৪৯তম বিসিএস ⎯ প্রাণ রসায়ন [৬০১]

Answer: C) Hemoglobin
Explanation: Plasma consists mainly of water, electrolytes, nutrients, hormones, and plasma proteins (like albumin, fibrinogen). Hemoglobin is found inside red blood cells, not in plasma.

Answer: B) Maintain osmotic pressure
Explanation: Albumin helps maintain colloidal osmotic pressure and prevents edema by retaining fluid within blood vessels.

Answer: B) Fibrinogen
Explanation: Fibrinogen is converted into fibrin during the coagulation process, forming a blood clot.

Answer: C) 7.35–7.45
Explanation: Human blood is slightly alkaline, maintaining a narrow pH range essential for enzyme activity and cellular functions.

Answer: D) 120 days
Explanation: RBCs survive about 120 days in circulation before being destroyed in the spleen and liver.

Answer: B) Neutrophils
Explanation: Neutrophils make up about 60–70% of total WBCs and are the first line of defense against bacterial infections.

Answer: B) Liver and spleen
Explanation: Macrophages in the liver and spleen phagocytose and break down old or damaged RBCs.

Answer: C) Groups A, B, AB, and O
Explanation: AB blood group individuals are universal recipients because they lack anti-A and anti-B antibodies.

Answer: C) O-
Explanation: O- blood lacks A, B, and Rh antigens, making it safe for transfusion to any recipient.

Answer: B) It can cause hemolytic disease of the newborn
Explanation: Rh incompatibility between mother and fetus can lead to hemolytic disease of the newborn due to maternal anti-Rh antibodies.

Answer: D) Left ventricle
Explanation: The left ventricle pumps oxygen-rich blood into the aorta for systemic circulation.

Answer: C) Mitral (bicuspid) valve
Explanation: The mitral valve allows blood flow from the left atrium to the left ventricle and prevents backflow.

Answer: C) SA node
Explanation: The sinoatrial (SA) node initiates electrical impulses that regulate the heartbeat.

Answer: B) Accumulation of lipid plaques in arteries
Explanation: Atherosclerosis is caused by deposition of cholesterol and lipids in arterial walls, narrowing the lumen.

Answer: C) Smoking
Explanation: Smoking increases the risk of plaque formation and vascular damage, contributing to coronary artery disease.

Answer: B) Heart attack
Explanation: Myocardial infarction (MI) occurs due to blockage of coronary blood flow, leading to death of heart muscle tissue.

Answer: B) Creatine kinase-MB (CK-MB)
Explanation: CK-MB is released into the blood when heart muscle is damaged, serving as a diagnostic marker for MI.

Answer: A) Mouth → Esophagus → Stomach → Small intestine → Large intestine
Explanation: The correct anatomical order is mouth → pharynx → esophagus → stomach → small intestine → large intestine → rectum.

Answer: C) Transport food to the stomach
Explanation: The esophagus is a muscular tube that moves food from the pharynx to the stomach via peristalsis, without digestion.

Answer: B) Small intestine
Explanation: Villi and microvilli increase the surface area for nutrient absorption in the small intestine.

Answer: C) Cecum
Explanation: The appendix is a small, finger-like projection attached to the cecum, which is the first part of the large intestine.

Answer: B) Absorb water and electrolytes
Explanation: The large intestine primarily absorbs water and salts, and forms feces.

Answer: B) Amylase
Explanation: Salivary amylase (ptyalin) initiates carbohydrate digestion by breaking down starch into maltose.

Answer: B) Parietal cells
Explanation: Parietal cells secrete HCl, which activates pepsinogen and kills harmful microorganisms.

Answer: C) Bile
Explanation: Bile is secreted by the liver and stored in the gallbladder. The pancreas produces digestive enzymes like lipase, amylase, and trypsinogen.

Answer: B) Emulsification of fats
Explanation: Bile salts break down large fat globules into smaller droplets, aiding pancreatic lipase activity.

Answer: C) Monosaccharides
Explanation: Carbohydrates are fully broken down into monosaccharides like glucose, fructose, and galactose for absorption.

Answer: C) Active transport with sodium
Explanation: Glucose absorption involves sodium-dependent active transport via SGLT-1 transporters.

Answer: C) Jejunum and ileum
Explanation: The jejunum and ileum contain numerous villi and microvilli, making them the primary sites for nutrient absorption.

Answer: B) Lactase
Explanation: Lactase breaks lactose into glucose and galactose in the small intestine.

answer: C) Lobule
Explanation: The liver is made up of hexagonal lobules, each consisting of hepatocytes arranged around a central vein.

Answer: A) Enterokinase

Explanation: Enterokinase, secreted by the intestinal mucosa, activates trypsinogen to trypsin.

Answer: B) Pancreatic enzymes and brush-border enzymes
Explanation: Enzymes like trypsin, chymotrypsin, and peptidases break down proteins into amino acids for absorption.

Answer: C) Secretion of insulin
Explanation:
Insulin is secreted by the pancreas, not the liver. The liver synthesizes plasma proteins like albumin and clotting factors.

Answer: B) Emulsify fats
Explanation:
Bile salts break large fat globules into smaller droplets, increasing the surface area for pancreatic lipase to act.

Answer: B) Portal vein
Explanation:
The hepatic portal vein brings nutrient-rich but oxygen-poor blood from the gastrointestinal tract to the liver for processing.

Answer: B) Glucuronyl transferase
Explanation: This enzyme conjugates bilirubin with glucuronic acid to make it water-soluble for excretion in bile.

Answer: B) Jaundice
Explanation: Buildup of bilirubin in the blood leads to jaundice, characterized by yellowing of the skin and eyes.

Answer: B) Alveolus
Explanation: Alveoli are tiny air sacs where gas exchange between air and blood occurs.

Answer: B) Epiglottis
Explanation:
The epiglottis closes over the trachea during swallowing, directing food into the esophagus.

Answer: B) Simple diffusion
Explanation:
Oxygen and carbon dioxide move across the alveolar membrane by simple diffusion due to concentration gradients.

Answer: C) Emphysema
Explanation: In emphysema, alveoli are destroyed, reducing the surface area for oxygen exchange, leading to breathing difficulties.

Answer: B) 100 mmHg
Explanation:
The alveolar oxygen partial pressure is about 100 mmHg, which drives oxygen diffusion into the blood.

Answer: B) Afferent arteriole
Explanation:
The afferent arteriole brings blood to the glomerulus for filtration.

Answer: C) Filtration
Explanation:
The glomerulus filters blood plasma, initiating urine formation.

Answer: B) Antidiuretic hormone (ADH)
Explanation:
ADH increases water reabsorption, reducing urine output and preventing dehydration.

Answer: B) Sodium
Explanation:
Aldosterone promotes sodium reabsorption, which helps maintain blood pressure and water balance.

Answer: C) Loop of Henle
Explanation: The part of the nephron responsible for countercurrent multiplication is the loop of Henle. This U-shaped tubule, particularly in juxtamedullary nephrons that extend deep into the renal medulla, creates a concentration gradient in the surrounding interstitial fluid. This gradient is crucial for the kidneys' ability to produce concentrated urine and conserve water.

The process relies on the distinct properties of the loop's two limbs: 

Descending limb: This part is highly permeable to water but impermeable to solutes. As the filtrate moves down into the hypertonic medulla, water leaves the tubule by osmosis, concentrating the filtrate.

 
Ascending limb: This part is impermeable to water. It actively pumps out solutes, primarily sodium and chloride ions, into the interstitial fluid. This action is what "multiplies" the concentration gradient, making the medulla even more hypertonic and pulling more water out of the descending limb.
The vasa recta, a network of capillaries that runs parallel to the loop of Henle, also plays a key role in maintaining this concentration gradient through a process called countercurrent exchange, preventing the solutes from being washed away.


https://www.youtube.com/watch?v=hjQd9nWAxQk

Answer: C) Urea
Explanation:
Urea, produced from protein metabolism in human, is the major nitrogenous waste in urine.

Answer: C) Erythropoietin
Explanation:
Erythropoietin stimulates the bone marrow to produce red blood cells in response to low oxygen levels.