:
o Desirable
total cholesterol: <200 mg/dL.
o Borderline
high: 200–239 mg/dL.
o High:
≥240 mg/dL.
Clinical Significance
- Elevated
cholesterol levels can indicate risk for atherosclerosis, coronary artery
disease, and stroke.