Answer: D. 4, 2, 3, 1

Explanation: The breakdown of erythrocytes begins with hemoglobin degradation (4), then formation of biliverdin (2), conversion to free bilirubin (3), and finally conjugation of bilirubin in the liver (1).

Answer: D. Peyer's patches

Explanation: Peyer's patches are lymphoid follicles found in the distal ileum. They play an important role in the immune surveillance of the gastrointestinal tract.

Answer: A. Inulin

Explanation: Inulin is used to measure glomerular filtration rate because it is freely filtered, neither reabsorbed nor secreted by the kidneys, providing an accurate index of renal function.

Answer: B. Anti-H antibodies

Explanation: Bombay blood group individuals produce anti-H antibodies in addition to anti-A and anti-B, making them incompatible with any regular blood group which expresses the H antigen.

Answer: C. enterochromaffin cells of the GI tract

Explanation: More than 90% of the body’s serotonin is found in the enterochromaffin cells of the gastrointestinal tract, where it regulates intestinal movements and other functions.

Answer: D. Structure and function of ribosome with X-ray crystallography

Explanation: The Nobel Prize in Medicine 2013 was awarded for determining the structure and function of the ribosome using X-ray crystallography, a breakthrough that advanced our understanding of protein synthesis.

Answer: C. Glomerular filtration rate

Explanation: Inulin clearance is the gold standard for measuring glomerular filtration rate because it is freely filtered at the glomerulus and neither reabsorbed nor secreted by the kidneys.

Answer: B. aspartyl protease

Explanation: The conversion of angiotensinogen to angiotensin I is catalyzed by renin, an aspartyl protease. This enzyme is a key component of the renin-angiotensin system that regulates blood pressure.

Answer: C. Eosinophils

Explanation: Eosinophils are known to increase in allergic conditions, such as asthma, and are involved in the inflammatory response associated with allergies.

Answer: C. Both A and B

Explanation: Both narcolepsy and sleep apnea are characterized by excessive daytime sleepiness. Narcolepsy is a neurological disorder while sleep apnea is a breathing disorder, yet both significantly impact sleep quality.

Answer: A. 4

Explanation: Hemoglobin, the oxygen-carrying protein in red blood cells, can bind to four oxygen molecules, one at each of its four heme groups. This enables efficient oxygen transport throughout the body.

Answer: A. The red blood cells

Explanation: Red blood cells lack nuclei and are primarily involved in oxygen transport. They do not participate in the immune response, unlike white blood cells which are central to immune system function.

Answer: C. 40S and 60S

Explanation: Eukaryotic ribosomes consist of a small 40S subunit and a large 60S subunit. This division is distinct from prokaryotic ribosomes, which are composed of 30S and 50S subunits, and is fundamental for protein synthesis in eukaryotic cells.

Answer: A. Poorly absorbed from stomach

Explanation: A drug with a pKa of 7.5 will be mostly ionized in the acidic environment of the stomach, leading to poor absorption there, while absorption may improve in the higher pH of the intestine.

Answer: B. Adrenal medulla

Explanation: Pheochromocytoma is a tumor that arises from the chromaffin cells of the adrenal medulla. It is characterized by excessive secretion of catecholamines, leading to symptoms like hypertension and palpitations.

Answer: B. Evans blue

Explanation: Evans blue dye is used as a marker to measure plasma volume because it binds to plasma proteins and remains confined to the vascular compartment, allowing accurate determination of plasma volume.

Answer: C. Adrenaline

Explanation: Adrenaline does not have an intracellular receptor; it binds to membrane-bound G protein-coupled receptors. In contrast, hormones like Vitamin D₃, cortisone, and thyroxin have intracellular receptors that directly modulate gene expression.

Answer: C. Night blindness

Explanation: Vitamin A deficiency primarily results in night blindness, a condition where the eyes struggle to adjust to low-light conditions. This deficiency can also lead to other ocular and systemic problems if left untreated.

Answer: B. Ca binding troponin I

Explanation: In cardiac muscle, contraction is triggered by the binding of calcium ions to troponin I, which leads to conformational changes in the troponin complex and facilitates the interaction of actin and myosin.

Answer: A. Folic acid

Explanation: Folic acid supplementation before and during early pregnancy is crucial to prevent neural tube defects like spina bifida. Adequate folic acid intake ensures proper cell division and neural tube closure in the developing embryo.